I am not familiar with the anatomy of this engine but unless there is another way by which the coolant can escape and be contaminated apart from via a failed CHG, the answer to the question is, yes.

I took it out for a 15min run around the block and white smoke was pouring out the back, checked the coolant and it had gone below the Min mark after I'd filled it to just under the max also it had turned a brownish colour.

Strange thing s the coolant has also returned to the same level after leaving it to cool.

Engine bay was very hot too around the turbo area.

I had it idling and it doesn't smoke which is odd and coolant seems OK.

Any ideas??

My best guess for your puzzling coolant level recovery is that a gas/air pocket is displaced/lost from the running engine, which, together with some coolant loss, lowers the coolant level.

Later on, combustion gases get into the cooling system and displace some coolant into the reservoir, raising its level again. This would imply head gasket breach or crack CH/block.

Not very convincing, but the best I can do offhand.

Thanks, appreciate the comment.

Ive drained the coolant today as it was awful, brown and smelly shall we say!

Shame really as the rest of the car is in good order but never mind.

I suppose an alternative explanation for the puzzling coolant level recovery MIGHT be that oil is replacing lost coolant. This would imply you were loosing oil from the engine.

Do you have a definite indication of oil in the coolant?

Rust in the coolant is quite common on old engines and wouldn't have much diagnostic significance or threaten immediate engine death.

Oil in the coolant is significant diagnostically, but, while it will reduce cooling efficiency, it doesnt itself threaten immediate engine death.

Coolant in the oil is similarly significant diagnostically, and, since it will reduce lubrication efficiency, could itself threaten immediate engine death.

If your oil and coolant are mixing via an oil cooler that would probably be easier to fix than a head gasket, but unless I'm missing something its hard to see how this would put much coolant into the combustion chambers, which your white exhaust smoke seems to imply.

There would be some getting in past the rings, but I'd doubt it would be enough to match your reported symptoms, though I could be wrong.

Edited by edlithgow on 20/06/2022 at 23:35