Looking for some help please. Recently had a leak in my radiator (MK) that has been fixed.

However now after a short run when I stop (engine still running), the coolent overflows through the header tank. The engine is a 2ltr pinto with a VW header tank. Any help in solving this would be much appreciated. Did not do this prior to the leak being fixed.

Regards,

Arnie.

How did you fix the leak?

Has your head gasket gone? - this could pressurise the coolant and cause it to over flow.

Failing that is your thermostat stuck and causing it to overheat?

Leak was in the top rail on the radiator. Braize had not taken fully and as a result small pin hole which was rebraized.

Do not think head gasket has gone as it seems to run okay with plenty of power. Not sure about the thermostat. Will check this out.

It sounds like you could have an air lock.

second the airlock, its probably in the header of the radiator

is the cap on your header tank black or blue?
when i had my corrado the header tank on that used to overflow it turned out the seal on the cap goes after a while and can cause lack of pressure, you can get an upradted blue cap for them simple although on mine the seal had just got twisted on the cap itself just needed untwisting might be worth checking first

[Edited on 1/6/09 by corrado vr6]

It is a blue top. Will check out the seal. Are all the blue ones the same pressure? If so will try and get a replacement. I assume available at a VW dealers.

If it is air in the radiator top what's the best way to clear it?

Thanks for everyone's help much appreciated.

Regards,

Arnie.

The cause is heat soak causing local boiling once the engine is stopped and the coolant no longer circulating..

A few things you should check

(1) Ignition timing -- check it isn't excessively retarded --- reatarded timing causes excessive heat rejection to the cylinder walls ie waste heat that should get lost in the exhaust gasses gets dumped in the cooling system..
(2) Have you got by-pass hose fitted -- this allows some internal circulation by thermosyphon even when the engine is stopped..
(3) Check you have all the air out of the system.

[Edited on 2/6/09 by britishtrident]

My crossflow did it a few times after filling for the first time - every time it was an air lock.

In my case, I had to drill a tiny air hole in the thermostat body, also squeezed various water hoses as the water was poured in, etc. etc.

Once all the air was out, the water level in the overflow tank went up and down entirely according to plan.

So - another vote for an air-lock somewhere.

[Edited on 2/6/09 by David Jenkins]

Thanks for all the responses. Turned out to be a dislodged and twisted O ring as corrado vr6 suggested. Thanks.

Regards,

Arnie