Skoda Fabia VRS - High Pressure in the Cooling System

[antarcticfox]

My VRS is loosing coolant through the Blue coolant filler cap (pressure release valve). I've replaced the cap but it still hisses after a hard drive. I've had the system pressure tested and a new water pump fitted. It appears to be linked to rev's. The harder I drive the sooner the low water warning light comes on the dash. When the engine cools down, the water level occassionally returns to just below full e.g. no low coolant warning light! Where has this coolant gone and returned from!?!?

Typically I'd suspect the Head Gasket, but in reality the coolant system is clean, e.g. no choccy milk shake in the header tank. The oil is clean so not leaking t=in that direction. So it looks like it is being pressurised by something?? But what? Is the cooling system linked to the pressure/induction side of the Turbo??

[bertelli_1]

I'd suspect the head gasket, try running the engine with a coolant pressure tester fitted. You probably have combustion gases leaking into the coolant system. Some garages will have a bit of kit for checking that (a colour changing liquid).

[davepoth]

I'd say HG too, the oil and water don't necessarily have to mix.

[exitwound]

Had this happen to my Corvette.

It was just the fan not coming on when it should and letting the motor run very hot to the extent that it was boiling out of the expansion tank and losing water that way. Replaced it with a new fan motor and a separate control module to let it come on earlier.

Check the fan is coming on when it should, and is running at the correct speed before you pull the head etc..