car overheating

[kmac2304]

i have an 03 pontiac grand prix gt with 3.8,replaced water pump and thermostat car still overheating! Both cooling fans work fine,was told that their may be air in cooling system. Is this an accurate diagnosis?How do i bleed air out of cooling system?

[GTP Dad]

Air in the system will cause it to continue to overheat. Find the top radiator hose where it attaches to the block. There should be a screw in the top. Usually an allen type plug to be exact. Start the car and run the engine while the plug is loose until you see coolant come out. Make sure you have the reservoir full and the level should drop as the air bleeds out of the system. This usually works best with the engine pointed up hill and the heater on full. Once you see coolant coming out where the plug is close it and repeat as necessary. You may need to do this several times to get all the air out.

These systems can be a real pain to bleed but with a little patience you should be able to get the air out.

[CrazyHorst]

My info on the heater core is that it "heats" all the time...just a matter of whether the air flow doors are open or not.

In other words, there is air control but not an actuated flow control for the water side. There is a special geometry rubber washer inside one of the fittings which acts as a flow control (really a flow-limiter) for higher RPM operation so any core sand entrained in the water jacket flow stream does not wear out the heater core prematurely.

However the idea of getting the nose of the engine up is good. When I bleed, I did it several times (like 4 separate times on successive days). Just take a bundle of paper towels and crack the bleeder...the towels will get soaked and hot but eventually you'll get all the air out.