Weird overheating...

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Jordan Gladman
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Weird overheating...

Post by Jordan Gladman »

I suspect a blown headgasket after a bad boost spike... heres what happening...

When I drive the car and boost the temp will start to rise all the way to hot and the heat inside will stop working, when I pull over the coolant resevoir is half full. I suspected that there was a small pinhole in the headgasket and compression was displacing coolant out of the cooling system. However, when the motor cools right off, it draws all the coolant back in, which would suggest air isnt being introduced to the cooling system. Also, when the car turns off it continues to overflow for about a minute which would also suggest a genuine overheat situation.

When I built the motor I put in a new OEM water pump, stant thermostat, OEM water temp sensor, OEM rad and rad cap. So the cooling system should be gold, not to mention its below freezing out. The car has been driving for 3 weeks now without problems til yesterday, so it should be good.

The only thing I noticed the motor doing before the boost spike that could be related was a high idle after the car warmed up. I've blead the cooling system a couple times and it doesnt solve this problem.

Does this sound like a bad thermostat?
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Post by Marcus »

Just my two cents jordan. It'd be a good idea to pressure test the system. I had an NA car that acted horrible like that. Turned out a hairline crack on a radiator is just enough to cause air pockets. Your theory is good I'm just adding food for thought. Perhaps something is bleeding off that pressure with rpms...not boost? Good luck buddy. :wink:
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Jordan Gladman
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Post by Jordan Gladman »

I was holding the revs pretty high with the car in my garage and I couldnt get it to overheat or to overflow. Within 3-4 min of driving with boost it was overflowing though.... ill see what I can rig up for a pressure test.
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Post by Marcus »

Jordan Gladman wrote:I was holding the revs pretty high with the car in my garage and I couldnt get it to overheat or to overflow. Within 3-4 min of driving with boost it was overflowing though.... ill see what I can rig up for a pressure test.
:cry:

Dang.
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Jordan Gladman
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Post by Jordan Gladman »

Coolant isnt getting into the cylinders at 15psi pressure. And after a short drive w/ a bit of overheating, the car cooled off and radiator was still topped off...

Im thinking it might be a thermostat issue. Im gonna trying pulling it out all together and see what happens, will update.
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Walperstyle
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Post by Walperstyle »

I would agree that its probably thermostat issue.

Any possibility the flow of your coolant is messed up somehow? How quick does your heater warm up the cabin?
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Post by 240tuned91 »

i had the same thing head gasket shortyly went out.

overheating + boost spike = fail im sure plenty of people on here can vouche.

i hit 28lbs on my td-06 20g. fixed that overheated hit 6 went air was all bled out and it was to late. headgasket took a shot
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Post by s13grady »

This is a really odd scenario here. Symptoms do suggest a possible headgasket issue but the fact that you pressurized the cooling system and it did not show any internal leaks rule that out. I noticed you only pressurized to 15 psi though. The first thing i would do is flush the system, make sure there is no blockage, check that thermostat and make sure its in properly (sounds like it could be backwards or blocked with sealer or malfunctioning, snowballing here).
If nothing changes after that, then it would be time to explore the other possibilities.
I hope it doesn't turn out to be anything too serious, keep us posted.
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Post by biggie »

Had this issue without boost on my old S13 (after water pump failure).

Would be perfectly fine until you ran it hard. Basically the HG is gone, but just enough to where under light load it won't leak and then under heavy load only pressurizes the coolant system (never any coolant leaking inward).
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Jordan Gladman
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Post by Jordan Gladman »

^Bingo.

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I spent almost an hour driving around trying to definitively figure out what it was. I rolled my car down the hill I live on and boosted a bit on a cold motor. I pulled over right away and there was definite pressure in the cooling system... so i thought, definately head gasket.. so i booted it home, boosted the whole way waiting for the temp to go up.. but nothing.. so I kept driving around, boosting/drifting for like 15 mins and nothing, wasnt even overflowing... I thought it was fixed... got on the highway for a second and did a pull through 3rd and 4th, sure enough.. over heating.

At this point I decided im pulling the head and sure enough, no4 cyl breach on headgasket. However, the hole was small and some gasket material was still there, so it was only bad enough to leak under high boost pressure. Makes it way harder to diagnose. So coolant doesnt necessarily have to leak into the cylinders when you have a blown gasket.

Either way, 2 hours to get the head off, should have it all back together and running tonight.
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