how do i bleed the cooling system up?

Post Sun Jun 25, 2006 10:32 pm

i drained the coolant on my '85 320i and refilled it with the correct mix of antifreeze and water but i now have the coolant light on and it idles high (1600rpm! i assume it's got an air lock somewhere).
do i just open the screw on the bottom of the rad and keep topping up the header tank until all the air is out?
any help is greatly apprieciated as i'm rather new to this bmw lark

Post Sun Jun 25, 2006 10:48 pm

park facing up a hill if poss
or raise the front slightly

then open the screw on top of the thermostat housing

set the heater to full power
and refill the water

when no more bubbles are coming from the bleed screw tighten it up
and run the car keeping an eye on the temp gauge and also make sure the heater blows hot air

check water levels again
and temp gauge is no further than half way

all is done

Daz

Post Mon Jun 26, 2006 1:16 pm

dazleeds wrote:park facing up a hill if poss
or raise the front slightly

then open the screw on top of the thermostat housing

set the heater to full power
and refill the water

when no more bubbles are coming from the bleed screw tighten it up
and run the car keeping an eye on the temp gauge and also make sure the heater blows hot air

check water levels again
and temp gauge is no further than half way

all is done

Daz

Right.. I can't even get any bubbles to come out of the bleed screw!!

AND my temp guage only gets to the first line before 1/2 way! WTF??

Post Mon Jun 26, 2006 1:24 pm

I think the bleed screw is by the thermostate on an m20? Its not at the bottom of the rad thats for sure!

I find it easiest to make sure the header tank is as full as possible at all times.

make sure your V belt is tight enough and the pump is in good condition.

Did you clean the system out and make sure there were no blockages?

Post Mon Jun 26, 2006 3:17 pm

whats the best way to clean the system?

Post Mon Jun 26, 2006 9:09 pm

Don't think either of your problems are actually to do with the coolant change, or that there are any problems with the cooling system at all. Just a result of disturbing things in the engine bay.
Low coolant light is probably a dead sensor, which was nearly dead before, and the high idle could be a number of things - even something as daft as you've moved the throttle cable and left it tight so that the throttle doesn't close properly.
Temp gauge on the first line on the gauge is fine.