Pressure again
 

Greyscale hasn't moved or been started for two days, as I am away tomorrow in her for 5 days I did a pre-trip check, and on releasing the coolant cap heard a slight, but noticeable hiss of pressure.

On inspection the coolant level was up just below the filler neck, well above the "Fins" where I know she was filled too. No coolant has been added since she was serviced and the coolant changed.

Any ideas?

The coolant was over-filled, so should be adjusted to the correct MAX mark. This is at the base of the fins. There should be no residual pressure in the cold system, but do the test again with the correct inventory.

After a drive, allow it all to cool down at least six hours and preferably overnight. Check for residual pressure.

TC

Its level was below the fins last check- and none has been added? that's whats confusing me

There will always be some variation due to changes in temperature and even atmospheric pressure.

You mean it was at the bottom of the fins one day and after driving and standing, it was at the top? If so, I'd say that's a worrying sign.

TC

yup that's what I am saying ! :(

What was the ambient temperature when you previously checked it compared to today? You might be surprised how much water expands with even a little extra heat introduced and its certainly been considerably warmer here for the last couple of days.
Try checking it later this evening when the temperatures drop a little before you start worrying too much.

Its not that hot here today , although quite a bit warmer than when I last checked it, took it out for a spin and the temperature stayed within her normal parameters- 95-98 - will see what its like tomorrow morning once she has cooled down again.

You might find you get a little hiss of air inwards when you check it so don't naturally assume its pressure rather than vacuum :)

Am no expert - and i am sure T-Cut will advise but you seem to be running hot - my Turbo 1.8 runs around 90 - also cannot imagine the ambient temp to cause an expansion in water volume from the bottom to the top of the fins - i would think air or exhaust gas - is your coolant nice and clear and does the expansion tank smell of fuel/exhaust?