Coolant Expansion

[jphaigh]

hello,
got a 1990 300E 2.6 with a little coolant prob.

when i fill the coolant to the 'Full' mark and the engine gets hot the coolant expands and flows out the overflow outlet. then when the engine returns to a lower temp the coolant level is about a full inch lower than 'Full" mark (or what ever level it was beforehand.

any explanations you could provide would be great

thanks,
David

PS. i must say, this a great site! glad i found it.

 

[Ian B Walker]

You most probably have a small air lock in the system.

 

[television]

A easy way to get any air out is to remove the filler cap and squeeze the bottom hose pipe, keep doing this and any air bubbles will come out.

Dont worry if it stays a touch under the level, if it keeps blowing water out then there could be a head gaskit problem where the water is being blown up.

Malcolm

 

[Ultymate]

If it's not an airlock as mentioned by the guys above you could have a faulty pressure cap on your expansion tank you can get them tested if you know someone with access to a cooling system pressure tester, that said they're cheap enough to buy so rather than pay someone to test it get a replacement and fit it, does'nt have to be dealer, Halfords or accessory shops sell them. They come in two different lengths and several pressure settings make sure you get the right one for your vehicle. If that does'nt cure it you maybe have the start of a head gasket issue.

P.S. Don't overfill your expansion tank without the correct airspace in the tank the system cannot build up the required pressure for correct cooling