Car has been running absolutly fine and then last monday the coolant warning came on the dashborad. Checked the coolant level and it was below full but above minimum. Restarted car and no warnings to be seen. Then everytime i started the car cold the warning came on, if i restarted once warm the warning went away. I read on here about the senors getting corroded etc so had a go at cleaning these etc. Last thursday was doing a long trip so thought id just check the oil and water before i went, i noticed what looked like dirt in the water but the levels were okay.

Well the long trip went without problem, car enver missed a beat but the coolant warning never went off regardless of the engne being warm or cold. On monday when i opened the bonnet to again try and find what the problem was i noticed the water tank was no longer clear but black. It is now complety full of oil, which even my poor mechanical head is a bad thing.

Any ideas? Will it be the head gasket thats gone or maybe the oil cooler thats failed? The car runs fine, no white steam/smoke, no issues starting it, no over heating, heaters work as they always have so im not sure its a head gasket failure but not too sure what else can mix the oil into the water and not cause many other problems.

I had the car delivered to a garage by the RAC, now just waiting to see what they say is wrong with it.

Oh and the car is an 08 PD170 Octavia vRS

Oil cooler is certainly an issue, but I have to say that it's worth them running a test for exhaust products in the coolant.

If they're there, then it'll be an HG failure IMHO. I wouldn't want to rule either out. Not much help I know.

The coolant light can come on if there is crud over the sensor in the tank, so perhaps there was enough light oil contamination that the prongs were coated and reading an issue, then the dump of oil came on the longer trip as everything warmed up.

Yep oil cooler went on mine , and with the same symptoms !