Overheating problem

Max Technician Glendora, California Posted   Latest  
Question
Driveability
2017 GMC Sierra 2500 HD 6.6L (Y L5P) 6-spd (1000)
Vehicle Overheating

Hello Everyone, I have this 2500 l5P 6.6l it came in for overheating problem. Customer said they started noticing the temp Gauge reading higher then normal just yesterday but it would drop down as they were driving but then the low coolant light came on he added a gallon of coolant and drove it here. There is no sign of coolant leaking anywhere on the engine. this one has the expansion tank with 2 caps. I started the truck dead cold to check proper level and within just 4 minutes of the engine running the upper radiator hose was hard remove the expansion tank cap and it was already full of pressure coolant temperature was not even 80 degrees. If I leave the truck running the heater will get hot and the temperature never when over 179 degrees and coolant just started to overflow. im incline to think i have possibly a head gasket problem because it has pressure as soon is i started cold but i dont wanna discard the idea of maybe a bad egr cooler. I'm not to familiar with problem on this newer engine. 

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Travis Technician
East Montpelier, Vermont
Travis Default
 

Have seen a couple L5P trucks with head gasket failure, same symptoms.

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Marlin Technician
Estacada, Oregon
Marlin Default
 

If coolant pressure exceeds exhaust pressure, the EGR cooler is not the problem. This is very easily tested with a pressure tester on the degas bottle. Exhaust pressure is very low, only a few PSI, at warm idle, unless the is an turbo or exhaust system fault, and can be monitored via a scan tool.

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Randy Diagnostician
Glendora, California
Randy Default
 

Put your coolant pressure checker on it . And start up and run if pressure comes up fast it is a head gasket

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Philip Educator
Hemet, California
Philip Default
 

Sounds exactly like my LB7 with leaky, multi-layer steel head gaskets. Never overheated as long as I kept coolant in it. Just would blow the coolant out and the radiator hose would get hard like that very quickly. How many miles on this vehicle, incidentally? I'm interested to know if the L5P is having low miles head gasket issues.

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Max Technician
Glendora, California
Max Default
 

125 000

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Vinney Owner/Technician
Congers, New York
Vinney Default
 

If you have a emission gas tester you can check for emission gasses in the bottle

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Max Technician
Glendora, California
Max Default
   

I was not able to get gases reading with the emissions machine but the block tester after it run for a few minutes hot it defiantly shows bad. It built up to 20 psi in the coolant system before it reached 120 degrees.

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Randy Diagnostician
Glendora, California
Randy Default
 

Yep pressure shows head gasket . Very easy test

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Caleb Diagnostician
Mishawaka, Indiana
Caleb Default
 

You could pressure test the EGR cooler/coolers on the bench. Does it have a water too air intercooler? If so this could push boost into the cooling system. Otherwise sounds like you have a classic head gasket problem.

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