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Overheating Mystery

1K views 6 replies 5 participants last post by  A496HD 
#1 Ā·
New guy here. 2003 Silverado 2500 HD 6.0l 4x4. Having spontaneous overheating 230-240 troubles. Some days no problem other days overheating at idle. Started with radiator flush & fill (properly) not just add new fluid. Then noticed some "squishy" hoses which were replaced. Water pump & thermostat were just done about 6-8 months ago, but I removed the thermo, boiled it, all good. Still same trouble of random jump to 230-240. Noticed the fan clutch maybe not properly engaging, swapped it out...still no joy. Then I noticed at start up a bubbling sound coming from the heater core under the dash (which was also replaced last summer 2014), so I thought maybe I have an air pocket trapped in the cooling system. Since there is no bleeder on the system, I did another flush & fill and this time left the reservoir cap off till the thermo kicked open and a lot of bubbling came out but then 20 minutes into the test drive......you guessed it, overheating. I don't think its a head gasket issue cause the oil dipstick is nice shiny oil & I'm not losing coolant. Any other suggestions fellas??? Something I missed?? The only other swap I can think of is the radiator, but it doesn't appear clogged & all the fins look good. Thanks......
 
#2 Ā·
You don't say how many miles is on it but with all the other parts you have changed, the radiator is about all that is left. You cannot tell if you have a plugged up radiator by looking at the outside. If it is the radiator, it should over heat all the time. I would take it to a radiator shop and have a pressure test done on it.

Keep us updated on your findings.

Cf
 
#3 Ā·
Hmm. The mention of a bubbling sound makes my mind go to a job I did where the head gasket failed. I would have it pressure tested and make sure either you or whoever does it starts the truck and let's it run a little bit while they are doing the pressure test.

If the gauge is boucing around a lot or starts climbing then I'd say for sure your head gasket(s) are shot.

Hopefully it's something less major though.
 
#4 Ā·
Maybe check to see if you have any smoke coming out of the exhaust as well, particularly when it starts overheating. If the head gaskets are shot and there is coolant leaking into the cylinders, you should see some whitish smoke.
 
#6 Ā·
Gentlemen, I swapped out the radiator today, after ordering an all aluminum one that I found a great deal on, and waalah, problem solved. Upon removal of the old one, I discovered two problems, 1 was a bunch of smashed fins on the front side that I could see until removal and 2 both the plastic reservoirs for the oil & trans cooler lines had micro cracks in them with coolant leaking down the front. Thanks for all the great advice & glad I found this forum
 
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