Right this is a bit confusing and i'm slightly lost on what to do now!

It's been a problem for a while, but it has started to get worse.

Sometimes ill fill the expansion tank and it will use it all in 70 miles, then sometimes ill re fill and it will be good for 200 miles and then ocasionaly it needs topping up after 35miles!

Its getting rather annoying, the engine is getting hot, no sign of any contaminents in the oil, no loss in power or economy etc.....

O yes, and sometimes the light will come on to say its empty at cold, ill open the cap, massive hiss and it all comes flooding back in!

Any help much appreciated as i dont want to be paying a garage lots of my student money!

Cheers.

Could be a slightly blown Head Gasket allowing coolant into a cylinder bore. Worth getting a block test done to see if there are gases in the coolant.

If you have done any servicing to the coolant system recently you could have an air lock. Check to see if both top & bottom rad hoses are getting hot. If the bottom hose stays cold after the engine has reached normal operating temp you have an air lock. If the heater doesn't blow hot air out, that's also a sign of an air lock.

Edited 9 November, 201015 yr by pauldazzle

yup sounds like airlock and possible weeping head gasket,

its not a good idea driving your car like this as you risk serious damage if you run out of coolin/fluid

I'd think airlock, and most garages can do the coolant analysis for you for about £10.