'01 chevy Z71 overheating

[Pappagimp]

I have an '01 Z71 that when you are just setting with the A/C on will overheat. If you turn the A/C off put it in neutral and rev up the rpm's the temperature will drop back to normal almost immedeatly. Could this be a problem with the A/C or just something minor like the thermostat sticking? I have had a 99 and now an 06 that will run all day and never try to heat up. Just looking for suggestions

[MLCinNCTX]

Might check you fan clutch and see if it is slipping. Turning the AC off removes a lot of heat load from in fron of the radiator.

You mentioned sitting still, does the truck stay cool while you are running down the road? If so, I think the fan clutch is bad.

[Flynm]

either your fan clutch or your water pump is going south.

[Dani California]

Check the water. If you are low put water in it. The problem should go away. If it goes away for a very long time and then comes back again low on water then you very possibly have an intake manifold gasket leak. On the 350 vortec this happened on mine and the leak was way back behind the engine on the top and you couldn't see it. It leaked so slow that if i would have put water in it when it got warm it would have went away for a long time. Intake manifold gasket cured mine. From what you describe it could JJJUUUUSt be getting low on water.

Biggie:biggrin:

[Pappagimp]

Might check you fan clutch and see if it is slipping. Turning the AC off removes a lot of heat load from in fron of the radiator.

You mentioned sitting still, does the truck stay cool while you are running down the road? If so, I think the fan clutch is bad.
yes it stays cool going down the road. However I have already put a new fan clutch on.

[FISHGUTS]

thermostat

[Roby]

If the thermostat is bad it will overheat going down the road as well. The water pump will not make engine overheat unless it is allowing the fluid to leak out. The fan clutch is the most likely culprit but you say this has been replaced. As mentioned earlier, be sure the coolant resevoir is full of coolant. Check for debris that could be blocking air flow through the radiator. You need to check between the a/c condensor and radiator as well as in front of the condensor. It is very important that you have unrestricted air flow across the radiator. If all these items check out, you have a radiator that is clogged internally. The tubes that run horizontally across the radiator can become restricted and coolant will not flow through them as well. I have seen where the bottom portion of the radiator becomes internally clogged from sediment that settles to the bottom of the radiator. If this is the case you will need to replace the radiator. The aluminum radiators are not worth repairing.

[MLCinNCTX]

If the thermostat is bad it will overheat going down the road as well. The water pump will not make engine overheat unless it is allowing the fluid to leak out. The fan clutch is the most likely culprit but you say this has been replaced. As mentioned earlier, be sure the coolant resevoir is full of coolant. Check for debris that could be blocking air flow through the radiator. You need to check between the a/c condensor and radiator as well as in front of the condensor. It is very important that you have unrestricted air flow across the radiator. If all these items check out, you have a radiator that is clogged internally. The tubes that run horizontally across the radiator can become restricted and coolant will not flow through them as well. I have seen where the bottom portion of the radiator becomes internally clogged from sediment that settles to the bottom of the radiator. If this is the case you will need to replace the radiator. The aluminum radiators are not worth repairing.Good call, a buddy of mine came over to the shop this weekend and mentioned his truck getting hot while sitting still with AC on. We checked the clutch and it appeared to be good, them check the radiator and AC condenser for blockage and spent the next 40 minutes blowing seeds, bugs, bird feathers, and othe misc. **** out of it. His truck is a 2001 Silverado CC 4wd and Chevy did not make it easy to work around the radiator. I have a radiator air wand that I use on my tractors and that was a big help. The radiator wand blows air out at 90* to the wand through a set of holes in the wand.

Also on the new clutch, was it a new or rebuilt clutch. It would be worth checking it to make sure it is working.