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Either the fan isnot pulling enough air through the radiator or the water pump is not moving enough coolant through the system. Not enough air through the radiatorwould explain why it heats up while sitting and then cools down when you drive. Check the fan and the fan clutch. Also check the radiator and the A/C condenser in front of the radiatorto make sure thatthey arenot stopped up with dirt or debris so that air can't get through.
The other possibility is that there is not enough coolant running through the system. I have seen water pumps that looked perfectly good, but the fins inside the pumphad corroded away and so there wasnot enoughleftto move the full amount of coolant.
Fan is spinning, and seems to pulling air pretty good. Coolant levels are good. I had them flushed before this past winter and changed. I also washed off the outside ofthe radiator and stuff before I had it flushed to make sure air was passing through.
It tends to also overheat when I am towing.
I guess I need to check the water pump. Anyway to test that without removing it?
Ron had some great recommendations.
The most common cause of overheating in the manner that you describe is a faulty fan clutch, even if it is bad it will still spin up fairly well and draw air threw but not enough to keep the engine cool at idle or when heavily loaded in the summer heat.
In the morning (before the engine has been run) pop the hood and spin the fan by hand, it should feel fairly tight and have some resistance and not freely spin around.
And on a 7 or 8 year old vehicle I would recommend replacing the radiator cap.
I replaced the fan clutch but the problem was still there. Talked to someone at a Car-X since the dealerships around here refused to answer any questions over the phone or make any suggestions. He said to check the temperatures of the radiator at the top, middle and bottom.
I used a temp gun, top was 190, middle 189, bottom 120. I replaced the radiator and works perfect now. Pulled my race car on Friday night, air on high, never got above normal operating temperature. Thanks for the help guys. Hopefully, this will help someone else in the future.
By the way, Autozone charges $250 - $350 for the radiator. Dealer - $550. I got one at Smyth Parts Plus in Cincinnati for $150. Just in case anyone else is in the area, they sell all radiators pretty cheap.
ive got a 2000 silverado 1500 4wd at an idle the engine is overheatingwith the ac on and normal with it off i was thinking fan clutch so i put a new one on still the same problem coolant level is good also any ideals how to fix this