Got it sorted for a short while, it’s not the head gasket as the car has covered over 5000 miles in the time the issue has been present and has not gotten any worse. If it was HGF it would have gone completely by now I’m sure.
Narrowed it down to a partially blocked heater matrix, due to the...
The car usually takes a while to warm up this hasn’t really changed since the problem started. The 2.0tdi engines are really thermally efficient.
I have thought about the thermostat however I would expect to have overheating issues if that was at fault.
Yeah I believe the coolant must be boiling in the system somewhere. When I opened the cap the other day when I noticed the level low. (Not noticed this before it’s usually fine or gone) it bubbled and level then had a rise of about 5mm saying there is air in the system. But not sure where it is...
The level will stay fine for maybe a week at a time (the car does quite a lot of miles a week) then seems to dump the header tank out when engine is off.
Had a compression test done on the cooling system and it stayed solid. Also replaced the cap just in case the relief had started to fail...
Check brake fluid level if it's low then the fluid could be dipping below the sensor level when accelerating hard or turning. The brake warning light will only flash for a fraction of a second and is easily missed
Sounds like the warning buzzer when the handbrake is left on, do you know if the brake warning light flashes on too or not?
If it isn't the handbrake left on, check the brake fluid level as it will beep when it's low when going around corners breaking or accelerating.