Hi everyone, i need your extensive help on my astra 1.4 I notice from today after checking my water tank that there was no water at all so i refilled it and afer 30-45miles drive the engine block light(ECU) showed up, stays a while and goes off and later stayed untill i switched the engine off. i tried driving on the motor way with the car at neutral position and the light went off and when i changed to 5th gear the light went back on.
What might be the possible cause please experts?

Arasraa, February 2008

Check the oil, if it's whitish or creamy colour. Stop driving the car, you've probably got an head gasket blown, and the oil and water are mixing. The engine would run very hot! the more you drive it the more gunge you're sending around the engine. An expensive job to clean up.
Check the water expansion tank, if there's globules of oil in it, you've got the same problem as above. A garage can test this using a probe, you can't always see this problem.
If you've recently messed with the water in the rad, there might be an air bubble in the system, you'll have to bleed the system to get rid of it.
Driving the car in or out of gear has no effect on the water problem. However good luck, come back to this site to ask for more info if you need it.

Ray Carcel, February 2008