Has my head gasket gone (90 N/A 2.5D)

I'd be grateful if someone could confirm this for me before I start stripping the head down!

-Temperature gauge is almost into the red after 5-6 miles of driving
-Found the coolant reservoir to be empty
-Foamy white residue on the dipstick, but oddly not on the filler cap (which I expected)

Are there any other checks I can do to confirm the dreaded head gasket has gone?

Cheers guys

fill it up run it and look for visible leaks, if you have unusual white smoke or excessive condensation / steam as well

Thanks for that.

Always had white smoke on start up, but thought that normal for a diesel 90!

White smoke on start is unburnt fuel, your looking for white smoke running and antifreeze smell in exhaust.
Fill it with water and look for external leaks, you can replace coolant when you find leak or you will need to drain coolant to replace head gasket.

But for diagnosis there is no point putting coolant in to top up-you should not run engine on straight water other than diagnosis as it corrodes and scales internals over time

Sorted! Bizarrely!! Topped up the reservoir and ran the engine for 30 mins. Clean as a whistle - not a puff of smoke.

Temp back to normal, no leaks, and I re-checked the dipstick - no white muck on it

Thanks for the tips. All back to normal and delighted not to have to be doing a head gasket job

Lucky, hopefully you didn't overheat it whilst it had no coolant in it. Thankfully the N/A is a pretty tough engine, should be alright.