Have a 54 plate fabia VRS TDI runs fine part from water leak have got water being forced out the expansion tank doesnt overheat heater is good lots of hot air think I may have either an airlock or a blocked rad or a water pump problem have had a head test and that came back fine so its not the head gasket I have got a good stream of water coming from the small top hose on the expansion tank straight from cold it seems that the coolant only leaks when the engine was under load not on tickover a full tank of expansion tank water will last bout 30 miles before the warning light comes on I know basic mechanics but this I'm a little puzzled any help would be good

Edited 1 January, 201214 yr by skodavrs54

Have a 54 plate fabia VRS TDI runs fine part from water leak have got water being forced out the expansion tank doesnt overheat heater is good lots of hot air think I may have either an airlock or a blocked rad or a water pump problem have had a head test and that came back fine so its not the head gasket I have got a good stream of water coming from the small top hose on the expansion tank straight from cold it seems that the coolant only leaks when the engine was under load not on tickover a full tank of expansion tank water will last bout 30 miles before the warning light comes on I know basic mechanics but this I'm a little puzzled any help would be good

I had a similar problem with mine (55 plate VRS). It started at around 40,000 miles, just a very occasional dribble from the expansion cap. With time and miles it got worse (never enough to bring the low coolant light on though), until I had to conclude that something was not right. I tried a new coolant cap, new thermostat and new water pump, none of which sorted it. Leak down test showed no issue with the head gasket.

Thing is that the leak down test is only carried out at relatively low pressure and running big load puts a lot of pressure into the cylinder. Upshot with mine was that it was the head gasket, which had de-laminated. Result was that the head and block where undamaged and a new gasket fixed it completely.

Only concern is that if the head or block are damaged, you will need to skim as little as possible from whichever face is damaged and then recess the valves back into the head by the same amount (the clearances really are that small).

Hope it turns out to be something else, but what you describe sound like the head gasket.

Chris