What are the chances my XC60 D5 has headgasket issue?

[Bagheera]

Hello folks,

Bought a 2014 XC60 D5 just recently (documented in another thread).

Other than a few minor niggles, door lock, A/C not working, absolutely love the car.

It's gone to my trusted independent for a cambelt + water pump last week.

Drove fine for the first 30 minutes until i started working the engine hard. Got low coolant warning so stopped within a minute or two. Coolant reservoir is below the minimum and some white steam is coming from the rear left hand side. Top up on the spot and car drives the 30 minutes home just fine.

Out again over the weekend and car drives fine for 35 minutes until we start pulling up a steep and longish hill. Engine temp warning comes on, again some steam but it doesn't feel excessively hot when stop to check. Engine coolant has dropped but not below minimum. Leave it cool for 15 minutes then continue the 5 minute journey to destination. By this point low coolant is on and it's dropped to below minimum. Top up and return the 40 minutes home normally about an hour later.

Gone back to independent today and they've said they'll look over and check the work first. They hint it could be Head gasket because of the coolant loss only at higher rpm and smoke at rear left hand side. There's no other sign of head gasket symptoms though, such as tail pipe smoke, bubbling, milky reservoir etc.

Any thoughts? From what I've read, D5 Head gasket failure is rare.

I'm wondering if maybe a hose hasn't gone back on right or the water pump gasket hasn't seated quite right, but would that account for the loss only at higher rpm? No visible signs of leaks that I can see either.