Coolant overfill...

[jimmy156]

So i had a slight hose malfunction today which explained why the fan belt was squeeking for the first 15 minutes of the journey but also left me by the side of the road waiting for some water and a screwdriver to re-attach said hose.

Anyway... Got home and i have topped up the cold engine with what i thought was the right amount of coolant, put the cap back on and turned the engine on to let it warm up/mix/ensure no further toping up was necessary. When i nipped the cap of the coolant to check the level (the expansion tank is opaque with age) the coolant moved right up to the level of the cap. When i restarted the car it started to bubble out of the open filling hole.

Have i overfilled it, or is this normal? Is there a way to drain some out easily?

Cheers, James

[Eighteeteewhy]

Wait until it has cooled and check again. You may have some air locks in the system.

[skyrover]

A bit of overflow is normal just after filling the bottle/radiator as the engine pressurises the system and pushes any air bubbles out.

You should have an overflow pipe which will prevent the pressure building up and cracking your expansion tank.

[jimmy156]

Thanks guys, i will go back and check shortly

Good to know there should be a pressure release too!

[W41RU5]

Might be worth replacing the cap if the problem persists, my E46 kept frothing coolant and the levels were soaring all over the place so changed the reservoir cap and bled the system and it was fine. Emphasis on correctly bleeding the system or it can cause all kinds of issues.