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Discussion Starter · #1 ·
I just purchased an 02 Duramax (190,000) miles and had the engine checked because I noticed low coolant and lack of heat when idling. The Chevy dealer ran all of the usual tests (compression, die, exhaust, oil consistency, etc. ) and nothing indicated head gasket leak. However, I do seem to be getting air into the radiator system causing escape of coolant through reservoir. Also, I lose (cabin) heat when truck idles, and upper radiator hose seems to hold pressure even after truck has been sitting overnight. Otherwise, truck seems to run good. Just drove 400 miles, maintained 207 degrees engine temp, and purred along at 70 mph at about 2000 RPM. No indication of heating up. Could this be anything OTHER than a head gasket problem? Where else might air be coming from? I checked my radiator system this morning after truck was sitting out in cold all night following trip home (400 miles). The top radiator house was somewhat squeezable. It wasn't collapsible, but it wasn't rock hard either. Upon unscrewing the coolant reservoir cap and releasing some air pressure (did not seem to be a lot there) the upper radiator hose was then very easy to squeeze closed with my hand. My coolant level in my reservoir (though the truck is on a slight driveway grade) appears to be down about 2 inches below the FULL mark. I'm still not getting much heat while truck's idling in driveway (15 minutes) -- I suspect because I have air pocket in radiator system. Where might air be coming from?

Thanks -
 

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You'd be very surprised to know that a dirty coolant tank cap can cause this,also on the upper therm housing,there is a 12mm nut,that is the proper way to bleed the air from cooling system...good luck!!:drink
 

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Discussion Starter · #3 ·
Is it at all likely/possible that the Chevy dealerships diesel/duramax mechanic actually missed something as simple as this? He spent an hour running tests only to find that all of his tests were "inconclusive". He seemed earnest and knowledgeable. He said he bled an extensive amount of air out of the system and put in 3 gallons of coolant. (I later learned that one of the guys who prepped the truck for me prior to my buying it had opened the reservoir under pressure and dumped coolant all over himself. So that explains where that coolant went (the Chevy mechanic did not have this bit of information). Anyway, upon bleeding the air and refilling he tested the truck on the rack at sustained, high RPMs and found no further problems (heater worked OK). -- Unfortunately, I'm still experiencing air build-up in the system. Still think it might be as simple as a dirty coolant tank cap or problems compounded by incorrectly venting (reservoir cap) air from system? Other sources of air building up? Heater core issues?
 

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Probably wouldn't hurt to just flush system good, put in new thermostats and cooler cap and burp air out good. Seems to me if you have air, then only half burp it out, seal it up and drive it that the air pockets work up again and recause the same problems. As said above, USE the BURP HOLE, it works. If it takes you 10 times using it to get all the air out, so be it. Some will get it out in one or two times, some 10. Just all depends. Also, did they use a chemical (blue maybe? Not talking about the "dye") at the overflow cap (don't recall what it is called off hand- but it changes colors in the vial if there is a slight head gasket leak. Seen it work twice where other "common problems" didn't diagnose it correctly, and sure enough it was the head gasket out in both cases. Worth a shot maybe trying this first before you flush system out too.
 

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Discussion Starter · #5 ·
Head gasket leak test you described was negative. Tech said it's accurate 90% of the time and therefore, while not positive for a leak he can't absolutely rule it out. It sounds like we're at a point where it's best to try the inexpensive things (caps t-stats) first.
 

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K, just didn't see it listed and wanted to make sure that all bases were covered for you...... I would start there then (flush, cap, therms). Again, BLEED, BLEED, BLEED!!!!!!!! (the air that is....lol)
 

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^^^^^^^^^^^
 

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Head gasket leak test you described was negative. Tech said it's accurate 90% of the time and therefore, while not positive for a leak he can't absolutely rule it out. It sounds like we're at a point where it's best to try the inexpensive things (caps t-stats) first.
The cap is cheap, $5. Then, The dealer tried the T-stats, that worked for about a week and then back to the same, coolant exiting the tank and the heater not working because the engine temp delays in rising.

The tech pulled the glow plugs and then rotated each cylinder to test with pressure there. When he found the problem cylinder, air bubbles appeared in the tank.
 

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Discussion Starter · #9 ·
Forgive my ignorance.... what was required to fix the problem once he found the problem cylinder? (Head gasket?)
 

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The test confirmed a leak, either from the HG or damaged head. Removal of the head is then neccessary to determine which it is, and also to see which one of 3 different gaskets is used.
 

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In my case, a piece of gasket fell into the cylinder and scored the walls and piston....New warranty motor installed.

Did this happen early on, or after continuing to drive and nurse it, waiting for an opening at a Dealer to get in. Who knows. :idkidk
 

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lyle, did you ever find your problem?
 
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