Headgasket failure

[Rik]

So the last few years we've had a multitude of coolant leaks: Waterpump, multiple hoses, cracked header tank etc. Also had to top up the level in the header tank many times, while the overflow tank stays at a steady level.

The new header tank we put in is now completely spherical after the system has been overpressurised. We also see bubbling in the header tank when the cap is removed. Conclusion: blown headgasket.

This overpressurisation is likely the cause of all our earlier failures too. My first question: Is there any other possible cause, besides the headgasket?

Second question: how can overpressurisation happen? Isn't the dalek cap supposed to keep the system at about 1 bar?

Thanks!

[mioba]

If its a JX. The heads cracks between the valves leading to what you describe. Gets worse when hot as the heat expands the cracks.

How old is the head.

Either way you need to remove the head to determine. JX heads can(not) be skimmed. Tolerances are so low if too much metal (over 80 thou) is taken off the valves will kiss the pistons.

[mioba]

As a side. Your blue cap sounds like it failed if a JX. It vents to the tank behind the licence plate and sucks back in.

The main tank should not pressurise to the extend to describe.

Again assuming a JX

[Rik]

Thanks. It's a CS, i figure the same applies then.

It was a new cap, but i've heard before they're often a bit "pooh" quality

[mioba]

Same applied with a CS.

Are you handy to DIY and have Bently.
These engines are damn eaay to work on if you can the above.

[Rik]

Relatively handy but no experience with the insides of engines.

I do have the Bentley as PDF somewhere, I'll check tomorrow. I feel I can probably do most of the stuff but I am a bit scared of everything to do with the injection pump.