possible blown head gasket

hi there, I have a suspected blown head gasket on my 163K 1.9tD. Symptoms are: 1. Service December 2007 noted water in oil 2. For the last few weeks the interior heater kept blowing ice cold even after 20 minutes of idle 3. On Thursday night after extended idling in traffic then on parking, a considerable amount of cooling water shot out of the expansion chamber screw cap. 4. After it had cooled down i noticed the main (large) pipe from the top of the radiator to the engine was empty. 5. I topped up the expansion chamber but it would not filter into the radiator and the hose remained empty. I riskily drove it another 7 miles from, cold and it overflowed again. 6. The expansion chamber screw cap is oily inside and there are some oily scales in the escaped cooling water aroud the chamber cap. I picked it up from the mechanics today who had tightened the expansion chamber cap. They had run it and I noticed a small leak coming from the hose on the top of the radiator. I loosened it and let some air escape and inevitably some fluid dribbled over the radiator surface. The dipstick shows no sign of water ingress/froth in the oil. The temperature guage never goes above 1cm from bottom of cold stop. The radiator fan never comes on. The Engine sounds fine and there is no loss of power, nor smoking from the exhaust. Is there any way i can tell for sure if it's the head gasket? Could it be the thermostat or radiator fan? The mechanics seem a bit vague and say the only way to know is to drive it and see if it overheats. I just drove it a 20 miles round trip. I stopped midway and the radiator fan was not working and there was slight vapour from the surface of the radiator. I then turned the interior heating on full hot and when I checked at the end of the journey the radiator seemed hot but no vapour was wafting off its surface. The temperature seemed fine. Was it just an airlock? Cheers Dude

The best DIY test is to remove the expansion bottle cap when it's hot (carefully!!) and rev up. If the coolant volcanoes out, the gasket has gone.

You could test for hydrocarbons in the expansion tank. You haven't bothered to fill in your location, but Adamsky01 has just posted he has a testing kit (S Wales) A good local garage should have one as well.

i was going to say hydrocarbon test on the cooling system. also is the cooling system air tight ie holds presure as anouther way to see if compresion is getting into the cooling system is to depresurase the system cold put cap back on start up and feel the top hose to see if it gets very firm to press if it does you have direct bore to cooling system presure leek. also oil in water could be oil cooler on it esp if its a vw diesel in it. also bad water not circulating could be the water pump