I bought a second hand corsa a few weeks back. After a week the engine blew due to no water ive replaced the engine with a new one as i really like the car. The issue is it still loosing water the garage has had it and says its something to do with the pressure. Whats happening is after Ive driven the car and i park up and turn off the engine the water bubbles up and overflows out the water expansion tank. (I think thats what its called). Ive ordered a new cap just incase thats damaged as the spring looks abit dodgy to me. Every car Ive had has always made a hissing sound due to the release of the pressure this dosent hence im getting the cap just incase.

First the garage said it was the water pump but when they went to replace it said it wasnt so didnt replace it. He has said its not the head gasket.

The engine management light is on but my mechanic has said he has had it on the diagnostics and there is no fault coming back.

If anyone could help it would be much appreciated.

Thanks in advance

Allison