Dissappearing coolant

[Dave_M3]

After driving the car the water level is gone way down but it isnt overheating, Even if I fill it up completly it still ends up below the mark after running, Doesnt seem 2 be any leaks and the oil is fine, Any Ideas, I think it might be a cracked head

[Martinaston]

If its leaking into the oil it will be pretty evident because you would have gunk in the oil. If its leaking into the exhaust you will have steam coming out the exhaust and possibly pressure in the cooling system, try leaving it running with the filler cap off and see if it chucks the water out.

The other bits i can think of could be the heater matrix, try running it with the windows up on a cold night and see if the windows steam up, indicating a leak at the heater valve near the drivers knees.
Or a split in the pipe that feeds the matrix from the back of the head, difficult to see and normaly only visible from the steam rising or the water dripping down once the engine is turned off.

[Dave_M3]

Thanks 4 pointing out the possibilties, cos I was stumped, Ya the oil is perfect so at least My bottom end will be fine nd even if I do let it run with the cap off the water stays in so that rules out the headgasket I suppose, It could be the heater matrix but Theres no water evident inside the car and if it was leaking I'd say Id know cos Its taking well over a litre of water after driving 4 around 30mins. It runs fine so the only place where the head could be cracked is in the exhaust ports I suppose. I'll hav another look 4 those leaks going into the heater anyhow Hopefully might find sumthin

[Dave_M3]

Turns out it was a hloe in the top of the rad, Left it running on dry ground nd reved it up 2 warm it up nd discovered fresh water on the undertray and on the ground then looked trough the grill nd saw the water spraying out at the top. Cant believe I didnt see it before. At least its not the worst thing thats wrong I was convinced it was the head. Only a small problem now anyway. Thanks 4 the help all the same