High pressure in water coolant

[08Kev]

Hope someone out there can help me.

The engine is a 1.9 turbo diesel, When the engine is running at normal temperature, air pressure is being pumped out of the expansion tank and into the water resevoir, am I right in thinking that this shouldn't happen?, the cap is working as it should, the engine starts and runs ok, no smoke, the water in the resevoir is cold, no water in the oil, or visa versa.

Any comments or suggestions are greatly appreciated.

[Red Westie]

The expansion cap is set to around 2bar and under normal circumstances the system wouldn't reach this pressure. System pressure is generally a good thing as coolant under pressure boils at a higher temperature so can retain more heat without boiling.
However, excess pressure/bubbles in the coolant can be an indication of head gasket failure.
You could try a coolant pressure tester but I would be tempted to change the main pressure cap first to be sure it isn't opening too soon.
Martin

[08Kev]

Thanks for your advice Martin, the cap and expansion tank is new and pretty sure it's working as it should, I have recently had a new head gasket fitted, van runs OK and doesn't seem to overheat, could it be something to do with the bleeding of the radiator which I have read about on this site.

[t25darren]

Hi There
Sounds like a head gasket to me--1.6 D? common problem, What gasaket was fitted and was the head checked for cracking?

Darren

[jimbovw68]

Hi
I had same problem high pressure in water system 1.9 petrol
I made a Head Gasket tester from a old blue delek expansion tank cap,some hose and a shot glass full of Tester Fluid
Tester Fluid £10 from Partco
Bubble the gasses through the fluid if it turns orange/yellow it indicates carbon dioxide gas in coolant

Please do not try this if engine is at pressure or hot,you will or may get burnt

[08Kev]

Thanks for all your replies, I'll try the tester fluid thing, at least it will narrow it down.

Cheers.