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I have a '95 FD, '99 spec twins on 10psi with a PFC. The car has 120,800 miles on it, by the PO's records the motor just hit 60,800 miles.
The car just came back over the weekend from a reputable shop (for fuel pulsation damper leak & vacuum hose job) and is now giving me strange symptoms.
Symptoms:
On startup, hot or cold, the front rotor struggles to fire. It feels like the car is running on one rotor for 30 seconds at 650ish RPM until it finally settles at 1100-1200RPM as typical.
At 61C, when the throttle body thermowax opens, it struggles to maintain its 750RPM target.
At full warmup (>81C), it actually idles perfectly fine, and at 85C when the fans are told to kick on, it E/L idles fine as well.
If I try and drive low load between 61C and full warmup, the car would struggle to idle and almost die without throttle.
If I drive fully warm, the car still idles, drives, cruises, and boosts really well.
On cold startup, it blows a ton of white, thin, steam-like smoke. This is continual until about halfway to op temp, when it starts clearing up.
Before dropping it off at the shop, it would puff one little puff of smoke on startup and idle cleanly at 1500RPM until the thermowax opened up.
I'm getting a good amount of white foam at the bottom of my oil filler cap, and down in the oil fill neck. I checked after a hot drive, there is no visible foam on the dipstick, which I hear is the real trouble signal.
I pulled my spark plugs hoping it was an ignition issue (maybe a dying plug couldn't ignite the cold startup enrichment?) and the L1 plug was super fried and had some wet residue on the threads. It was hard to tell what it was, the plug smelled like gas but the threads smelled a little sweet.
When I got the car back from the shop, after about 150miles of driving, I noticed the coolant reservoir was a tick below the L line. I know that the UIM had to come out which was off to do vacuum hoses which likely means a coolant change at the shop.
I have refilled the reservoir to between L and F. After a bit more driving, the levels at the reservoir haven't dropped enough for me to notice. I am not getting gurgling or coolant puking out of my reservoir.
Questions:
I'm getting a lot of feedbackthat I'm experiencing the start of coolant seal failure in rotor 1, and that the rotor is struggling to fire because the chamber needs to clear out coolant.
1) What's my best way of diagnosing this?
Compression test: I would expect to see three low compression numbers from rotor 1, but it feels like, with the car running fine while hot, the leak might not be big enough to give me meaningfully low compression?
Coolant pressure test: If I pressure test the cooling system cold, when I expect the leak to happen, how will I know if the leak is internal to the engine versus an external leak that maybe I can't visibly see? If my system can't hold pressure, and I can't see anywhere along the system where there's a leak, is the obvious conclusion that it's an engine-internal leak?
How can I test that it is not a turbo seal failing and puffing out oil instead?
2) How much time does my motor have left on it? Some people say their car has been giving them these signs for years and they just deal with it, that maybe a rebuild is now on the horizon but it's not immediate.
Do I risk damaging any components continuing to drive the car casually, point A to point A? Or is my best course to stop driving the car now to save the hard parts I know are still good and expect to rebuild ASAP?
Clarifications:
The car was in the shop for a fuel leak at the FPD. I know we're in the age of "trusted" rotary shops falling under the microscope and being scrutinized. I want to be clear that that isn't the case here.
The shop replaced the FPR, FPD, cleaned and tested both my primaries and my secondaries, and replaced the injector O-rings. For precaution, they replaced my Denso fuel pump with an Aeromotive 340LPH pump.
The shop replaced one of my O2 sensors for an AEMX wideband AFR gauge (O2 feedback has been off since I bought the car and the emissions equipment may or may not be absent).
The shop had a discussion with me over the phone before my appointment telling me exactly what tests they were going to run, that they would sweep my powerband to check AFRs. I've agreed to all of them.
I have a front/rear combination dash cam installed on the car powered by ignition.
I've reviewed the footage and all captured testing is something I've agreed for them to do. No where in the footage does it seem like they flogged or abused my motor.
I can see where the car started producing tons of smoke on my rear camera, though. This was during a test where the shop was holding an RPM to verify AFR.
I would absolutely work with this shop again. Daleclarks' "Rebuilding the engine yourself" thread is making me consider trying to rebuild this with my uncle, who is a very tenured UPS mechanic. Everyone seems to have a positive experience putting the car back together themselves and I'm a little excited to have the opportunity to do it too.
But I'm jumping ahead of myself. I'd like to diagnose that it is the motor before deciding on how to replace the motor.
OK, first things first is we got to see how the engine is health-wise. I think there may be some external things going on too, but let's find out how the motor is.
With the car stone cold, pull the EGI fuse and pull the front leading plug. Have someone help out, gas pedal to the floor and have them crank the car over. Put a white paper towel over the leading spark plug hole and see what comes out. Do the same for the rear rotor.
If you have coolant pooling in the engine you should get some coolant on the paper towel when cranking. Coolant has a very distinct smell and it may even be green on the towel. You can also do some other tests like the champagne bubble test and use one of those testers that changes color if there are exhaust gasses in the coolant.
Also worth doing a compression test with a rotary compression tester. This will let you know the general health and compression of the engine.
The wanting to stall or die while warming up I think is possibly the coolant temp correction in the PFC needing some love. If you have a Commander you may be able to mess with it and see if you can get it happier.
If you DO have a coolant seal failure the engine will likely be a great rebuild candidate. Many that I have done literally needed new coolant seals or, worst case, a new iron because the wall behind the seal had failed. This means you can re-use all the major hard parts. Put new apex seals and whatnot in, hand-fit side seals, and you'd have a great, solid engine.
The foam or water in the oil cap or dipstick I've never really found to be a good indictor of anything on a rotary. Many times you get condensation on the cap from short drive cycles. Also the coolant mores goes in the combustion chamber to be burned, not really getting in the oil.
I pulled the EGI fuse and unplugged my coils, had my brother who was visiting crank the car while I checked for coolant in the chambers with a paper towel. Absolutely nothing came out of the holes. Annoying!
By this point, the car had been sitting a week since its last start. I figure I should've gotten at least some fluid on the paper towel if there were a leak. We fired the car up after putting everything back together and it fired up like normal. It is still smoking more than it used to, but it was running on both rotors and holding the right RPMs. I gave it a good heat cycle around the neighborhood and parked it.
I waited 10 minutes as it was cooling down, and re-started the car hot, it started on just one rotor again, but it wasn't shoveling any smoke out the back. After about 30 seconds, it cleared up and idled as normal.
I suspected that, if there was a coolant leak into the motor, it would make sense the car would start fine after we cranked it over to check the chambers. Maybe by cranking it, we had shoveled all the coolant in the chambers into the exhaust, which helped the car fire?
I waited until the next day to start the car again, with the intent of letting coolant seep into the chamber overnight and give me a choppy start.
I went into my PFC commander and knocked down the multipliers in the coolant correction table. When I went to start the car again, it started up as usual, firing on both rotors. Annoying.
I drove the same route around the neighborhood to properly heat cycle the motor again.
Like last time, I parked the car and waited 5 minutes before hot re-starting it. Again, it only fired on one rotor.
I know it's not conclusive, but I think the motor might be ok and this might be an issue with the newer, stronger pump.
Part of the visit to the shop was to fix a fuel leak at the FPD (both the FPD and FPR were replaced with stock parts) and to pre-emptively change the stock 255LPH pump with an Aeromotive 340LPH pump, and to install a fuel pump harness to keep voltage constant at the pump.
With the car starting happily at cold cranking, and my paper towel test coming back dry from both the front and back rotor, is it possible this stronger pump is pressurizing my fuel system more, and pushing more fuel into the engine than it can fire?
I know there is the PRC solenoid, which increases fuel pressure at hot start. It would explain why the car is happy to start cold but unhappy hot.
Tonight I plan to stop by O'Reilly and rent a sniffer test for the coolant. I'll syphon some of the coolant out of the filler neck, run the car cold to hot and see if it smells any combustion gasses.
I think it might also be worth doing a coolant pressure test. How do I do this with two caps? It makes sense to install the tester at the AST, would I just test at a lower pressure than the rad caps' 12psi?
I was hoping my compression tester would have arrived by now - I ordered it last Tuesday hoping to use it over the weekend. UPS says it'll arrive tonight (Tuesday), so if it's at home when I get off work, I do a compression test, too.
When cranking the car, I felt three strong pulses from both front and rear rotors as I was holding the paper towel over it. Nothing is certain until it's certain.
If the car passes with no combustion gasses in the coolant and no pressure loss over 20 minutes, I'm happy to say it's a fuel issue.
The car has been driven about 70 miles over three trips since I started testing everything. After all three drives, with the car stone cold, the level in the coolant overflow has not moved a single tick. It is still perfectly in that middle tick between F and L.
The coolant temperature behavior while driving is also still consistent with how it used to behave - hovering around 81C-82C, maxing out at 85C before the fans kick on and drop it down to 81C.
Again, nothing is certain until it's certain, but I'm hopeful for good news.
The latest 1-rotor hot start sounds like a leaking fuel injector. Fuel gets in the combustion chamber and takes a while to clear out. That might also account for the increase in smoke.
Thanks for the response, Dave. I think that's definitely possible.
I got on the phone with the shop. I have an appointment to come back on Thursday and have them check over their work - part of the job was to flow test and clean injectors, and install new O-rings. If it is a fuel injector issue, which should have been checked anyway, they should be able to re-do that for me as part of my previous invoice.
Would a leaky injector not also cause a lopey 1-rotor cold start, as well? I assume leaking fuel doesn't evaporate in a closed chamber overnight.
I do think the smoke is fuel related - I might be seeing a mix of condensation and just the burning of premix in the way too much fuel at startup. The smoke smells like burning rubber more than it smells sweet. Again, nothing is certain until it's certain, so I'll continue to do the coolant pressure, sniffer, and engine compression tests to be sure.
OK, first things first is we got to see how the engine is health-wise. I think there may be some external things going on too, but let's find out how the motor is.
With the car stone cold, pull the EGI fuse and pull the front leading plug. Have someone help out, gas pedal to the floor and have them crank the car over. Put a white paper towel over the leading spark plug hole and see what comes out. Do the same for the rear rotor.
If you have coolant pooling in the engine you should get some coolant on the paper towel when cranking. Coolant has a very distinct smell and it may even be green on the towel. You can also do some other tests like the champagne bubble test and use one of those testers that changes color if there are exhaust gasses in the coolant.
Also worth doing a compression test with a rotary compression tester. This will let you know the general health and compression of the engine.
And if you don't have access to a rotary tester, take a slow motion video of a piston engine compression tester with the release valve held down.
Or just listen to the pulses. A staccato rhythm is bad news.
I have a '95 FD, '99 spec twins on 10psi with a PFC. The car has 120,800 miles on it, by the PO's records the motor just hit 60,800 miles.
The car just came back over the weekend from a reputable shop (for fuel pulsation damper leak & vacuum hose job) and is now giving me strange symptoms.
Symptoms:
On startup, hot or cold, the front rotor struggles to fire. It feels like the car is running on one rotor for 30 seconds at 650ish RPM until it finally settles at 1100-1200RPM as typical.
At 61C, when the throttle body thermowax opens, it struggles to maintain its 750RPM target.
At full warmup (>81C), it actually idles perfectly fine, and at 85C when the fans are told to kick on, it E/L idles fine as well.
If I try and drive low load between 61C and full warmup, the car would struggle to idle and almost die without throttle.
If I drive fully warm, the car still idles, drives, cruises, and boosts really well.
On cold startup, it blows a ton of white, thin, steam-like smoke. This is continual until about halfway to op temp, when it starts clearing up.
Before dropping it off at the shop, it would puff one little puff of smoke on startup and idle cleanly at 1500RPM until the thermowax opened up.
I'm getting a good amount of white foam at the bottom of my oil filler cap, and down in the oil fill neck. I checked after a hot drive, there is no visible foam on the dipstick, which I hear is the real trouble signal.
I pulled my spark plugs hoping it was an ignition issue (maybe a dying plug couldn't ignite the cold startup enrichment?) and the L1 plug was super fried and had some wet residue on the threads. It was hard to tell what it was, the plug smelled like gas but the threads smelled a little sweet.
When I got the car back from the shop, after about 150miles of driving, I noticed the coolant reservoir was a tick below the L line. I know that the UIM had to come out which was off to do vacuum hoses which likely means a coolant change at the shop.
I have refilled the reservoir to between L and F. After a bit more driving, the levels at the reservoir haven't dropped enough for me to notice. I am not getting gurgling or coolant puking out of my reservoir.
Questions:
I'm getting a lot of feedbackthat I'm experiencing the start of coolant seal failure in rotor 1, and that the rotor is struggling to fire because the chamber needs to clear out coolant.
1) What's my best way of diagnosing this?
Compression test: I would expect to see three low compression numbers from rotor 1, but it feels like, with the car running fine while hot, the leak might not be big enough to give me meaningfully low compression?
Coolant pressure test: If I pressure test the cooling system cold, when I expect the leak to happen, how will I know if the leak is internal to the engine versus an external leak that maybe I can't visibly see? If my system can't hold pressure, and I can't see anywhere along the system where there's a leak, is the obvious conclusion that it's an engine-internal leak?
How can I test that it is not a turbo seal failing and puffing out oil instead?
2) How much time does my motor have left on it? Some people say their car has been giving them these signs for years and they just deal with it, that maybe a rebuild is now on the horizon but it's not immediate.
Do I risk damaging any components continuing to drive the car casually, point A to point A? Or is my best course to stop driving the car now to save the hard parts I know are still good and expect to rebuild ASAP?
Clarifications:
The car was in the shop for a fuel leak at the FPD. I know we're in the age of "trusted" rotary shops falling under the microscope and being scrutinized. I want to be clear that that isn't the case here.
The shop replaced the FPR, FPD, cleaned and tested both my primaries and my secondaries, and replaced the injector O-rings. For precaution, they replaced my Denso fuel pump with an Aeromotive 340LPH pump.
The shop replaced one of my O2 sensors for an AEMX wideband AFR gauge (O2 feedback has been off since I bought the car and the emissions equipment may or may not be absent).
The shop had a discussion with me over the phone before my appointment telling me exactly what tests they were going to run, that they would sweep my powerband to check AFRs. I've agreed to all of them.
I have a front/rear combination dash cam installed on the car powered by ignition.
I've reviewed the footage and all captured testing is something I've agreed for them to do. No where in the footage does it seem like they flogged or abused my motor.
I can see where the car started producing tons of smoke on my rear camera, though. This was during a test where the shop was holding an RPM to verify AFR.
I would absolutely work with this shop again. Daleclarks' "Rebuilding the engine yourself" thread is making me consider trying to rebuild this with my uncle, who is a very tenured UPS mechanic. Everyone seems to have a positive experience putting the car back together themselves and I'm a little excited to have the opportunity to do it too.
But I'm jumping ahead of myself. I'd like to diagnose that it is the motor before deciding on how to replace the motor.
-Jason
Did they leak test the injectors, or just clean and bench test them? If you have a leaky injector like has been mentioned as a possibility, I would think upgrading the fuel pump might exacerbate this. Though maybe the FPR means that the extra flow is irrelevant?
Thank you for your comment, Valkyrie. The FPR making the extra fuel flow irrelevant was also my question. The car was in for a fuel leak, so I would think fuel pressure testing the fuel system would've been part of the visit. I did not see a test like that performed on my dashcam, because the hood was up the whole time. I will ask on my shop visit on Thursday.
Not super great news.
Cooling System Pressure
I rented this pressure cap tester from O'Reilly. The cap on my AST is 13 PSI so I pumped the cooling system up to 15 expecting it to drop somewhere around 13psi and hold. I came back 8 minutes later and it had dropped to around 10-11psi. I used the adapter circled in red, and tested at the filler neck. I did see the level on my overflow go up. When I started the car, it still fired on both rotors, confusingly enough. It did not smoke more than usual. Confusingly, it was a little less.
My car has a Pettit AST with one of those LEV-R Vent caps that I don't like. Maybe it was a bad cap, maybe not. I will buy a new cap tomorrow for the AST and test again, that should rule it out for certain.
Cooling System Sniffer Test
I pushed the car out of the garage and started it with the filler cap off. I rented this combustion gas sniffer from O'Reilly's, too. The fluid is supposed to turn yellow when it smells combustion gasses. I siphoned some fluid off the top of the filler neck, but when I started the car, coolant rushed out the filler neck and into the tester. While the car was warming up, I cleaned the tester and added fresh fluid to it. It never turned anything but blue, but I could not pump more than four or five times before the coolant level in the neck came up to the level of the tester and I had to siphon more out. Does it make sense for the coolant filler neck level to rise like that while running? Tomorrow I will siphon out more coolant, about as much to reach the low level sensor, which should buy me time enough to keep the sniffer on for two minutes to continually test.
I drove around the block when it was up to temperature and pulled it in.
I kept the coolant I siphoned in a yogurt container. I measured the amount I siphoned out and poured that amount of new coolant back into the overflow.
I think I'll do a Champaign bubbles test tomorrow.
My compression tester never did arrive. Thanks, USPS. If it doesn't arrive by my shop visit on Thursday, I will have the shop do one for me.
My neighbor across the street came over while the car was warming up and noted that the car sounded different ever since it got back from the shop.
Thank you for your comment, Valkyrie. The FPR making the extra fuel flow irrelevant was also my question. The car was in for a fuel leak, so I would think fuel pressure testing the fuel system would've been part of the visit. I did not see a test like that performed on my dashcam, because the hood was up the whole time. I will ask on my shop visit on Thursday.
Not super great news.
Cooling System Pressure
I rented this pressure cap tester from O'Reilly. The cap on my AST is 13 PSI so I pumped the cooling system up to 15 expecting it to drop somewhere around 13psi and hold. I came back 8 minutes later and it had dropped to around 10-11psi. I used the adapter circled in red, and tested at the filler neck. I did see the level on my overflow go up. When I started the car, it still fired on both rotors, confusingly enough. It did not smoke more than usual. Confusingly, it was a little less.
My car has a Pettit AST with one of those LEV-R Vent caps that I don't like. Maybe it was a bad cap, maybe not. I will buy a new cap tomorrow for the AST and test again, that should rule it out for certain.
Cooling System Sniffer Test
I pushed the car out of the garage and started it with the filler cap off. I rented this combustion gas sniffer from O'Reilly's, too. The fluid is supposed to turn yellow when it smells combustion gasses. I siphoned some fluid off the top of the filler neck, but when I started the car, coolant rushed out the filler neck and into the tester. While the car was warming up, I cleaned the tester and added fresh fluid to it. It never turned anything but blue, but I could not pump more than four or five times before the coolant level in the neck came up to the level of the tester and I had to siphon more out. Does it make sense for the coolant filler neck level to rise like that while running? Tomorrow I will siphon out more coolant, about as much to reach the low level sensor, which should buy me time enough to keep the sniffer on for two minutes to continually test.
I drove around the block when it was up to temperature and pulled it in.
I kept the coolant I siphoned in a yogurt container. I measured the amount I siphoned out and poured that amount of new coolant back into the overflow.
I think I'll do a Champaign bubbles test tomorrow.
My compression tester never did arrive. Thanks, USPS. If it doesn't arrive by my shop visit on Thursday, I will have the shop do one for me.
My neighbor across the street came over while the car was warming up and noted that the car sounded different ever since it got back from the shop.
-Jason
Since whatever they did probably involved working with parts that can cause vacuum/boost leaks, maybe try doing a boost leak test?
Clamp a plastic bag (at least two layers) over your intake with a hose clamp and apply air pressure to a vacuum nipple you aren't using.
Spraying soapy water will help pinpoint leaks.
I don't suspect you will find any huge leaks, but you can at least eliminate that possibility.
If you start the car stone cold and coolant shoots out of the filler cap with it off, you have a problem unfortunately.
That typically happens when exhaust gasses are getting into the coolant and pressurizing the coolant system.
Pressurizing the system may not be conclusive since it may not be easily pushing into the combustion chamber when cold but the pressure of the combustion chamber is overcoming the seal and pressurizing the cooling system.
Since whatever they did probably involved working with parts that can cause vacuum/boost leaks, maybe try doing a boost leak test?
Clamp a plastic bag (at least two layers) over your intake with a hose clamp and apply air pressure to a vacuum nipple you aren't using.
Spraying soapy water will help pinpoint leaks.
I don't suspect you will find any huge leaks, but you can at least eliminate that possibility.
Thanks for the comment, Valkyrie. The UIM did have to come off, but I haven't checked for vacuum leaks. With my focus right now on the cooling system, I don't know if a vacuum leak will be what I'm looking for, but it might be worth a shot.
Originally Posted by DaleClark
If you start the car stone cold and coolant shoots out of the filler cap with it off, you have a problem unfortunately.
That typically happens when exhaust gasses are getting into the coolant and pressurizing the coolant system.
Pressurizing the system may not be conclusive since it may not be easily pushing into the combustion chamber when cold but the pressure of the combustion chamber is overcoming the seal and pressurizing the cooling system.
Dale
Thanks, Dale. Should coolant remain still in the filler neck on startup/warmup? It would make sense that, before the T-Stat opens, coolant should just be circulating closed loop. The level rose from a few inches below the filler neck to right at the top and spilling out right at startup, and it kept gradually rising as the car warmed up 30C->75C, when I placed the cap back on the car.
I wonder if it's worth even doing the Lisle funnel and champagne bubble test, I plan on still taking it to the shop tomorrow just to get their opinion since I have the appointment anyway, and maybe have a farewell drive. What a shame! It's driving so well once it's warmed up.
I'll weigh my options for the rest of the week and probably start tearing the engine bay down over the weekend. It might be a good opportunity to start a build thread.
It's funny, when I'm helping my brother with his S2K car problems, it feels incredibly liberating going through the motions, repairing parts and turning bolts. When it's my own car, problems feel way more dreadful. This will be the first engine I've lost owning this car for 4.5 years, and the part of me that's unsure of myself wants to just pay a shop and get the thing over with.
Does it get easier the second time around?
I saw a video recently on the YouTube channel Video Option of Mr. RE Amemiya smiling chatting away while wrenching off tension bolts and an oil pickup off a 13B. I'd love to channel some of his energy while I leave my comfort zone.
Thanks for the comment, Valkyrie. The UIM did have to come off, but I haven't checked for vacuum leaks. With my focus right now on the cooling system, I don't know if a vacuum leak will be what I'm looking for, but it might be worth a shot.
Thanks, Dale. Should coolant remain still in the filler neck on startup/warmup? It would make sense that, before the T-Stat opens, coolant should just be circulating closed loop. The level rose from a few inches below the filler neck to right at the top and spilling out right at startup, and it kept gradually rising as the car warmed up 30C->75C, when I placed the cap back on the car.
I wonder if it's worth even doing the Lisle funnel and champagne bubble test, I plan on still taking it to the shop tomorrow just to get their opinion since I have the appointment anyway, and maybe have a farewell drive. What a shame! It's driving so well once it's warmed up.
I'll weigh my options for the rest of the week and probably start tearing the engine bay down over the weekend. It might be a good opportunity to start a build thread.
It's funny, when I'm helping my brother with his S2K car problems, it feels incredibly liberating going through the motions, repairing parts and turning bolts. When it's my own car, problems feel way more dreadful. This will be the first engine I've lost owning this car for 4.5 years, and the part of me that's unsure of myself wants to just pay a shop and get the thing over with.
Does it get easier the second time around?
I saw a video recently on the YouTube channel Video Option of Mr. RE Amemiya smiling chatting away while wrenching off tension bolts and an oil pickup off a 13B. I'd love to channel some of his energy while I leave my comfort zone.
Every rotary enthusiast should pull and tear their own engine down at least once, if they have the time and space to do it.
I did it with my first RX-7 (which I bought for $400 with a blown coolant seal) and it was a hugely educational experience.
I would have never dared to try it with a DOHC piston engine...
On the upside, having the engine out means you can clean and paint the engine bay...
Every rotary enthusiast should pull and tear their own engine down at least once, if they have the time and space to do it.
I did it with my first RX-7 (which I bought for $400 with a blown coolant seal) and it was a hugely educational experience.
I would have never dared to try it with a DOHC piston engine...
On the upside, having the engine out means you can clean and paint the engine bay...
Thanks for the comment, Valk. You're right 🙂 and I have to remind myself part of the reason I bought this car was to learn. Everyone seems to have positive experience doing this job, so I'm excited to be part of the club.
While waiting on the waitlist for a factory short block from Ray, I decided to re-do some of the testing to just make double sure my problem is really a bad coolant seal.
I felt like I was letting the anxiety of the situation get to me and wanted fresh results now that I've calmed down a bit.
I also just don't feel like I've gotten conclusive evidence that I am having a coolant seal failure?
Compression Test
I got a compression tester from rotarycompressiontester.com. Such a sick tool. Below are values as shown corrected for alt and RPM
Front Rotor 95 98 92
Rear Rotor 106 108 97
(I think I didn't hold the crank down long enough)
The suspected rotor for coolant seal failure is rotor 1. Would something like this even register on a compression test?
Champagne Bubble Test
I know this test isn't usually very conclusive. Here is the car idling and revving a little in my driveway, warming up at around 62C.
As I sit here typing this I wonder if I should have done this while the car was fully warm, with the thermostat open.
Block Tester
Last time I used the block tester, I couldn't get the tester on without coolant filling it, and was scared this meant combustion gasses have been entering the coolant and pushing the coolant into the tester.
I've been wondering since if the coolant level rising as I saw it was just normal expansion of the coolant as the car warmed up. I siphoned out coolant as low as it could go, and then tried the block tester again.
The block tester fluid never changed color, and stayed blue the whole time. I tested from about ambient water temp to around 62*C, when the coolant was getting a little hot for my siphon and I switched to the lisle funnel for the champagne bubble test above.
Rough Re-starts
This all started because of some rough restarts when hot.
Sitting for a few minutes, the car will start rough for about 30 seconds before it finally clears up.
The car eventually clears up (in this case right after I ended my camera video) and idles fine. To me this felt like it was just leaking pressurized coolant into the chamber that needed to burn off.
I got out of the car and noticed a puff of what I thought was white smoke out the exhaust, which cleared up right away as the idle returned to normal.
I sat the car again and had my mom come out to help me film the tailpipe as I restarted it.
It's hard to see in the video, but I'm told while it was choppy it was blowing black smoke.
Conclusions
I am still not sure if I've got the start of a coolant seal failure pushing pressurized coolant into rotor 1 as it sits hot. What can I do to get definitive proof of this, or do any of these things seem like definitive proof? Did I do one of these tests wrong?
The white puff of smoke I saw as I exited my car seemed like it was burning off coolant that accumulated while it was sitting.
The restart with the rough idle and black smoke makes me thing it might be a fuel/tuning issue, as the car is on PFC and just came back from having injectors tested, cleaned, and a new aftermarket fuel pump unit put in.
The shop that did the work has been more than sympathetic and have offered to warranty their work if it is the cause of the car running rough. But I don't want to email them unless I'm absolutely sure what the problem is myself (and, if I'm honest, I'd like to stop relying on shops or other people to work on this car and learn how to handle things myself.)
Let me know your thoughts, I'm more than happy to test something else again tomorrow.
While waiting on the waitlist for a factory short block from Ray, I decided to re-do some of the testing to just make double sure my problem is really a bad coolant seal.
I felt like I was letting the anxiety of the situation get to me and wanted fresh results now that I've calmed down a bit.
I also just don't feel like I've gotten conclusive evidence that I am having a coolant seal failure?
Compression Test
I got a compression tester from rotarycompressiontester.com. Such a sick tool. Below are values as shown corrected for alt and RPM
Front Rotor 95 98 92
Rear Rotor 106 108 97
(I think I didn't hold the crank down long enough)
The suspected rotor for coolant seal failure is rotor 1. Would something like this even register on a compression test?
Champagne Bubble Test
I know this test isn't usually very conclusive. Here is the car idling and revving a little in my driveway, warming up at around 62C.
As I sit here typing this I wonder if I should have done this while the car was fully warm, with the thermostat open.
Block Tester
Last time I used the block tester, I couldn't get the tester on without coolant filling it, and was scared this meant combustion gasses have been entering the coolant and pushing the coolant into the tester.
I've been wondering since if the coolant level rising as I saw it was just normal expansion of the coolant as the car warmed up. I siphoned out coolant as low as it could go, and then tried the block tester again.
The block tester fluid never changed color, and stayed blue the whole time. I tested from about ambient water temp to around 62*C, when the coolant was getting a little hot for my siphon and I switched to the lisle funnel for the champagne bubble test above.
Rough Re-starts
This all started because of some rough restarts when hot.
The car eventually clears up (in this case right after I ended my camera video) and idles fine. To me this felt like it was just leaking pressurized coolant into the chamber that needed to burn off.
I got out of the car and noticed a puff of what I thought was white smoke out the exhaust, which cleared up right away as the idle returned to normal.
It's hard to see in the video, but I'm told while it was choppy it was blowing black smoke.
Conclusions
I am still not sure if I've got the start of a coolant seal failure pushing pressurized coolant into rotor 1 as it sits hot. What can I do to get definitive proof of this, or do any of these things seem like definitive proof? Did I do one of these tests wrong?
The white puff of smoke I saw as I exited my car seemed like it was burning off coolant that accumulated while it was sitting.
The restart with the rough idle and black smoke makes me thing it might be a fuel/tuning issue, as the car is on PFC and just came back from having injectors tested, cleaned, and a new aftermarket fuel pump unit put in.
The shop that did the work has been more than sympathetic and have offered to warranty their work if it is the cause of the car running rough. But I don't want to email them unless I'm absolutely sure what the problem is myself (and, if I'm honest, I'd like to stop relying on shops or other people to work on this car and learn how to handle things myself.)
Let me know your thoughts, I'm more than happy to test something else again tomorrow.
I’m not convinced you even have a coolant issue… or much of an issue at all. At least not one worth replacing the engine for.
Doesn’t the car run fine when it’s hot?
Restarting issues are pretty common for rotaries, since compression is lower when the engine is hot.
I'm concerned because it's doing things it didn't used to before a visit to a rotary shop. It used to be a start and go car. Coming back with a new fuel pump, cleaned injectors, FPD/FPR, and an AFR gauge, now it puffs white smoke while cold and restarts really really poorly. Not like a low compression hot start, where it takes forever to start, but the RPM stumbles to ~600 for like a minute.
It does run fine hot, boosts great, doesn't overheat or dump coolant from the overflow.
Since I got the car back from the shop and noticed the hot start issues back in April, I've driven the car every two weeks and have not lost any coolant or noticed any runniness from my oil.
In the back of my head I wonder if my car was tuned with the old, factory pump, not performing as well as this new aeromotive pump. Maybe the fuel pressure my injectors are seeing is different with this new pump than it was when it was tuned on the old pump/fuel pressure regulator/pulsation damper and it's invalidated my tune? Would that make any sense?
I do know that the car is running kinda rich now that I have the AFR gauge. Nothing crazy but definitely lower AFRs than I have been reading on the forums for other cars*
Black smoke means too much fuel. I'm not familiar with how it's done with a PowerFC, but have you tried changing the fuel map or warm-up fuel settings? If it's idling near 11-12 AFR, try for 12-13 AFR or 13-14 AFR. Remember that misfires will usually read as lean air/fuel mixtures on a wideband O2 sensor, even if the engine is misfiring from an overly-rich fuel mixture.
What makes you say it's only the front rotor that is misfiring, how did you test to prove that?
My RX7 lost a coolant seal around 70k miles, from what I remember the first symptom was losing coolant (low coolant alarm beep), and overheating during long drives, and occasional gurgling sounds in the cabin (presumably air bubbles making their way through the heater core). It would sometimes get the spark plugs wet enough to idle badly for a little while after starting, but I think that sounded different than your videos. Your videos sound more like my engine sounded when I once accidentally added 20% too much fuel to the idle section of the fuel map.
I'm concerned because it's doing things it didn't used to before a visit to a rotary shop. It used to be a start and go car. Coming back with a new fuel pump, cleaned injectors, FPD/FPR, and an AFR gauge, now it puffs white smoke while cold and restarts really really poorly. Not like a low compression hot start, where it takes forever to start, but the RPM stumbles to ~600 for like a minute.
It does run fine hot, boosts great, doesn't overheat or dump coolant from the overflow.
Since I got the car back from the shop and noticed the hot start issues back in April, I've driven the car every two weeks and have not lost any coolant or noticed any runniness from my oil.
In the back of my head I wonder if my car was tuned with the old, factory pump, not performing as well as this new aeromotive pump. Maybe the fuel pressure my injectors are seeing is different with this new pump than it was when it was tuned on the old pump/fuel pressure regulator/pulsation damper and it's invalidated my tune? Would that make any sense?
I do know that the car is running kinda rich now that I have the AFR gauge. Nothing crazy but definitely lower AFRs than I have been reading on the forums for other cars*
You messed with the fuel system and now your car is running rich. Yep, you definitely need a rebuild! Hehehe…
You messed with the fuel system and now your car is running rich. Yep, you definitely need a rebuild! Hehehe…
OK, when you put it like that it does seem pretty open face obvious LOL. I'll see when our next dyno day is to get a retune. It might be worth the money for the seemingly moderate chance its just the tune.
I'm just confused because the fuel pressure regulator was replaced old OEM for new OEM, so even with a new pump the pressure at the rails shouldnt change? Regardless, after doing the testing I'm inclined to just try it and agree, new fuel system calls for new tune.
OK, when you put it like that it does seem pretty open face obvious LOL. I'll see when our next dyno day is to get a retune. It might be worth the money for the seemingly moderate chance its just the tune.
I'm just confused because the fuel pressure regulator was replaced old OEM for new OEM, so even with a new pump the pressure at the rails shouldnt change? Regardless, after doing the testing I'm inclined to just try it and agree, new fuel system calls for new tune.
I'm surprised you weren't already on an aftermarket FPR. I thought it was pretty much mandatory for a tuned engine...
I don't pretend to be an expert on fuel systems, but couldn't 25+ years of metal fatigue could cause your old FPR to deliver different pressure than a brand new one? It's basically a matter of spring tension.
You might not even end up needing much actual tuning. Might be just a few relatively simple adjustments? Probably don't even need to go on a dyno, just need someone with a wideband and a laptop...
If you blow a coolant seal, you'll know! I bought my first RX-7 with a blown coolant seal...
Bad coolant seals typically manifest themselves in different ways.
Most common is the engine taking on water after sitting overnight. Start the car in the morning, car runs rough on initial cold start with some smoke, then clears up as the coolant burns off.
The next symptom is the car continually pushing coolant into the overflow tank and it barfing out of the top. Sometimes that can be a pinhole leak in the hose to the tank but that's a common thing - the cooling system is getting pressurized with engine compression and blowing out.
Also worth hooking up a Lisle funnel, filling it a bit so the level is up where you can see it, then starting it stone cold and seeing what the coolant does. It should just sit there, maybe get sucked in some. If you have it shooting out you got a problem.
Some of these tests you've done on an already warm engine, this all should be done cold.
But it does sound more and more like the car is just not running right fuel-wise. That fuel pump likely richened things up. I'm also not a fan of cleaning stock injectors, I think that just causes more problems than it fixes. Possible one is leaking when it's warm then you get one rotor misfiring until the car warms up.
Sorry for all the downtime. I caught COVID. Not as bad as the flu I had earlier in the year, but definitely inconvenient.
Here is the car with a Lisle funnel on it. I hopped in the car cold start (after 2 weeks of sitting) and ran out to film the level as quickly as I could.
I filled the coolant right to the level of the line where the funnel transitions from a cone to a cylinder. It sucked some in on start up, and seemed to stay rock solid on level throughout warmup.
The coolant level did eventually rise slowly after about 10 minutes of idling. I disconnected the funnel at 64C, around when the high idle started settling to normal idle.
When I reported in an earlier post that the sniffer test was hard to do without keeping coolant from filling it, this was just on the filler neck with no extension or funnel on it. I think the small diameter of the filler neck exaggerated the fluid level changes from just the car running. With the funnel attached, the level stayed very stable.
TL;DR
From here, I've done a compression test with pretty healthy numbers, a sniffer test with no reports of combustion gasses in the coolant, I've verified that the coolant level doesn't change one cold start through warmup. Throughout all the testing and maintenance driving, I haven't noticed a change in coolant level in the reservoir checking cold. I think I'm pretty happy concluding that taking fuel out of the map will alleviate the worries I had with this car.
A new map seems to have brought the car back to how it was before. The running theory is that the (by my estimate) 28 year old FPR was not maintaining the right pressure when the car was tuned in 2018. Replacing that part when it failed with a new OEM one must have been pushing more fuel into the engine on the same map.
I am glad I did not rip out and tear open a good motor. I don't think I would've survived seeing that.
A new map seems to have brought the car back to how it was before. The running theory is that the (by my estimate) 28 year old FPR was not maintaining the right pressure when the car was tuned in 2018. Replacing that part when it failed with a new OEM one must have been pushing more fuel into the engine on the same map.
I am glad I did not rip out and tear open a good motor. I don't think I would've survived seeing that.
Jason
lol… I almost wonder if it didn’t simply need a new tune…
04-11-23, 02:11 PM
