C20let boiling over

[BENDOGGER]

Right guys I have a c20let in my nova taxed it at the weekend went out in it and when I stop the engine after a drive it boils over and out of the header tank.

When I'm driving it the temp gauge looks ok fans come in ok and heaters seem to be working. What could cause it to boil over when I stop?


Airlock or could it be worse?

[Edd]

cap on header tank ok ? seal in good condition ?

[BENDOGGER]

That I dunno but still surely it shouldn't get that hot should it? The tank itself looks like its expanded out if you get what I mean

[mowgli]

the system is meant to be pressurised. a fully working rad cap can run some serious pressure before leaking, so either its failing, or its got a cooling problem & is overheating when stationary.

[MK999]

Could be a sign of low flow through the system, fine at RPM with the water pump going well, but slow down to idle and the coolant sits against the hot cylinders and boils up.

Stat, rad and pump are the ones to check in this case, try the header cap first, it's cheapest.

[BENDOGGER]

Right il try a new cap at weekend where's best place to get one

[MK999]

I'd hazard a guess than Vauxhall only change their header tank caps every 15 years or so, so try a dealer, it might surprise you. Even then only because coolant pressures have been going up on modern cars.

I very nearly unscrewed one on a Volvo courtesy car to check it had pressure after it spat out some water from the air con (this was alien to me, normally when cars drop water it's bad) then I saw the 25 (!) PSI warning on it and thought fook that lol

[mowgli]

mk... most post 2000 cars spit water out of the aircon...

[MK999]

Funny coincidence, I ignore most cars built past 2000 that don't come with an MSA/FIA book :d