QuestionJosh, I opened the air system as I replaced the fan clutch, the timing belt, water pump, thermostat and changed the transmission fluid and filter. I tried to bleed the cooling system by pouring in antifreeze until it came out of the bleed screw (screw all the way off ). I had to rock the car back and forth, let the car run and shut it off and reapply antifreeze until the it came out of the screw. I then tightned the screw and followed the directions of letting the thermostat open and bleed the air out,,,steam blew out of the bleed hole, no bubbly water,,,yet the car still overheated really, really quick- in the red!! Did I bleed the air out the right way? Is there some other cause for the overheating? Thanks much. Chris 1988 BMW 325i convertible.
AnswerChris,
Make sure you have the heat on, as bubbles will get trapped in the heater core.
Have someone watch the heat hand while you do this, do not let the engine run hot, it will warp the head and then you will have much more problems than trapped air.
I would take the thermostat out (below the bleed screw) and boil it to make sure it works. I know some people drill a pin hold in the thermostat to allow some of the air to escape.
Chances are that you got a large air pocket in the block that is hard to dislodge. And since there is air in the engine, it's allowing steam to build, and over heat.
I have always had luck by filling the coolant tank, and then squeezing the coolant hoses quickly to "slosh" the air out. I would do this first without having the engine running. You should see quite a few bubbles come out of the coolant tank. Then I would open the bleed screw and let any air out that was under pressure. Now turn the heat on inside the car, and start the engine. Have someone sit inside and watch the heat hand, if it goes above 3/4, stop the engine. While the engine is running, keep sloshing the hoses so it will dislodge any air pockets and keep refilling the coolant as it goes down.
Hope this helps,
Josh
