Got a weird problem with my car

[RC18B 911 turbo]

Last week I topped up the coolant on my car as it was just below the min and about a week later it has gone way below the minimum mark and refuses to idle below 1100RPM also started to use up a lot of fuel but it has only happened recently like on my Journey back home today from Tiverton to Exeter which is about 40mins it was fine on the way up but not on the way back any ideas what this could be please?

 

[sawood12]

Head gasket? Could be loosing water through the cylinders which is why you don't have a puddle under the car. I'd get it checked out. If you leave the car standing for a long time so that water fills a cylinder and you try to start the car you will either break a con-rod or your starter motor. A work collegue was lucky and broke his starter motor.