Cooling problems 2000 GMC 2500 5.7

T.Ogle · April 1, 2018

I hope someone can help me figure this out..I had a leaking water pump on my 2000 GMC Xtracab 3/4 ton truck, it never overheated and always stayed around 195/200 since I replaced the thermostat 2 months ago (PO had installed a 160 and was throwing the computer out of wack ) So I figured since I need this truck to work and be dependable I will just replace the entire cooling system, Bought all parts from RockAuto. AC Delco Waterpump, Larger Desert Radiator 2"core, Original was a 1", New Fan Clutch, New Belt, Idler pulleys and Tensioner, New hoses, Filled wit Dex Cool Coolant. I flushed the block with water pump off to get all the green coolant out, flushed the heater core. Put every thing together filled coolant and started it up..Now the darn thing want's to overheat..It got up to 215-220 and I shut it off before any damage happens..Coolant didn't seem to be circulating..I'm scratching my head here..can some help me out?

Doug_Scott · April 2, 2018

Very likely an air lock. Usually in the heater core. Sometimes you can simply disconnect one heater hose with the engine running(don't do it on a hot engine) to get the coolant to push the air out. Make sure you have the heater control set to hot.

Double check the fan is pulling air through the rad, not pushing. If it's pushing you have the belt routed properly and the water pump is also running backwards. You may want to verify you have the correct pump as well.

Not sure why you went with Dex cool, I would have switched to Evans Waterless coolant that does not expand when heated, never needs changing, and does not contain any corrosive properties.