Coolant loss

[Haydn1]

Xc60 2010 D3. Coolant level warning light regularly comes on. Coolant level is below minimum. But when engine has been allowed to cool and the pressure cap is released the level returns to just above minimum. Has happened repeatedly, I have a top up bottle of coolant but have only used 0.5litre in 2000 miles. Had a pressure test, all ok. Had a dye test, shows hydrocarbons in coolant but I’m aware that this isn’t conclusive. My suspicions are either air lock in cooling system or head gasket fault. One is minor and presumably cheap to fix ( not sure how) the other is big cost and once started down that road I am committed. How do I differentiate? Or could I be wrong and it’s something else?

[Listerit]

If you had a leak test done and there is exhaust gases in it. Then the head gasket is gone .

As the top up is minimal you most likely will not require a skim on the head. It's just gasket change . I had the exact same on my D2. See thread on main page.

Repaired last week. Not a drop lost since and car is running great.

[Austin160]

Simple things first:- worth renewing the reservoir cap with a new Volvo one. Might not be a fix, but worth the expense.
Head gasket issues? Personally, I would certainly not jump to that conclusion as the most likely issue.

[Haydn1]

Thanks for the feedback. Replacing the cap; yes I’ve already tried that. Seems to me that there must be air or gases involved somewhere to cause the big variation in header tank levels because coolant liquid is relatively incompressible. Can’t see a way to bleed out any airlock though. Tried running the engine with the cap off for a while but that didn’t work.

[Listerit]

Originally Posted by Austin160

Simple things first:- worth renewing the reservoir cap with a new Volvo one. Might not be a fix, but worth the expense.
Head gasket issues? Personally, I would certainly not jump to that conclusion as the most likely issue.

....

Reservoir cap ??

If he has detected exhaust gases in the coolant then yes he is has gases getting into the coolant system.

Most likely head gasket or water pump.

It's not really rocket science. Replacing caps won't make a jot of a difference. In fact it was a waste of money.

[Listerit]

Originally Posted by Haydn1

Thanks for the feedback. Replacing the cap; yes I’ve already tried that. Seems to me that there must be air or gases involved somewhere to cause the big variation in header tank levels because coolant liquid is relatively incompressible. Can’t see a way to bleed out any airlock though. Tried running the engine with the cap off for a while but that didn’t work.

Simple. Flush the collant. Fill it up again with new.

Then do the gas test again. Per instructions on the tester kit..it takes a few minutes.

If you have colour change then it's the head gasket.