well i could hear hissing coming out of this when it was cooling down. how would it cause the header tank to fill then drain (apologies, this is my first dealings with coolant systems!)Shaun said:It could just be a weak rad cap so try that first but if theres oil deposits in there then theres a chance of it being the head gasket
there`s a small amount of "smeggy" crap around the sides of the header tank where the coolant level has been up before. i`ll try the flush and sealant thing as i ain`t loosing water and there`s no sign of water in my oil either.PobodY said:It's one of two things:
Something is boiling somewhere (which might explain why you can 'burp' the system.
There's exhaust gas getting into the coolant. - If it's looking particularly rusty there's the chance that the jacket has corroded and there's a pin-hole leak for the exhaust to get through.
You could try a coolant flush just so see if there's a blockage somewhere... and whack a bit of sealant in the mix to block any small holes when you top it up again. Or just grind some black pepper into the radiator cap - it's an incredibly effective ghetto fix.
After a while the springs tend to go weak and as the water heats up it expands creating pressure as the spring is weak this will allow the water to fill the headtank whilst hot and will drain back into the system as it cools because the water shrinks as it cools creating a vacum and drawing the water back into the rad.On the other side,if the head gasket has gone from cylinder to water jacket the compression and combustion process over pressurise the water system creating the same symptoms.olliecast said:well i could hear hissing coming out of this when it was cooling down. how would it cause the header tank to fill then drain (apologies, this is my first dealings with coolant systems!)
Oh yeah - good point, I'd forgotten about that. My brother-in-law is a plant mechanic, that's how I knew that it was exhaust getting into my coolant!markweatherill said:If your friendly local garage has one of those exhaust gas 'sniffers' that look like a turkey baster, it's a quick and easy test for exhaust gas in the coolant.