how do I get rid of air locks in the cooling system???

[325i-sport]

I have just installed a replacement engine into my 325 and i need to get the air locks out of the system? what is the best way to fill the car up with water and to bleed the air out, it was pressurizing last nite and temp on the instrument cluster was going over half, i openned the rad cap and it was just spewing over the top.??? any ideas will be welcomed

[Simon]

After filling the coolant system, get the engine up to running temperature, and make sure the heater is set to full red.
Switch off the engine and undo the bleed screw on the thermostat housing and leave any air bubbles escape until it's just coolant escaping. Leave the engine to cool and then top up with water.

[325i-sport]

ok cheers i will give it a shot tonight.

[Toby_Unna]

agree with all simon says. make sure the car is fairly level (i.e. not on a steep driveway!) and take the coolant filler cap off before you undo the bleed screw so the coolant can flow out uninhibited.

I usually undo the bleed screw with the engine running for a few seconds after bleeding normally, just to be sure. air locks are *bad*!

[325i-sport]

after the car reaches norm running temp, wouldnt taking the cap off just realese the pressure and hence no air would come through the bleed screw

[Toby_Unna]

see what you mean, i didn't read simon's post properly!

i don't bother getting the car warm - just fill it cold, with the bleed screw open and the cap off, then when it's full and there's no air bubbles coming out put the cap on and tighten the screw, then start it and rev it a bit to flow the coolant round, then bleed it again with the cap off

[Brianmoooore]

Airlock happens in the top heater hose. If all else fails, with the engine cold, loosen the heater hose clip and pull the hose just short of coming right off, so as to let the air out. Process can be helped by pulling the overflow hose out from the inner wing, removing rad cap, and getting someone to put their hand flat across the filler neck and blow hard into the overflow hose at the same time.

[Dom]

Here's a good one.

I've fitted the big bore throttle body to my iS and removed the heater thing around the tb, capping off the pipes with bolts. Now my heater doesn't blow hot air and the engine site slightly above middle in traffic when it was below before. Air lock? Or do I have to connect the two pipes together?

[kidsinister]

Not 100% sure, but if you're bypassing something and you're left with two pipes I'd say connect them rather than block them off. After all, what's in the pipes needs to go somewhere.

[Dom]

Yeah, will reconnect them anyway and do a quick bleed as a matter of course. Is due it's annual inspection too...

[Geeman]

Dom no!

Connect them back up again! You've got to allow the water to flow round still...

I did the same thing as you with the TB heater plate, but connected the pipes back up, all be it in a much simpler manner to the existing set-up...