just bought a 99 eldorado 122k miles last month and upon buying it i was told that they had to replace the waterpump b/c the car had over heated on them. but the car appeared to be fine now. but it never runs with a temp where the gauge is rite in the middle it is always a little bit off to the rite towards hot but not that much. but when i was sitting in a parkin lot the other day after running the car for a good while it overheated to 3/4 then cooled itself back down. and now it does this ocassionaly when i let the car idle a while after i run it hard or after all day driving. when it is at 3/4 the way over heated and i push the gas to bring the idle up and instantly back off it seems to start cooling down prety rapidly. i also had the car pressure tested it came back good. also dont no if this is related when the ac is on the drivers side dont blow nearly as cold as the pass side infact it is still quite warm.
any help would be appriteated thanks in advance joe

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It does not seem as though your engine is overheating. An overheating engine would be kicking up a fuss and spewing steam out the radiator. Northstar engines run a bit hotter than what you might be used to. The cooling fans kick on at 225 degrees so up to that is considered normal in a Cadillac Northstar. By accelerating the motor the water pumpcirculates coolant through the block and rad so it is normal to see the temperature come down when doing that.

 

Your AC problem is likely the blend door motor not operating properly.