Boiling over...

[Benrevs]

Before anyone says "search" I have tried everything I know of.  I know its a vr but the principles are the same?  My header tank keeps boiling over way before the fan would usually kick in( just below half), also the level drops with a bit of revvage. I have changed the stat and the fan switch but hasnt made a wank of difference. I have flushed the block and the rad and all flows fine as does the heater matrix.  The rad also warms up where it should do, have a sniffer on the header but came up negative for headgasket.  Could a sketchy water pump cause this? Car runs fine also and no sign of head crackage etc..  Something I am over looking here??  I have the rad fans on a manual switch in the car for the moment. Ben

[Dan34]

im no expert lol but could it be a dodgy cap on the expansion tank?

Dan

[Mr Blue]

I used to get this with cheap coolant from halfords. The concentrated blue stuff.

Try the pink G12+ coolant from vw. Its cured this problem on mine. wierd

[Conker]

Just a few ideas...     PS Saw you parked up on the layby just past J17 a couple of weekends ago.

> Did you upgrade the rad and fan when you fitted the VR?
> Can you see a strong squirt of coolant into the expansion tank when you rev the engine i.e. the water pump is working. I presume this is possible on a VR??
> Whats the heater like? Does it get hot?
> Any leaks?  (Prevents pressurisation)
> Does having the fan on manual prevent boiling?
> What are the temps like when it bolis over? If they are okay, its probably just a new cap/tank thats needed.

[monzablue16v]

Expansion tank cap.