1.8cl expansion tank boiling over but not overheating help.

[ruffryder]

Ok the water tank keeps boiling over but car doesn't overheat. I've change the thermostat an it hasent solved it, I bypassed the matrix still same prob, the bottom hose on rad to thermo never gets very warm can any one help don't know what's wrong with it now would it be the rad

[thai-wronghorse]

Sounds like you might have an airlock somewhere.

[Bellend]

If the gauge is reaching the correct temps, the header tank cap seal could be broken.

This could also be why it's not getting warm as it isn't pressurising properly.

[ruffryder]

Yeh the fan kicks in aswell water comes out of a heather hole bit on side of tank or should that not be a hole lol. The heaters only come out cold but temp gauge goes about half way there's no bleed valve on any hoses

[Screech16v]

Does sound like a dodgy cap,get a new blue one to start with,if your old cap isnt sealing then the system will not pressurize allowing the water to boil ,fill it back up leave cap off and run it up,massage the pipes sqeezing the air out ,top up as needed then put the cap back on,see how it goes 

[ruffryder]

Ok cheers tried that with blowers on but still did it i hsve a spare header tank ill try