Overheating

[Big Eb]

Hello again,been a while, the wife's car.
Doris 2.0 hdi yr 2000.xantia.
Was overheating,replaced thermostat and still seem to be overheating. Car hasn't been run for nearly 2 Weeks thought I'd have a look today and after opening expansion tank water everywhere as was still under pressure, enough to spurt out the water at quite a force not just a little fizzle. Any body any ideas why.
All help greatly received.
Cheers Eb

[RichardW]

Sounds like the head gasket has gone.... Unusual on a 2.0 HDi, but not unheard of.

[Big Eb]

Hi Richard,if it's gone would you get the usual mayo around the expansion tank cap.
Cheers Eb

[Big Eb]

Also around the oil filler as both are clear of the dreaded mayo

[RichardW]

You only get mayo if you've got a minor leak from the water jacket into the oil ways. By the sound of it you have a major leak from the cylinder into the water jacket. You already failed the first test ( remaining pressure when cold) but you could try running it with the cap off to see if there any bubbles coming into tank, then sticking the cap on and running for a minute to see if it builds pressure without heating up.

Pretty sure it is time to decapitate it however! I fear you may have warped the head with such a big leak though.

[Big Eb]

Did that couple weeks ago after putting new thermostat in,and got hot within 5 mins of purging and temp going in the red