Not good
03-25-21, 01:05 AM
#1
Not good
A little back story first...
- Original motor. 36K miles.
- Bought at 27K, been premixing ~5oz of 2-stroke oil/tank since shortly after purchasing
- Been running water injection for the last 2K miles or so
- I've done a lot of work to the car, but have been careful about keeping safe AFRs and conservative timing with a PFC and datalogit.
- Back around Nov 2020 I installed a "U-type" IC, one that up-sized the stock (2.5"?) inlet and outlet to the same size as the Y-pipe and intake elbow (2.75?") -- point being more airflow.
- On the drive home from doing the IC install at my folk's place, the car overheated. I had forgotten to plug in the radiator fans and was sitting still for a few minutes. I actually had just pulled into a parking spot exactly when the radiator cap popped and steam started blowing out. I immediately pulled out the PFC commander and, if memory serves me, it read 113C (or maybe it was 213F?). Not sure how hot it actually peaked at. This was with the stock radiator cap. I ended up pulling the air box out, plugging the radiator fans back in, and walking to a nearby gas station for some coolant, and then continuing my journey home without issue.
- A few days later, WITHOUT FIRST ADJUSTING TUNE FOR THE NEW IC, I was on a joy ride, at about 1/2-3/4 throttle when a puff of either blue or white smoke came out the tailpipe. I don't recall if it was accompanied by any noise, but it probably was or I wouldn't have noticed.
- Again, the car seemed to run okay since then, but over the past few months it has been developing a hot-start issue. It always starts fine cold, and usually fine hot after a short rest, but if you leave it hot for 20-30 minutes it will often require it to be cranked twice, the second time with a little throttle. I understand that can be caused by several different underlying issues. It does seem as though coolant has been disappearing.
- More recently, the car has been making odd noises at idle. One of them is a creaking noise very similar to th sound cars make as they are cooling down when shut off, but louder and while it's idling. Second, not always, but sometimes, it will make a sort of swishing noise that sounds sort of like a bad belt, but quieter and slightly metallic. I actually just replaced the belts and it's still doing it.
- I installed BNRs and turned the boost up. I have been working on sequential transition issues, not general tuning, but my AFRs are rich in general, especially under boost, and timing is mild. It has been running well while driving.
- Yesterday I went to take it out, and it was difficult to start cold. I let it warm up, as soon as I got on the road and started to give it maybe 1/2 throttle, the motor just bucked and stalled. I repeated this several times, noting that under light throttle, before boost, it would drive fine. I was doing another transition-tuning session, and the target boost was set low, and the conclusion I came to was that over-boost fuel cut was being hit, so after raising my boost settings a bit the car seemed to run completely fine again all of a sudden. I had a fun 1-hour session of pulls between turn-offs on the highway logging data and adjusting PFC boost settings without further issue.
- Today I got in the car to go for another transition-tuning session, and on the first try the car turned over but did not start. The second try the car turned over a time or two, then abruptly stopped with a loud clunk/metal-on-metal sound. 3rd and 4th tries again yielded a few turns and an abrupt clank and halt. Video below.
At this point I pretty well figure my motor is toast (unless the starter is seizing for some reason), but I'm trying to understand what could have happened. My two largest suspects are: 1. overheating and 2. that puff of smoke after installing the new IC. Perhaps the overheating warped a housing and it all started to go downhill from there, until the BNRs did it in.
Any input appreciated.
- Original motor. 36K miles.
- Bought at 27K, been premixing ~5oz of 2-stroke oil/tank since shortly after purchasing
- Been running water injection for the last 2K miles or so
- I've done a lot of work to the car, but have been careful about keeping safe AFRs and conservative timing with a PFC and datalogit.
- Back around Nov 2020 I installed a "U-type" IC, one that up-sized the stock (2.5"?) inlet and outlet to the same size as the Y-pipe and intake elbow (2.75?") -- point being more airflow.
- On the drive home from doing the IC install at my folk's place, the car overheated. I had forgotten to plug in the radiator fans and was sitting still for a few minutes. I actually had just pulled into a parking spot exactly when the radiator cap popped and steam started blowing out. I immediately pulled out the PFC commander and, if memory serves me, it read 113C (or maybe it was 213F?). Not sure how hot it actually peaked at. This was with the stock radiator cap. I ended up pulling the air box out, plugging the radiator fans back in, and walking to a nearby gas station for some coolant, and then continuing my journey home without issue.
- A few days later, WITHOUT FIRST ADJUSTING TUNE FOR THE NEW IC, I was on a joy ride, at about 1/2-3/4 throttle when a puff of either blue or white smoke came out the tailpipe. I don't recall if it was accompanied by any noise, but it probably was or I wouldn't have noticed.
- Again, the car seemed to run okay since then, but over the past few months it has been developing a hot-start issue. It always starts fine cold, and usually fine hot after a short rest, but if you leave it hot for 20-30 minutes it will often require it to be cranked twice, the second time with a little throttle. I understand that can be caused by several different underlying issues. It does seem as though coolant has been disappearing.
- More recently, the car has been making odd noises at idle. One of them is a creaking noise very similar to th sound cars make as they are cooling down when shut off, but louder and while it's idling. Second, not always, but sometimes, it will make a sort of swishing noise that sounds sort of like a bad belt, but quieter and slightly metallic. I actually just replaced the belts and it's still doing it.
- I installed BNRs and turned the boost up. I have been working on sequential transition issues, not general tuning, but my AFRs are rich in general, especially under boost, and timing is mild. It has been running well while driving.
- Yesterday I went to take it out, and it was difficult to start cold. I let it warm up, as soon as I got on the road and started to give it maybe 1/2 throttle, the motor just bucked and stalled. I repeated this several times, noting that under light throttle, before boost, it would drive fine. I was doing another transition-tuning session, and the target boost was set low, and the conclusion I came to was that over-boost fuel cut was being hit, so after raising my boost settings a bit the car seemed to run completely fine again all of a sudden. I had a fun 1-hour session of pulls between turn-offs on the highway logging data and adjusting PFC boost settings without further issue.
- Today I got in the car to go for another transition-tuning session, and on the first try the car turned over but did not start. The second try the car turned over a time or two, then abruptly stopped with a loud clunk/metal-on-metal sound. 3rd and 4th tries again yielded a few turns and an abrupt clank and halt. Video below.
At this point I pretty well figure my motor is toast (unless the starter is seizing for some reason), but I'm trying to understand what could have happened. My two largest suspects are: 1. overheating and 2. that puff of smoke after installing the new IC. Perhaps the overheating warped a housing and it all started to go downhill from there, until the BNRs did it in.
Any input appreciated.
Last edited by mkd; 03-25-21 at 01:28 AM.
03-25-21, 08:30 AM
#2
RX-7 Bad Ass
iTrader: (55)
First off, I think some of the symptoms are unrelated and could be you being hyper-sensitive after the overheating incident.
It's hard to say how far it overheated - once it gets to a certain point, you may not be reading exact coolant temps, you may be reading steam/air. That said, a stock FD would ROUTINELY run at 107 deg. C - that's when the fan switch kicks on.
On engines I've seen that have overheated or have had bad coolant seals it was simply the seal itself that was bad. Depending on where the bad spot is will change how the car reacts. But, typically, you would get coolant slowly leaking into the combustion chamber after a shut off, usually resulting in hard starting in the morning with smoke. Also you have coolant pushed into the overflow tank barfing onto the ground.
Have you tried doing the champagne bubble test yet?
I will watch the video later, can't right now, I'm interested to hear what you are hearing there.
Also a low-mileage engine doesn't mean a perfect engine. It's possible the car sat for a long time with the same coolant in the engine which can do a lot of corrosion damage. That's why I recommend a coolant drain and fill every year with 50/50 distilled water and green Prestone.
Dale
It's hard to say how far it overheated - once it gets to a certain point, you may not be reading exact coolant temps, you may be reading steam/air. That said, a stock FD would ROUTINELY run at 107 deg. C - that's when the fan switch kicks on.
On engines I've seen that have overheated or have had bad coolant seals it was simply the seal itself that was bad. Depending on where the bad spot is will change how the car reacts. But, typically, you would get coolant slowly leaking into the combustion chamber after a shut off, usually resulting in hard starting in the morning with smoke. Also you have coolant pushed into the overflow tank barfing onto the ground.
Have you tried doing the champagne bubble test yet?
I will watch the video later, can't right now, I'm interested to hear what you are hearing there.
Also a low-mileage engine doesn't mean a perfect engine. It's possible the car sat for a long time with the same coolant in the engine which can do a lot of corrosion damage. That's why I recommend a coolant drain and fill every year with 50/50 distilled water and green Prestone.
Dale
03-25-21, 11:31 AM
#3
RX-7 Bad Ass
iTrader: (55)
OK, watched the video.
That sounds like something is Way Bad with the motor. Get a 19mm socket on the front pulley and try and turn it over by hand clockwise. It should turn relatively easily. If not you're locked up somehow - either enough water is in the engine it's hydrolocked or you have a bearing failure of some kind.
If it won't turn over, pull the spark plugs and try to turn it over again. See if water or something comes out of the plug holes.
I've never heard a starter fail like that. Typically they just crank slower and slower then just click without trying to start. If the starter is the same age as the car it's most likely fine - Mazda made good starters that last into the 100,000 mile range.
Dale
That sounds like something is Way Bad with the motor. Get a 19mm socket on the front pulley and try and turn it over by hand clockwise. It should turn relatively easily. If not you're locked up somehow - either enough water is in the engine it's hydrolocked or you have a bearing failure of some kind.
If it won't turn over, pull the spark plugs and try to turn it over again. See if water or something comes out of the plug holes.
I've never heard a starter fail like that. Typically they just crank slower and slower then just click without trying to start. If the starter is the same age as the car it's most likely fine - Mazda made good starters that last into the 100,000 mile range.
Dale
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Redbul (03-25-21)
03-25-21, 10:09 PM
#5
That would be killer if it was just some accessory seizing up. I'll pull the belts off this weekend. Fingers crossed.
The number of turns you get before it halts to a stop it variable, so I kinda doubt it's water locked but I'll pull the plugs off and put a 19mm on it if it's not an accessory.
I worry that it's part of an apex/side/corner seal that is getting wedged in an intake or exhaust port as it turns. Or a bearing. The oil level looks fine. I've been running 20W50 dino juice.
The starter is one of the upgraded Banzai ones. It's like 1.5 years old.
However hot it got was enough to pop the OEM radiator cap. I think the OEM gauge was right around the white mark, so according to the "Big fat cooling thread (https://www.rx7club.com/3rd-generati...thread-571088/) that would be about 121C/250F.
The previous owner (who put 3K miles on it in 24 years! what a psycho!) said that he changed the coolant every 2 years...
Never done the champagne test and can't now as it's not running. Looks like the Mityvac cooling system pressure testers are only $50 so might be a good time to pick one of those up since I have been trying to figure out the hot start issue recently anyway.
The number of turns you get before it halts to a stop it variable, so I kinda doubt it's water locked but I'll pull the plugs off and put a 19mm on it if it's not an accessory.
I worry that it's part of an apex/side/corner seal that is getting wedged in an intake or exhaust port as it turns. Or a bearing. The oil level looks fine. I've been running 20W50 dino juice.
The starter is one of the upgraded Banzai ones. It's like 1.5 years old.
However hot it got was enough to pop the OEM radiator cap. I think the OEM gauge was right around the white mark, so according to the "Big fat cooling thread (https://www.rx7club.com/3rd-generati...thread-571088/) that would be about 121C/250F.
The previous owner (who put 3K miles on it in 24 years! what a psycho!) said that he changed the coolant every 2 years...
Never done the champagne test and can't now as it's not running. Looks like the Mityvac cooling system pressure testers are only $50 so might be a good time to pick one of those up since I have been trying to figure out the hot start issue recently anyway.
03-26-21, 09:25 PM
#6
Long story short it was waterlocked. I had installed a new "ProMeth" AI injection nozzle in the intake elbow, and since I park on an incline the entire 2gal SBG tank drained into the motor. Not sure why this wasn't a problem with the AEM nozzle. At any rate, I will be installing an AEM AI solenoid to prevent this from happening in the future. Good call Dale! The car is dry and running well now.
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DaleClark (03-28-21)
03-27-21, 10:30 AM
#7
Well that's not something you see every day. The AEM nozzle has a check valve inside, I don't know the exact spring value but it should prevent water from flowing when the tank is above the nozzle. The pump makes enough pressure to overcome the check valve.
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03-28-21, 09:51 AM
#10
RX-7 Bad Ass
iTrader: (55)
Yay I called it 
Glad it's something dumb like that and not something worse!
Dale
Glad it's something dumb like that and not something worse!Dale
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