I have a '73 Chevy C-10 with a 350. It is getting hot at interstate speeds but cools down in traffic. I have electric fans, that are pulling the right direction, had radiator checked and cleaned, new water pump, thermostat, hoses, and timing set right. Please help.
How was the radiator cleaned? If you mean flushing water through it, that doesn’t remove any solder bloom that has formed in the radiator cores which reduces the radiators ability to flow coolant. If this is the original radiator, it’s thirtysix years old. And it would come as no surprise that a partially restricted radiator is causing the overheating issue at highway speed.
Have you considered a leaking head gasket?
Took it to a radiator shop.
Truck runs fine, don’t seem to get any indications that I would have one. It runs perfect without smoke, water in the oil, or any of the usual signs.
Run the truck until it overheats, pull over and look in the top of the coolant reservoir (engine idling). If you see small bubbles rising through the coolant, you have a head gasket leak.
The addition of electric fans tells me you have been taking some “extreme” measures to solve this problem.
I had a 65 GMC with a pumped up small block and it could idle 12hrs straight without overheating. I had a 4 core radiator,no shroud,headers,and the AZ desert heat to contend with.I used the truck for hauling a 3 yrd dump trailer and I would work the whole day withot shutting it off.
Well I should say that it doesn’t “overheat”. It gets hotter than normal according to the temp gauge. I have also thought about changing out the temp sending unit and possibly the gauge. Not sure how old the sending unit is, but I know the gauge is 36.