More overheating problems (I searched!)

[Nygdup]

The saga continues with my overheating problems. I replaced the thermostat and fan clutch last week when I first overheated. My car continued to overheat and at first I thought that I'd blown a head gasket. However, I've run the car several times since then and have yet to see any oil in the coolant or coolant in the oil, nor am I getting steam out the exhaust.

Sitting in my garage the other night I noticed that the car actually cooled down if I was giving the car gas while in neutral rather than letting it idle. I've tried bleeding the system two or three times, no change. Thoughts?

[jlevie]

What you describe could be from a thermostat that isn't fully opening, air in the cooling system, a bad fan clutch, or partial failure of the water pump impeller. I realize that you've just replaced the fan clutch and thermostat, but even new parts can be defective. The clutch is easy enough to test by seeing if it engages when the radiator is hot. You'd have to pull the thermostat to test it. And of course you can't inspect the pump impeller with it in the engine.

Do you still get air out of the system when you attempt a bleed? Having air being released over successive bleeds could indicate a small head gasket leak.

[Nygdup]

I've done the fan clutch / rolled newspaper test. Fan clutch is good. Last time I bled the system I didn't seem to have any water in the system. I wonder if I'm bleeding the system wrong.

I open the bleed screw, fill resevoir, tighten screw, run the car. Repeat until coolant comes out of bleed screw and resevoir is full. Last time I ran the car overflow came out of the puke tube immediately.

[jlevie]

Try the procedure below. If successive bleeds using that procedure yield air the possibility of a head gasket leak increases.

1) Using ramps or a jack get the front of the car 1' or more higher than
the rear. That will make the radiator and bleed screw the highest point
on the engine and facilitate removal of air.

2) With the bleed screw open, add coolant until no more air comes out of
the bleed.

3) Leave the filler cap off, or at least loose, and set the heat for max
temp and fan speed. Leaving the cap loose will prevent air that's still
in the system from causing a "coolant fountain" once the engine heats
up. Start the engine and allow it to warm up to operating temp. As it
warms up occasionally crack the bleed screw to release any air and top
up the coolant as necessary.

4) Once the engine is at temp bring it up to 2000-2500 for a few seconds
several times. Then crack the bleed until no more air is released. At
this point the heater should be throwing lots of hot air, which
indicates that the heater core is filled with coolant. You may have to
repeat this a few times to get all the air out.

5) Drive the car a bit, allow it to cool back down, and recheck the
bleed for air. Over the next few days you may get very small amounts (a
few bubbles) of air out of the bleed screw.