Is this normal

[maddog334]

Hi All
Can anyone tell me if this normal
When I rev the engine with the blue darlek cap removed the water level in the expansion tank (pressure tank) drops slightly then when I let the revs drop the level comes back up and some times overflows slightly.
I was hoping someone could tell me ,as I know i have a possible head gasket problem at high loads , and am looking for a second hand engine and wondered if this was normal or just a sign that mine has died.

Many Thanks
Martin
1984 1.9 DG

[ambivert]

I think this is normal - perhaps others more knowledgable can confirm it - I have recently used this phenomenon to test that my water pump is working...

[Aidan]

tis normal

[maddog334]

thank you both I thought it was, but wanted to be 100%.
Martin

[vwjon]

ok technical explination.......... when you rev the motor the pump forces the water round the system 'cos the pipes are rubber they expand bigger pipes need more water hey the level in your tank drops!
when you let go of the gas the level returns to normal, the "extra" heat generated by reving the motor expands the water around the engine (very slightly) alot of water expanding slightly will then be passed onto any avaliable space-that would be the expansion tank, oh the lids off so it will flow onto the floor!
when the caps on, this process still happens. feel your pipes when the engine is hot, you'll find them "hard" when the pipes are cold they should be "squeezable".

hope that covers everything for you.