Originally Posted by ah-kay

This is my experience on the om603 engine. I don't think you have a crack head. Cracked head will overheat big time. This is what I would do. Need to determine the health of the engine in general.

1) run the car until the upper radiator hose is rock hard, making sure there is no overheating. If it doesn't get hard then the cooling system has a leak. Leave it overnight and squeeze it. If it is still rock hard then there may be a gasket leak.

2) remove all injectors and pop test them. Making sure the spray pattern and open pressure is ok.

3) check compression while engine still hot. However, I find hot and cold engine doesn't make a whole lot of difference.

4) turbo leaking oil will give white smoke. Lot and lot of it, like a chain smoking machine.

5) loud engine noise is subjective. Take the serpentine belt off and listen again.

6) check blowby by removing oil cap. You should feel cap is sucked in, a negative pressure vacuum feel caused by the turbo. If it is positive pressure then bad blowby.

Good luck.