5.3L engine overheat mystery

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Alicia P

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My 2001 yukon 5.3l had an issue with overheating and amongst several other things we noticed a constant air bubble problem in the coolant resevoir, needless to say we decided we needed to pull the heads. So we pulled the heads and had them worked, resurfaced and so forth. When we got the heads back we used new gaskets, all new bolts, new lifters, did the knock sensors while in the area, also put a new EGR, and all new exhaust bolts, and a new thermostat as well. After getting everything put back together and refilled with coolant, im still having the same issue as before the repair! Still trys to overheat and still has a steady flow of air bubbling out of the coolant resevior... I did a compression test on cylinders as well and all the compressions were fine. Any suggestions on what to do to fix my car? Ive already spent close to 1200 bucks and dont wanna keep throwing money...Thanks!
 

Tonyrodz

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I'd also check the condition of your radiator, what it looks like INSIDE of the radiator. I'm just spit balling here, but it's a good place to start.
 
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Alicia P

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I'd also check the condition of your radiator, what it looks like INSIDE of the radiator. I'm just spit balling here, but it's a good place to start.

Has a fairly new radiator, probably put it on within the last 4 or 5 months. But ill look into it.
 

swathdiver

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You may have a cracked cylinder head. Did the shop magnaflux them to check for cracks? The other tests are a pressure test of the cooling system and a leakdown test of the motor, more advanced than a compression test. Do those two and the problem area will be revealed.
 

SnowDrifter

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You may have a cracked cylinder head. Did the shop magnaflux them to check for cracks? The other tests are a pressure test of the cooling system and a leakdown test of the motor, more advanced than a compression test. Do those two and the problem area will be revealed.
Since OP has it together and running, a block tester is I think the easiest course of action. It's just a bubbler with some fluid in it that changes color in the presence of a high CO2 concentration e.g. combustion gas in the coolant

https://www.autozone.com/loan-a-tools/loaner-block-tester
 

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