Coolant problems

[g0cew]

The Coolant System is getting pressurised . Level drops after running engine and rises when cold and reservoir cap released.

3 possibilities.

Reservoir Cap faulty. Should keep System pressure at a set level when engine running. When cold pressure would drop and air let back in through pressure cap.

System being pressurised due to an exhaust gas leak also loss of coolant as it is sucked into engine. Cylinder head gasket.

EGR cooler leaking.
https://vwcaliforniaclub.com/threads/loss-of-coolant-egr-valve.22844/

I got a stone thru the grill punctured radiator since that I've fitted mesh to stop it just a thought

 

[Christine Kirk]

What happens if you undo the cap on the expansion vessel?

The coolant level stays in the same place! I watched the technician test the cap so it appears to be okay; the cap comes off without any problems and as the engine was stone cold there was no pressure behind it!