Coolant in the oil. Countdown to a rebuild has begun?
 

The last couple of weeks the car acted like it was flooded on start up but different. Like it was running on one rotor. (I moved the car 10 feet to wash it once and I could barely get it started. Learned my lesson that time.)

I give it a bit of throttle and it clears up and runs great with no issues.

What sort of has me worried is this. After reading this thread:

Bad coolant seal or running rich?

Sgtblue's description of a coolant seal going bad.

My car has been using some coolant the last few weeks. Maybe 6-10oz to top it off at the water neck. I had a coolant buzzer that went off, so I have been checking it each time I drive it.

Tonight, I realized I hadn't checked the oil in a while. Needed to top it up and when I pulled the filler cap, white foam all along the neck. Clearly I have some amount of coolant in the oil. The foam wasn't there a month ago when I changed the oil. No oil that I can see in the coolant. No sweet smell on startup, I am running 50/50. I don't drive it short distances, I try to drive it for at least 20mins + when I take it out.

My car sat in storage for a long time (5-8 years?) before the guy I bought it from got it back up and running (Oct2014). Chassis has 130k, I was told the motor was replaced at 90k, possibly with a used motor. I feel like I am driving around in a ticking time-bomb. :)

Still learning about these motors. Car had/has decent compression (109-113psi) but I guess if it has to come apart it has to be gone through no matter what. Do these motors have main bearings? What other components will be adversely affected if I continue to drive it until the seal inevitably fails.

The car still drives fine with no other issues....yet. Pulls hard, etc.

Thanks for any info


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The condensation in the oil filler neck is probably unrelated to your missing coolant. More testing is required. Champagne test, coolant pressure leak down..etc.

Yeah...that filler neck is no big deal. Now if you drain the oil and it is milky and/or a bunch of water comes out...yeah, then your fawked.
But as you already know in your heart, you just haven't embraced the full horror of it yet, you more than likely have coolant seals leaking. Most of us have been there, done that at one point or another.

Memorial Day weekend, no foam in the oil when I drained it. None on the dip stick now but that probably doesn't mean much. But I was down about a 1/3 of a quart after a few hundred miles. If there was that much water in the oil I would suspect it would read closer to the top.

Will have to look up the champagne test, assume that's the one where you pull the plug and crank the engine looking for water to blow out the spark plug hole. May have to visit a local rotary shop and have the leak down test done.

Every time I leave a parking spot I check for fluids. LOL The car leaves nothing behind but a few drops of oil. I replaced the rad and all the hoses in Feb, other than the hose to the overflow and the one to the TB.

Where's the oil drops coming from?

Typically what happens when the coolant seals are failing is the combustion process overpressurizes the coolant system, forcing coolant into and out the overflow tank.


Then there isn't any coolant available as the car cools to suck back into the system via the thermosiphon effect, hence you see the loss.


How is your overflow tank? Fill it up to the required level once you have the rest of the system filled. There are little hash-marks on its dipstick. Go out for a quick drive, get it up to temperature, then come back and check the tank. If the system is working correctly, it should be HIGHER in the tank as the volume of coolant has expanded due to the heat of it (this is why they are also referred to as "expansion tanks"), but as the car cools, it should draw out of the expansion/overflow tank and return it to the level you filled it to.

Where doesn't it come from? :lol:

Oil pan mostly. Have the brace haven't had the time to put it in. Rear main seal replaced with clutch. Filter stand O-rings replaced. Sending unit resealed. Somewhere higher on the motor than those two things is leaking, towards the back. Oil Injectors? Oil filler neck? Front right of the motor, OMP? Not too bad over there, probably needs new washers. I have a nice coating of oil all the way back past my mid-pipe so at least I know my car isn't going to rust anytime soon. :)

Will check this closer the next time out. Its got coolant in it but I haven't been monitoring it. I know how the system is supposed to function so you are right starting with the simple things is always the best course. AST is new, caps are both new. Only the one on the AST is a pressure cap.

I have about 20 years knowledge of working on all type of piston cars. LOL. NOt a mechanic, just an enthusiast.

There needs to be a .9 bar pressure cap on the filler, also.

Why would I need pressure caps on both? I thought when running an AST you only ran one on the AST.

Factory setup, remember what the AST's function is.

Hmm, now I am confused. When I first bought the car it didn't have an AST. It had what I guess was an ASP delete, Turbo II setup on the water neck with a .9 bar cap. A lot of gurgling in the heater core.

So I added the AST and from the research I had done, thought I needed just a cap for the water neck. The mazda parts diagram I was looking at showed a non-press cap for the water neck, so that's what I ordered. I still have the other .9 bar cap.

A pressure cap will fit the oem filler neck location, but doesn't do anything extra beyond sealing the top closed just like a factory fill cap does.

Nope.


It won't hurt anything, but it isn't supposed to be there.

Did some more investigating. Looking through the RH duct opening in the bumper, it looks like there is some residual fluid below the overflow tank. Could have been there a long time or more recently, hard to tell. Something to check the next time out. Also, the coolant level sitting on the expansion tank cold is at the top of the hash marks. I can also see about a 1/4" of brown crud in the tank. I flushed out the motor and heater core, didn't think to hit the plastic tank. Being that's its buried I assume the only way to get it out would be to pull the front bumper? Or is there another way.

So I guess there is still the potential that the coolant is expanding over to the tank and not returning as the system cools as it should. Boy I sure hope so. Will post back, probably not until next week.

You can get to the Coolant overflow tank by removing the front passenger side wheel and fender liner..... leave the bumper on ;)

Phew! I always assume the worst with this car, but I must persevere. :)

Yes, carefully inspect the hoses between the AST and overflow. Or even just replace them, probably time for that to be done anyway even if you do end up needing a rebuild. The slightest pinhole leak will result in failure to pull coolant back into the engine.

Pulled the expansion tank. There was definitely a few drips of coolant on the lower tray and a moist color to the general area. Signs of overflow while moving. Will order the hoses tomorrow.

The small black grommet next to the opening the filler neck slides into is just an overflow for the tank, correct? I am not missing anything else?


https://cimg7.ibsrv.net/gimg/www.rx7...b1aa0772f3.jpg

Nothing goes there that I know of.

If coolant is coming out of that hole then you have too much coolant!

Right, IF. I originally topped the system off a few times because my coolant buzzer was going off. The coolant must have been going somewhere and I am going to assume it was not being drawn back into the system. But I never saw coolant under the car, in my garage or elsewhere. Will get it buttoned back up this week and pay close attention to this area as well as the exact levels in the overflow.

Yeah...I went back thru the parts diagram and came to the same conclusion, lol!


Sorry, o.p., if I caused any confusion... :blush:

NP, I thought I was right either way. LOL

It will be a long time before I claim to be any kind of rotary expert that's for sure.

Update
 

Pulled the fender liner and expansion tank and cleaned it out.

Installed new AST to tank hose, was a little short for the location of my AST, so I used one of the white plastic couplers from the old hose to extend it 5" or so.

Added some coolant to the expansion tank, ended up almost halfway between L and F or whatever the letters were on the dipstick. Marked the tank with a sharpie.

Topped off the water neck, to the top.

Started the car and my coolant buzzer came on (son-of-a). Popped the cap off, car had been idling maybe 2 mins, a small amount of coolant spilled out the top, put the cap back on, buzzer still on.

Started driving, buzzer shut off after 4 mins or so.

Drove on the HW for about 30 mins. Pulled in the garage and shut her down. Listened /watched the coolant expand into the tank. It went up about an inch and a half which ended up a notch or two above full. Marked the tank with a sharpie.

Car has been sitting for 3 hours. Water neck is still 100+ degree, infrared thermo.

Expansion tank level has now dropped down almost half an inch.

Will check the water neck level tomor when its dead cold.

just a cross the T question, but since the water level sensor is right under the cap on the thermostat, that is the one you're checking?

Yes, just above the sensor. That's why it was weird. The AST was full as well.

So I am lost now (again).

Just checked the expansion tank. The coolant level continued to drop to about half way from where it was when I shut it down. Conclusion, coolant is being drawn back into the system???? It went up, it went back down. Just not all the way down, there is more coolant in the tank than when I started out.

Open the water neck/thermo housing. Empty down to the sensor. You can see the top of the sensor. AST is down about an inch from when I left.

Others have mentioned their thermo housing is always full. Mine has never really been full under normal operation, I always have to look down to see the coolant.

As soon as I shut the car down, I hear a gurgling coming from near or under the intake manifold. Like percolating. Another observation is usually when I pull away from a stop I can hear the coolant (and maybe air) being pushed through the heater core. Both of these things have occurred since I have owned the car. (Nov 2014)

I burped the system a number of times. And I figured any residual air would be taken care of by the AST, since that's what the name implies. :)

What do I do now? Top off the system and repeat the cycle?

What kind of AST do you have?

Coolant tends to boil near the exhaust sleeves on shut down. One of the side-effects of mazda putting a 13psi cap on the system after the recall.

Aftermarket alum. Bought it new in the FS section. SR motorsports maybe. The cap says 16v with no other markings so it could be a 16lb?

That probably is a 16psi cap.

If it's anything like the Pettit AST.... mine would allow antifreeze to flow freely into the overflow tank as I poured it into the filler cap on the engine. Tried a different pressure cap, same problem. Deleted AST...no more problem.

Some of the ASTs with a billet cap flange are much less problem-prone.

Personally I'm a big fan of Evans NPG+ with a zero pressure cap..... that's not easily converted to but worth discussing next time we meet up :)

Consider bringing it by IRP for Mr. Huk to take a look.

Silly question, but have you ensured that all your coolant hose clamps are tight?

So here is a pic of the setup. I know if I fill the thermo neck to the top the coolant travels over and fills the AST if the cap is off.

When I bought the car I knew nothing about FDs, it had the AST deleted and the expansion wasn't even plumbed. So I figured I would go back to as close to stock as it could be.

Just drove it about an hour or so. Topped up the thermo housing before I left. It took about 7oz of coolant. Stopped once for about 15 mins for ice cream.

Just pulled it in. The expansion tank now has another inch of coolant in it, so its roughly 3 inches higher than when I started 'logging' it yesterday. Once it cools I assume it will drop, but either way I now have probably close to 16-24oz of fluid in that tank that wasn't there two days ago.


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Did almost every cooling hose this winter (skipped the TB hose). They are all tight. I have no visible leaks that I can find nor any coolant on the ground. Unless there is some tiny spot where its leaking and evaporating instantly say on an exhaust mani. But I would think I would see steam and/or smell it. Like when my rad almost blew at your shop this winter. LOL

I will be at IRP as soon as we can coordinate our schedules. :) I need to have him look it over in case its something really obvious I am missing. Also going to have him pressure test the system.

I read a few of the evans threads on here. It didn't seem like an overwhelming amount of people thought it was best for these engines.

Thanks for hanging in with me everyone. Clearly these cars are not for the faint of heart. I am only 7 months into this odyssey.

Checked the tank this morning. Coolant was once again drawn back into the system. But just like the last cycle, there is more coolant in the tank than previously. And the thermo housing was empty down to the sensor. Pretty much the exact results from the day before. So I have to assume if I add 8oz per cycle it will keep accumulating in the expansion tank and eventually overflow.

I have the parts to eliminate the AST so that may be my next option.

Have you tried replacing the pressure cap? Cheap part that essentially controls flow to and from the reservoir.

if it pushes coolant out, but doesn't pull it back in, you probably have a leak somewhere, and it just needs to be big enough to bleed away the vacuum. i'd say pressure testing of the system is in order

So Ihor pressure checked the system today. No obvious leaks. A small weep at the the rad from the AST to rad line. We tightened the clamp up. When I started it up after the test there was no smoke from the tailpipe. So he is not 100% convinced its a coolant seal.....yet.

I have the correct FC cap/neck piece to eliminate the AST so I may throw that back on.

My expansion tank is overflowing now and the system is low in the AST and the waterneck.

On a side note, when I bought the AST I had it shipped to a family member where the car was at the time. The fittings were not properly welded so we asked for a second one. Who knows, maybe the AST is the issue.

The leak at the bypass hose to the radiator looked enough to be a culprit. Let me know if tightening it makes any difference. As we discussed I would eliminate the AST. I see it as just another failure point (more hoses), clutters up the engine bay, and it really doesn't do anything as long as you know how to get the air out of the system after replacing the coolant. We never really run them on builds unless a customer insists on one. Get a new oem .9 bar radiator cap. I'm not a fan of the higher pressure caps.

What the best way to cap/block off the lower center rad fitting? Piece of hose with a plug in it?

No just leave that alone. Run the hose from the ast delete filler body to the overflow. The hose right below that on the actual thermostat cover goes to the small nipple on the radiator. If you want to eliminate that it really should be welded. Caps/plugs fail over time.

Thanks Ihor. That was my bad, if I had gone out the garage to look first before posting I would have realized I was going to have another line to plumb and not need to plug anything.

sounds pretty straightforward to me...

if it holds 13psi and doesn't bypass the cap and push coolant into the overflow(faulty AST or AST cap) then the system is being overpressurized. a faulty coolant seal won't always allow coolant into the engine.

course if you want to verify that, common sense sais to install the tester onto the engine while running and see how high the pressure it builds is. the gurgling should have already given you the hint, it's not super complicated.

I guess an update of sorts. Removed the AST and the first short run seemed fine. The next night drove it longer and then things started to go south. Coolant buzzer came on so I headed straight home. Overflow tank was overflowing and there was coolant all along the bottom and side of the car. So a rebuild it is I guess. Sucks. The upside will be starting with a fresh rebuild that can handle future mods.

Hope to pull the motor in the next few weeks while I come up with a plan for the rebuild.