I have a 2002 Astra 1.7 dti - 128k miles. Its losing a lot of coolant each day - 4 litres in 120 miles. Not losing anything whilst sitting still - only when being driven.
There are no visible signs of leaks - even had it to a mechanic who is stumped. It's been happening for a week - only other sympton is that its also getting harder to turn the engine over when cold (2 occasions - yesterday and today).Any idea's?

Jim, March 2009

The system is pressurising. Also noticed today large plume of white smoke, possibly steam from exhaust when engine had been switched off and then restarted after 5 minutes.
Thanks for your replies so far.

Jim, March 2009

also in addition to the last answer it may not pressurise if the injector tube seals have failed /the seals and the tubes rot away and can leak coolant into the injector ports in the cylinder head /get your mechanic to perform a cooling system pressure test if it looses pressure then you will need to get the cylinder head removed to correct the fault

gtwannabe, March 2009

poss be head gasket or cyl head cracked- is expansion tank pressurising ? water is probably entering bore/s when stopped due to cooling system pressure which will cause it to "hydraulic" when next started ,

k, March 2009