Overheated on track - now what?

[infernosg]

Overheated the car at Mid-Ohio during HPDE. 7th run of the weekend, 3rd of the day; ambient temperatures around 80F. Coming out of the esses (medium-speed, hard right turn, slightly uphill) in 3rd gear around 5000 RPM the low coolant buzzer went off and the temperature gauge started climbing. Let off and limped into the pits with the heater blasting but the gauge still got to "H". Spent no more than 5 minutes at that condition and did not exceed 3000 RPM during that time. Shut down and there was coolant boiling and steaming out of the overflow bottle. Once cooled off added water to the radiator - didn't take too much initially but the low coolant buzzer kept going off so kept bleeding the system and adding more water. Made the 2.5 hour drive home with no overheating issues but at lower speeds and/or tighter corners the low coolant buzzer would sound and then go off after a while. Added more water last night and drove the car to work today with no buzzer or overheating.

Some observations from before/after:
-Cooling system was flushed June 2010. 60/40 distilled water/anti-freeze mixture with a touch of Redline Water Wetter.
-Since Friday night there's been a high-pitched squealing only during low-speed deceleration. Sounds like belt squeal but goes away as soon as the clutch is pushed in or I get back on the gas. The "adjuster bolt" on the airpump sheared off so it is being held in place by the "lock bolt". Belt seems tight.
-Prior to the run was more coolant in the overflow bottle than usual.
-Prior to the run I had a hard time starting the car. Did the flooded engine start procedure and it limped to life with a little backfiring but idle was steady once warmed up.
-I changed my shifting plan that session - I only went into 4th at one point on the track, rather than three. Engine speeds were almost always above 5000 RPM, but never exceeding 7500 RPM.
-This morning it started a little harder than usual and the engine sounds a little "different" during decel. If in neutral and revved it almost sounds like a 'hissing" noise as engine speed drops but it goes away when it hits idle speed.
-No white smoke, no power loss or any other driveability issues that I can discern.

I know I need to flush and fill the system again - need to get the tap water out of there. Next will be an attempt to replace the sheared adjuster bolt in the airpump and then replace all the belts, but then what? Inspect/replace thermostat? Waterpump? Why did the low coolant buzzer keep coming on and going off? Most importantly, is the engine fried?

For the people who track their FC's is this a result of water pump cavitation? Time for an underdrive pulley of some sort? Time to upgrade the radiator?

[vex]

Originally Posted by infernosg

Overheated the car at Mid-Ohio during HPDE. 7th run of the weekend, 3rd of the day; ambient temperatures around 80F. Coming out of the esses (medium-speed, hard right turn, slightly uphill) in 3rd gear around 5000 RPM the low coolant buzzer went off and the temperature gauge started climbing. Let off and limped into the pits with the heater blasting but the gauge still got to "H". Spent no more than 5 minutes at that condition and did not exceed 3000 RPM during that time. Shut down and there was coolant boiling and steaming out of the overflow bottle. Once cooled off added water to the radiator - didn't take too much initially but the low coolant buzzer kept going off so kept bleeding the system and adding more water. Made the 2.5 hour drive home with no overheating issues but at lower speeds and/or tighter corners the low coolant buzzer would sound and then go off after a while. Added more water last night and drove the car to work today with no buzzer or overheating.

Some observations from before/after:
-Cooling system was flushed June 2010. 60/40 distilled water/anti-freeze mixture with a touch of Redline Water Wetter.
-Since Friday night there's been a high-pitched squealing only during low-speed deceleration. Sounds like belt squeal but goes away as soon as the clutch is pushed in or I get back on the gas. The "adjuster bolt" on the airpump sheared off so it is being held in place by the "lock bolt". Belt seems tight.
-Prior to the run was more coolant in the overflow bottle than usual.
-Prior to the run I had a hard time starting the car. Did the flooded engine start procedure and it limped to life with a little backfiring but idle was steady once warmed up.
-I changed my shifting plan that session - I only went into 4th at one point on the track, rather than three. Engine speeds were almost always above 5000 RPM, but never exceeding 7500 RPM.
-This morning it started a little harder than usual and the engine sounds a little "different" during decel. If in neutral and revved it almost sounds like a 'hissing" noise as engine speed drops but it goes away when it hits idle speed.
-No white smoke, no power loss or any other driveability issues that I can discern.

I know I need to flush and fill the system again - need to get the tap water out of there. Next will be an attempt to replace the sheared adjuster bolt in the airpump and then replace all the belts, but then what? Inspect/replace thermostat? Waterpump? Why did the low coolant buzzer keep coming on and going off? Most importantly, is the engine fried?

For the people who track their FC's is this a result of water pump cavitation? Time for an underdrive pulley of some sort? Time to upgrade the radiator?

I hate to say this, but it sounds quite similar to a soft seal letting go. You might want to let the engine sit for a day or two and check to see if you have any pooling coolant in the combustion chamber.

When mine let go I could easily start it up and run it around town, but as soon as it hit operating temperature the engine would start to run on one rotor. When temperatures got warmer the car got harder and harder to start.

Also pay attention to dropping coolant levels. You may have a link somewhere (whether it's by the water pump housing, a hose, or internal of the engine).

[infernosg]

Originally Posted by vex

I hate to say this, but it sounds quite similar to a soft seal letting go. You might want to let the engine sit for a day or two and check to see if you have any pooling coolant in the combustion chamber.

I assume I check this by pulling the EGI fuse and a spark plug and cranking the engine to see if anything comes out? Spark plugs are also something I need to check.

Originally Posted by vex

When mine let go I could easily start it up and run it around town, but as soon as it hit operating temperature the engine would start to run on one rotor. When temperatures got warmer the car got harder and harder to start.

I drove 2.5 hours back home yesterday at speed >70 mi/hr and I'm positive I didn't loose a rotor, or any power for that matter. If I do have a failed coolant o-ring or rotor housing, it must be very small. The weird thing about the hard starting is that it was easier to start it this morning (ambient temperatures ~65F) after sitting all night than it was yesterday afternoon (ambient temperatures ~80F) after only sitting for ~3 hours.

Originally Posted by vex

Also pay attention to dropping coolant levels. You may have a link somewhere (whether it's by the water pump housing, a hose, or internal of the engine).

I have no found any large external leaks, but that doesn't mean much. When I flush the system this weekend I'll get a much better idea of what kind of shape everything is in. As far as I know the radiator, cap and water pump are all original OEM equipment. I'm pretty sure the thermostat was replaced at some point and if it was I'm almost positive it is not an OEM part.

In the meantime I guess I'll just keep an eye out on the coolant level. The coolant level sensor seems overly sensitive to me, but it hasn't come back on in a while. If nothing changes I can only conclude the conditions simply outmatched the car's 22 year-old cooling system and some upgrades are in order.

Originally Posted by 88turboii

it was opposite for me when i had bad coolant seal. it would run on one rotor at start, but after about 15 seconds or so it would run like normal. white smoke on startup, from the coolant puddling in the chambers burning off. that and i could fill the overflow container with a couple 3rd gear pulls lol

Would the white coolant-smoke and smell make it past two catalytic converters? Aside from Magnecor spark plug wires and a K&N drop-in filter my engine is all stock. The exhaust was replaced after the manifold at some point but it looks to be a stock replacement, not a performance modification. I only ask because I see no smoke and don't smell coolant at the tailpipes.

Originally Posted by 88turboii

but yeah i also have overheating problems on the track. it will start creeping past 1/2 way after about 10 minutes of track time, even in cool weather. im still running a tmic, so the radiator should be getting plenty of flow. it was suggested to me to use aluminum tape and seal off all the parts around the radiator that air could get past, but i have not tried that yet

I was about 20 minutes into the session - literally the last lap before cool-down. As far as I know, this is the only time the gauge crept past 1/2 way during all of the sessions. When I heard the buzzer I looked at the gauge and it was just then starting to move from 1/2 way to "H" - it's not like I ran a full lap at WOT with the gauge pegged at "H".

[vex]

Originally Posted by infernosg

I assume I check this by pulling the EGI fuse and a spark plug and cranking the engine to see if anything comes out? Spark plugs are also something I need to check.

If you were closer I'd lend you my bore scope (makes checking things really easy). But yes, you can do it that way too.

I drove 2.5 hours back home yesterday at speed >70 mi/hr and I'm positive I didn't loose a rotor, or any power for that matter. If I do have a failed coolant o-ring or rotor housing, it must be very small. The weird thing about the hard starting is that it was easier to start it this morning (ambient temperatures ~65F) after sitting all night than it was yesterday afternoon (ambient temperatures ~80F) after only sitting for ~3 hours.

Which makes sense if you have a casting give way.

I have no found any large external leaks, but that doesn't mean much. When I flush the system this weekend I'll get a much better idea of what kind of shape everything is in. As far as I know the radiator, cap and water pump are all original OEM equipment. I'm pretty sure the thermostat was replaced at some point and if it was I'm almost positive it is not an OEM part.

In the meantime I guess I'll just keep an eye out on the coolant level. The coolant level sensor seems overly sensitive to me, but it hasn't come back on in a while. If nothing changes I can only conclude the conditions simply outmatched the car's 22 year-old cooling system and some upgrades are in order.

Sounds like a plan.

[RETed]

Originally Posted by infernosg

Spark plugs are also something I need to check.

This should tell you if the engine is bad or not.
No sense guessing everything else unless you get confirmation...


-Ted

[infernosg]

Originally Posted by RETed

This should tell you if the engine is bad or not.
No sense guessing everything else unless you get confirmation...


-Ted

When it stops raining this is my plan - I'll even post pictures when I'm done. I suppose with coolant/water I'm looking for a white/yellow fouled plug?

The car started and ran just fine after work yesterday. No buzzer, no overheating, no weird noise (other than loose belts). Letting is sit for today and I'll see what it does tomorrow morning (pending plugs).

Is it possible the slightly loose airpump belt was not providing enough friction on the water pump and it was slipping at higher RPM?

[RETed]

Originally Posted by infernosg

When it stops raining this is my plan - I'll even post pictures when I'm done. I suppose with coolant/water I'm looking for a white/yellow fouled plug?

Not necessarily...

Typically, if coolant is leaking into the chamber, the spark plug is going to come out clean - it's like if you're running water injection.
If you have the leading versus trailing plugs next to each other, it'll be obvious.


-Ted

[88turboii]

it was opposite for me when i had bad coolant seal. it would run on one rotor at start, but after about 15 seconds or so it would run like normal. white smoke on startup, from the coolant puddling in the chambers burning off. that and i could fill the overflow container with a couple 3rd gear pulls lol

but yeah i also have overheating problems on the track. it will start creeping past 1/2 way after about 10 minutes of track time, even in cool weather. im still running a tmic, so the radiator should be getting plenty of flow. it was suggested to me to use aluminum tape and seal off all the parts around the radiator that air could get past, but i have not tried that yet

[infernosg]

Well, the new radiator cap didn't seem to do anything. Somehow there is still a constant stream of air/gas going into the overflow bottle. Every now and then some water comes with it so pressure is being built up somewhere. Additionally, when I remove the radiator cap with the car running and warmed up it just keeps bubbling like the system never seems to be fully bled. If I add more water while it's running it seems to just want to push that and more out.

I have a new radiator, coolant hoses and water pump on the way (they are probably do to be replaced anyway) but I'm not thinking any of those are failed. Time to start pulling things apart now?

[vex]

Come to the car show...
Borrow tools...
?????????
Profit!

[infernosg]

Originally Posted by vex

Come to the car show...
Borrow tools...
?????????
Profit!

Something tells me a rebuild will take more than a weekend and besides, The Mitty > CCVT car show.

I'm going to try one more bleeding technique as suggested by the Haynes manual, which involves running without the radiator cap with the car cold. If that doesn't do anything then I guess it's time for a rebuild. I can't think of any other reason why I'm getting a constant stream of gases, occasionally accompanied with coolant, flowing into the overflow bottle other than a water jacket o-ring or housing failure.

Bottom line: is there any way this could be attributed to a bad thermostat or leaking radiator/water hoses? If not, like mentioned above, it looks like rebuild time.

[Pete_89T2]

Originally Posted by infernosg

Bottom line: is there any way this could be attributed to a bad thermostat or leaking radiator/water hoses? If not, like mentioned above, it looks like rebuild time.

Not the thermostat, since it's an internal part. But in theory, if water can leak out of an extrenal part exposed to air such as a hose or radiator, then air can get in too. But you tested the system with the pressure tester and it passed, most likely you would have found a leak. Only exception to that I can think of is since the pressure test is done under static conditions (engine not running, at whatever temperature it was at when you tested it), the test could miss a leak that only occurs under some combinations of dynamic conditions (i.e. temperature cycling, vibration, etc.).

[vex]

The only other possibility that I could think of would be that the water pump housing is starting to leak. Whether it's from the impeller or from mating surface would be difficult to say. It wouldn't have to be a large leak. When I did my rebuild that was an issue I had to overcome.

Other possibilities might be cracked coolant lines that run into the heater housing (let alone the heater might be leaking as well). Basically you'll need to track down to see if there's a pin hole leak anywhere in the car.

Or you could just shove a borescope (or a mirror) into the exhaust ports and see if there's any coolant pooling.

[infernosg]

Both valid points. What seems to be missing though is any sign of an external leak. I'm not seeing anything from any of the lines; nothing from the radiator and nothing coming out of the "weep hole" on the water pump housing. By "signs" I mean no leaking fluid, no evidence of dried fluid, no steam while running, no coolant smell, etc. Also, if there were a small leak allowing air into the system wouldn't that air just bleed off and stop at some point? The system is pressurized when the car is running so wouldn't that prevent additional air from entering?

I'm not sure if I'd say the pressure test "passed". I brought the system up to 15 psi and within 10-20 minutes it had dropped to 14 psi. You would think a perfect system would hold pressure indefinitely.

I still think I'm missing something about the bubbling in the overflow bottle. Something is causing a pressure build-up in excess of 0.9 bar but it's not a constant stream of fluid that's coming out like what would happen with an over-filled system. It's a mostly steady stream of gas, whether it be escaping air pockets (but they never stop), boiled fluid (possibly a result of a stuck thermostat) or exhaust gases I'm not sure. I suppose the only way to tell is to have the system checked for the presence of exhaust hydrocarbons but I don't know where I'd go for that.

I have a new thermostat that is not yet installed and a new radiator, water pump and full set of hoses on the way. Is there any hope that installing all those would rectify the issue? If not, I guess I'm just going to have to tear the engine apart.

[RETed]

Sorry to hear it's not going too well...

Have you tried to smell the coolant (bubbling)?
If it's combustion gases getting into the cooling system, the smell will give it away.
Normal coolant smell is a lot diffferent from combustion gases in the coolant.

There is a chance that you have a very tiny break in the water jacket o-ring on the combustion / exhaust cycle of the rotor housing.
The combustion pressures can hit around 1,000psi with the exhaust cycle pressures several times higher than the typical 15psi, and this would explain what you're experiencing.


-Ted