Ok im stumped
 

Have a friend with an '02 chevy 3/4 ton 6.0 CNG/Gas and it is having a overheating problem on long distance hauls. He changed the water pump, thermostat and flushed the system a couple times and it still does it. He brought it over for me to look at and i went and drove about 5 miles down the hwy and it runs great and temp is right at 200 until you hammer down on it and it jumps to 220 and if you do it again approx 80 mph it slowly climbs towards 260. It didnt seem like it was getting warm to me at first and i replaced the sensor and washed through the coils on the radiator and condenser and it still does it.. head gasket maybe?? Any ideas??

Thanks

Re: Ok im stumped
 

Clogged radiator? Classic symptoms when getting hot a high speeds, Does it cool down when you slow down?

Re: Ok im stumped
 

Not fast but yes temp does drop a bit.
take cap of before it warms and its normal like every other truck, kind of see it flowing and both upper and lower radiator hoses feel the same temp but my thermo infared gauge at work so I can't tell exactly.
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Re: Ok im stumped
 

we had an 03 zr-2 s-10 that would only over heat at highway speeds or pulling a tailier it was the radiator, we installed an after market rad on it and it over heated ever since installed a new dephi radiator and it hasn't over heated anymore

Re: Ok im stumped
 

Ok ill try that and see, thanks