wojo1973

Truck would run warm intermittently. I borrowed a co worker's pressure tester and I found a crack in the left tank of the radiator on my 1998 C1500 5.7 L. When I replaced the radiator (Same dimensions and core thickness as OE), since the following had not been replaced since I bought the truck in 2003 I also replaced Water Pump, Thermostat, Fan clutch, Upper and lower hoses, by pass hose, & belt. Now the temperature rises to above 230º (According to Gauge & Friend's OBDII Scan tool) in about 10 minutes. After letting sit and cool off Took out on Highway at 60 mph and still runs about same temp. Let it cool down; took thermostat out and removed top hose at radiator (thinking might have air lock in engine block cooling passages). Coolant comes out at about half stream when engine revved up. Put hose back on radiator and ran truck without thermostat at idle about 10 minutes. Got up to 115º. On highway gets up to about 150º without thermostat. Changed thermostat with another new one. Overheating problem back.Before I replaced all the parts the engine ran below 200º except when the coolant low because of coolant loss from the crack in the tank. (Frustrated: I used to work as a mechanic and never had as much trouble with a vehicle as this) Can anyone tell me how to troubleshoot and narrow down which part is not doing its job?

Richardx2

You probably have some air trapped in the engine. When the thermostat is closed it will not allow the air to escape and when you are operating the engine with the radiator cap on the air has nowhere to go. Also look at the level of the upper radiator hose to make sure it is not higher than the top of the radiator. If the hose is above the top of the radiator then the water pump is trying to push the coolant uphill.

Try "burping" the coolant system. You can find a few vids on youtube that explain the process. I also drill a 1/8" hole in the thermostat that allows the air to escape. Had the same issue when I replaced my heater core, drilling the hole in the thermostat fixed the issue.