Possible Head Gasket Blown?? - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 8 (permalink) Old 09-17-2012, 09:57 AM Thread Starter
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Possible Head Gasket Blown??

I'll start with about week ago I hit a Large porcupine. I was on my way to work and after hitting it I drove approx, 15 miles. I was stopped at a light and my coolant temp light came on. So i pulled away from the light while scrolling through to get temp. when I got it it was like 308 so I pulled over and shut it down. The next day I towed it home and replaced the radiator and ran it and everything seemed great. Temp ran about 188-194, I drove it to work 80 miles round trip all week. My wife takes the car to put gas in it (4 miles away) and when she started it after fueling it ran rough and she said it let out a cloud of white smoke out of the exhaust. she then shut it off and restarted it and it ran really rough for about a mile where she brought it to the garage. They took it for a test drive and returned with a temp of 204 but it ran good. after taking it into the shop the mechanic said the coolant system is building pressure and the head gasket is blown. My wife then drove the car home. I have since been driving it around a little to try and replicate the white smoke but I have not seen it happen yet, car seems to run fine with no power issues. there is no water in the oil and the coolant levels seems to be steady. I havnt drove it that much however, say 20 miles or so. The temp is fluctuating higher however than previously after changing out radiator. it gets to about 204-206 then goes back down to 190 ish and will fluctuate back and fourth. I shut it off and didnt use it for about a day or so and took off the coolant resevoir cap and it hissed out pressure. So after all that, would you consider what the mechanic said and that the gasket is blown?? i figure if the cooling system is buoilding pressure while running and the engine is warm and metals are expanded, shouldnt the pressure leak off when the engine is all cooled down?

Thanks for any advise or info you can provide.
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post #2 of 8 (permalink) Old 09-17-2012, 11:13 AM
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Have you noticed any rough starts since that day? Normal operating temp is 190-214 so you aren't outside of the norm. temp-wise. You would know pretty quick if the gasket was blown, there should also be a milky film on the bottom of your oil cap.

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post #3 of 8 (permalink) Old 09-17-2012, 12:05 PM
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Hey there glassmkr31,

Killing porqupines, huh? ;) Glad that everybody's okay - I know that when animals meet cars it can become a tricky situation.

I can check with our Technical Assistance Center on the normal coolant temperature for you if I could please get the last 8 digits of your VIN. Also, I noticed that you worked with a mechanic - was this through a GM dealership? If so, I'm happy to follow up on your visit with them.

You can either private message me here or send me an email at [email protected] (include "Attn: Sarah" in the subject line).

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post #4 of 8 (permalink) Old 09-17-2012, 02:23 PM
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Did you get any misfire codes? That is a sign of a blown gasket. Your temperature readings look normal and you're probably paying more attention to it. Keep an eye on the coolant and check the oil regularly for the next few weeks. If any of the two turns milky or levels change then think about gaskets. Your wife's incident might have nothing to do with the porcupine. Example; it could have been the purge solenoid and it flooded a bit upon fill-up. Keep an eye on it. Overheating an engine is never good but it doesn't always cause damage to the motor.

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post #5 of 8 (permalink) Old 09-17-2012, 04:10 PM
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i would say if it hit 308 temp. the gasket is done or the head is cracked
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post #6 of 8 (permalink) Old 09-18-2012, 12:31 AM
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I say check all your hoses and make sure they are connected all the way, and that there are no punctures.

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post #7 of 8 (permalink) Old 09-18-2012, 12:34 AM
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I mean if pressure keep building a hose could POP off.

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post #8 of 8 (permalink) Old 09-18-2012, 05:22 AM
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My dads diesel would hold pressure for days because his head gaskets were bad. Sounds like your car so its probably the gasket

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