Coolant loss mystery

Been losing coolant when the engine is warm. Can see no leaks, oil is fine.

My thermostat is wrong due to conversion which i need to sort but could this be the cause? Coolant feels cool in header tank and rad is warm. Levels change when hose squeezed. No airlock in rad either.

Strange thing is same symptoms in my transit connect only more dramatic loss of fluid level.

Erm help

Cheers

Nobody?

Cant think of anything other than what I suggested mate unless because its the wrong temp sender and not fully tight coolant is leaking past there when hot and running but evaporating so fast you cant tell when stopped as it leaves no puddle ?

Hmm possible. New sender when i get home. Tried several now.

May be water pump seal only leaking when hot and revving ! Is there a dirty line from the tell tell hole below the pump!! Seals failing bearings usually follow!
Other things to check are behind cylinder head near bulkhead feel there for leaks ! Replace expansion tank cap !! May be letting go too early!! If all things look ok then you need to get the system pressure tested !! Five minute job at most garages ! Should show up any leaks etc !!! Hate to say it but it could be failing head gasket too !!! Let's hope it's a simple fix!! Good luck.

Hmm. Will sort thermostat and change cap as it is an ancient header tank and using the td header I had originally. No signs of water pump failure. Could be the pressure from the tdi is more than that of the old td so more pressure to that cap.