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Old 10-08-2012, 06:37 PM   #1
STiSomeday
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Default Lifted head(s) that re-seated? Cooling system issues *UPDATE*

Car: 2005 STi, Cobb stage 2 93 octane, 81,000 miles. The only thing not stock about my cooling system is the hoses running up to the upper tank that Cobb supplies with the SF intake system. Coolant was flushed at 60K miles and again at 75K. 50/50 mix of clean, pure water and Subaru genuine full strength coolant.

I took the car on a ~500 mile drive yesterday on some awesome roads, I did a lot of high engine load driving (not high speed, just high RPM's/staying in the "power band" of 2nd, 3rd and into 4th. When we got the the end of the first leg of our route, my car smelled like coolant so I checked it out and saw that the overflow bottle was overflowing. I thought nothing of it because I figured it would get sucked back into the radiator, it gets full from time to time but the level always goes back down. We take an easy drive up to the next portion of our route (about a 30 minute break from running the car hard) and I start getting on the car again. Everything is normal but I notice the temp gauge starting to fluctuate. I turned the heat on and it didn't really make a difference so I pulled off on the first safe spot I could find to see the coolant overflow bottle was still at the top and overflowing slightly.

Sounds like I'm lifting the head(s) and combustion gasses are pushing the coolant out of the engine, right? I've seen the threads on here and on the other forums, it all seems to match up (no bubbles in my overflow bottle though?)

I took both caps off (the system was holding pressure, I had to use a towel and very carefully let the radiator vent before I could take the cap off). I added about 3/4 of a gallon of water, let the car run so the system would burp the air out, got back to the highway, checked the levels again and everything was fine. I then proceeded to drive 175 miles home with zero issues whatsoever. Temp gauge sat right above the first line like it always does, motor still pulls hard, no misfires, oil is clean and clear or any signs of coolant, coolant level is stable, the heat works, and the overflow isn't overfilling anymore.

If the HG was blown, it wouldn't just get better. I would think if I stretched the head bolts and lifted the heads it would still be showing signs of that as well? I'm at a loss here. I work at an auto parts store (not your typical store, the guys I work with and myself actually work on cars and know how to solve problems rather than stare at a computer) and one of the guys suggested that I may have boiled coolant, which would pressurize the system and force coolant out. It makes sense in theory but I don't know if this is possible or not. One of the other guys said I may have lifted the head and then it re-seated, but that doesn't sound right.

I just don't understand how I can be pushing coolant out of the system/overheating and an hour later drive 3 hours home on the highway at varying speeds and RPMs with absolutely no problem. I don't ever drive the car hard and the first time I do it does this. Maybe my constant "babying" of the car is the problem? I'm picking up a cooling system pressure tester and I'm going to send some oil out for analysis to see if there's any traces of coolant chemicals in it, but if anyone has any ideas or suggestions on other things to check out I'd really appreciate it.

*Update*

I think I may have found the problem. If I did, it was an incredibly easy fix, but I'll also kick myself for making such a dumb mistake. Hopefully it truly is this simple though.

I was looking at my dad's Saab 92-x Aero, as he thinks he has a cooling system leak as well. I was looking at his radiator to make sure the cap was the same as mine so I could use the same adapter on it when I realized his caps were installed reverse of what mine are. I then proceed to Google search "STi engine bay" and lo and behold my caps are on bass-ackwards. The 1.1bar cap is on my radiator and the 1.3bar cap is on my upper tank. Best part of that? They've been like that since I flushed the coolant on July 6th, 2011 (checked my service records to see when I did it).

So follow me on this one: With the lower pressure cap on the radiator, it would vent coolant out to the overflow sooner. The boiling point of the coolant in the radiator would also effectively be lowered, as I understand it, because higher pressure raises the boiling point. Assuming that coolant was venting too quickly from the radiator and its boiling point was reduced, I could have boiled coolant in the system which would have pressurized it. This would explain why the system was still pressurized when I removed the caps after it started overheating. It would also explain why the car was perfectly fine after I refilled the radiator and drove it home like I normally would drive it, and shows no other sign of head/gasket failure or damage.

Again, let me reiterate that I do not drive my car hard on a daily basis, so the coolant probably never got hot enough to cause this issue before, even though the caps have been switched for over a year now. If you guys knew how I normally drove my car you'd take it away from me and tell me I don't deserve it because I'm forcing it to live a sad, miserable life. I drive my 93 Impreza L 100x harder than I drive my STi, mostly because you have to drive it hard to get it to go anywhere, but also because I'm not worried about anything happening to it.

Anyhow, I'm still going to look into some of the easy things to check that you all have suggested and take the car out to try to replicate the issue, but I think I may have already found it.

What do you all think?
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Last edited by STiSomeday; 10-09-2012 at 07:10 PM.
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Old 10-09-2012, 03:21 AM   #2
UK-Wagon
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Change thermostat, and both radiator caps. The car is 7 years old, time to replace those. If the HGs lifted you wouldnt have made it home, period!
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Old 10-09-2012, 06:59 AM   #3
fastblueufo
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Default

Quote:
Originally Posted by UK-Wagon View Post
Change thermostat, and both radiator caps. The car is 7 years old, time to replace those. If the HGs lifted you wouldnt have made it home, period!
True this. I just lifted one and was spitting coolant out the exhaust after fixing a coolant hose that popped with 25 psi boost pressure going into the coolant system
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Old 10-09-2012, 11:01 AM   #4
STiSomeday
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Quote:
Originally Posted by UK-Wagon View Post
Change thermostat, and both radiator caps. The car is 7 years old, time to replace those. If the HGs lifted you wouldnt have made it home, period!
Quote:
Originally Posted by fastblueufo View Post
True this. I just lifted one and was spitting coolant out the exhaust after fixing a coolant hose that popped with 25 psi boost pressure going into the coolant system
That's what I was thinking. When I got home I did some research on what could cause the problem I was having and I saw quite a few threads pointing towards lifting heads, but that's not something that would happen and just go away.

I'm definitely going to replace the thermostat and both caps, I'm also thinking of flushing the cooling system again and making sure that none of the small hoses and lines are clogged. I wish there was a more "scientific" way to check to see when the problem starts happening rather than taking the car out and running the piss out of it, but I don't have access to an AWD dyno or anything like that so I'm stuck with what roads.

I suppose it is possible that I over-taxed my cooling system and boiled coolant. We were on these roads for at least an hour at a time and we might have averaged 30-35MPH. Basically it was WOT in 2nd or 3rd, on to the brakes, into a corner, and repeat. Maybe there wasn't enough air moving though the radiator to keep things cool and the coolant boiled, then with the pressure in the system from that it forced coolant out making the problem worse. It sounds exactly like what I've read about lifts heads on these cars to me though. I never over-revved the car but it was between 3000 and 6800 RPMs basically the whole time. I'm almost positive that both fans are working (I know they both kick on if I turn the a/c on) but maybe a relay was acting up and the fans weren't working properly either or something.
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Old 10-09-2012, 11:17 AM   #5
fastblueufo
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Is your car tuned correctly. At higher altitude it can cause the ecu to see lower loads which results in higher timing. If the tune is off or your cooling system isn't exactly up to par, the higher timing will tax the cooling system even more, on top of the already stress on the cooling system from the spirited driving.
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Old 10-09-2012, 12:55 PM   #6
STiSomeday
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Quote:
Originally Posted by fastblueufo View Post
Is your car tuned correctly. At higher altitude it can cause the ecu to see lower loads which results in higher timing. If the tune is off or your cooling system isn't exactly up to par, the higher timing will tax the cooling system even more, on top of the already stress on the cooling system from the spirited driving.
Tune is Cobb's standard off-the-shelf stage 2, 93 octane tune. We went through some altitude changes for sure but it wasn't anything drastic like being tuned at sea level and running through mountain passes. I wish I had some logs to look at but I didn't have my accessport plugged in.
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Old 10-09-2012, 07:10 PM   #7
STiSomeday
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Default

*Update*

I think I may have found the problem. If I did, it was an incredibly easy fix, but I'll also kick myself for making such a dumb mistake. Hopefully it truly is this simple though.

I was looking at my dad's Saab 92-x Aero, as he thinks he has a cooling system leak as well. I was looking at his radiator to make sure the cap was the same as mine so I could use the same adapter on it when I realized his caps were installed reverse of what mine are. I then proceed to Google search "STi engine bay" and lo and behold my caps are on bass-ackwards. The 1.1bar cap is on my radiator and the 1.3bar cap is on my upper tank. Best part of that? They've been like that since I flushed the coolant on July 6th, 2011 (checked my service records to see when I did it).

So follow me on this one: With the lower pressure cap on the radiator, it would vent coolant out to the overflow sooner. The boiling point of the coolant in the radiator would also effectively be lowered, as I understand it, because higher pressure raises the boiling point. Assuming that coolant was venting too quickly from the radiator and its boiling point was reduced, I could have boiled coolant in the system which would have re-pressurized it. This would explain why the system was still pressurized when I removed the caps after it started overheating. It would also explain why the car was perfectly fine after I refilled the radiator and drove it home like I normally would drive it, and shows no other sign of head/gasket failure or damage.

Again, let me reiterate that I do not drive my car hard on a daily basis, so the coolant probably never got hot enough to cause this issue before, even though the caps have been switched for over a year now. If you guys knew how I normally drove my car you'd take it away from me and tell me I don't deserve it because I'm forcing it to live a sad, miserable life. I drive my 93 Impreza L 100x harder than I drive my STi, mostly because you have to drive it hard to get it to go anywhere, but also because I'm not worried about anything happening to it.

Anyhow, I'm still going to look into some of the easy things to check that you all have suggested and take the car out to try to replicate the issue, but I think I may have already found it.

What do you all think?

Last edited by STiSomeday; 10-09-2012 at 07:16 PM.
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Old 10-09-2012, 07:46 PM   #8
BlueSTI4Me
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Can I kick you? (got2boostit2 from that other site)


Good find - need to note that in all the coolant leak threads -
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Old 10-09-2012, 07:54 PM   #9
STiSomeday
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Quote:
Originally Posted by BlueSTI4Me View Post
Can I kick you? (got2boostit2 from that other site)


Good find - need to note that in all the coolant leak threads -
I've already kicked myself but if you want to join in I deserve it
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Old 10-10-2012, 12:19 AM   #10
UK-Wagon
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Gahhhh WTF mate! You gotta know these things..... I thought about asking this but figured they were correct as that is something easily checked since it has it printed on the cap.

Nice fail OP, nice fail..... lol
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Old 10-10-2012, 05:20 PM   #11
STiSomeday
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2002 PSM WRX - DD

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The thought never crossed my mind as the last time I had the caps off was over a year ago. I just never drove the car hard enough for it to matter until the other day, haha. Thanks for all the help and suggestions everyone.
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