Not sure, it has had a recon turbo though

Turbo isn't water cooled mate.

Have heard of the EGR causing similar effects due to being cracked, however:

- isn't water cooled on this

- have tried with an EGR delete and no change.

The fact the header tank bubbles the fluid in bottle suggests HG to me, or head or whatever. :)

Possibly, or maybe there's a leak somewhere in the system so it's not pressurising properly. My old Saab used to do it, though it was slight - probably 500ml of water every month or two. Eventually the pipe with a pin hole in it properly let go and after replacing it everything was fine.

Was the coolant fully flushed and changed after the HG and head were done?

Dunno man!

Pressurised it to 1.5 bar when warm earlier, in 20 mins it lost 0.3 bar.

Hmm! Haha

Tried some k seal ting earlier! Seems a little better - but still fucked.

Stopped for a mid drive looksies and the header tank above the coolant level just looked like frough, you don't get a nice steady stream through the top return hose, kinda looks aerated.

Also; just seemed to me a minute ago the header tank fluid was like warm and coolant pipes etc hot.

Still thinking Waterpump tbh!

UPDATE: (if anyone's still paying attention?)

Flushed the whole system today.

Changed thermostat - when doing so I could feel the Waterpump impellor and it's all intact and fine.

It never goes above 90 degrees, fan works; heater hot.

Waterpump & stat ok.

Will still pressurise (pipes hard) and air leakage from pressure relief on header tank.

When you've been giving it some, higher rpms/more boost it will overflow coolant out.

Going to try a new header tank for the sake of them being cheap.

It must be cylinder leakage surely?! But NO other symptoms.

Starts fine.

Coolant clean.

No misfires or bad running.

No steam at all from exhaust.

It developed this fault, and does the same with another head and obviously HG was done at the same time.

Cracked block?