2002 Cadillac Deville Running Hot

There are a few things that could cause overheating, here are some things that might help, the cooling system should be chekced with the engine cold after sitting for a while.

• First thing you might want to do is check the coolant in the reservoir tank, it should be at the proper full level.
• Sometimes when you change a thermostat there's a possibility you could get air in your coolant lines from having the coolant system opened up, this could keep your coolant from circulating through your system, if so you would need to bleed the air out of the coolant system.
• The water pump should be inspected for leaking coolant out of the weep hole's, when a water pump go'es bad it may leak coolant, which would mean the seals on the pump are bad, also listen for squeeling noise's coming from the pump when the car is started, if it squeels the bearings are bad, there is also a possibility the water pump fins are wore down from corrosion, there is no way to inspect this without removing the pump.
• check the drive belt for wear and tension, a bad tensioner or a bad drivebelt could have an effect on the operation of the water pump.
• check the pressure cap on the coolant reservoir tank for good pressure, when you remove the cap you should hear a hissing sound this means you have good pressure in your cooling system, check for corrosion or build up on the cap, clean the cap if nessary, also check the coolant in the reservoir tank it should be somewhat transparent and clean, if not you might need to have the cooling system flushed.
• check the large upper and lower radiator hose's for cracks, swelling, and proper flow. Good luck.

Pull back the carpet in the passenger cabin and feel down under th epadding on the floor, if its moist of wet ou probably need a heater core or have a heter core leak, the part is about $120 for a AC Delco but the job itself is a real ******. Are you using lots of coolant and its just evaporating (or you cant seem to figure out where it is? Then the most likely answer is your heater core) When you do check the passenger floor area make sue you check well as the coolant/water pools and drains, you'll either feel it moist and smell it the minute you put it to your nose or if you taste it from your finger tips i will be really sweet (spit it out dont swallow the stuff) then its most likely your heater core, if you live in a climate where you dont need heat - like me in FL you can try bypassin the Heater Core but thats a temp fix, if that stops your problems HOOORAY you know what your facing, but as mentioned above there can be 10 reasons or more. Best of luck

You could possibly check your fans to ensure they are running. ensure the water pump is not leaking. make sure there is enough coolant in the system. the expansion tank should have some in it. but also make sure there is some in the radiator.