I was changing the rocker cover for BMW X3 2.0diesel but the timing has gone, How do I set it

Timing chain

if u have to ask you probably shouldn't go near it.there is nothing under there for a novice!
remove the filter ( 3 clips) from the back of the engine space
there are 5 (maybe 4) torex screws holding in the housing for the filter,remove housing
remove oil fill cap
loose cover should lift off
remove the 4 coil packs (they pull up off the spark plugs)
unscrew the 2 wires either side of the VVT motor
remove bolts(12mm socket) and rocker will pull off.
They can be a bi$ch to get back on.

make sure that the filler cap seal is in place and not gone hard over time also has the rocker cover been off at some stage if it has check that the gasket has not moved the other thing to look out for is that the PCV (breather )valve is in good working order if it is damaged the sump compression will rise and push oil out

Coolant temprature sensor? You should have it scaned to extract fault codes or you could get a sensor & try it 1st

The Rocker Cover Gasket creates an Oil tight seal between the rocker cover and the cylinder heads so that oil wont spill into the engine. There isnt a huge amount of work to replace one of these however a mechanic will still charge you between a hundered or two hundred dollars to replace it.

hi unfortunately there is no external marks to go by this is only achieved by removing the rocker covers and then putting it into top dead centre and seeing if the 2 camshaft marks align up at the top..

Injectors do not leak oil. they leak gas. If you are leaking oil then it is the rocker arm cover. replace the gasket easy to do. replace both because they come in a set.

are you sure its not getting hot? those engines came originaly equipped with a water pump that has a plastic impeller. the plastic would crack and be loose on the shaft it would still flow some water but not enough. i would have that checked out. i have changed many of thise pumps on bmw, volkswagon

once the valve cover has been removed you should be able to the nut on the side of the rocker. there is an eccentric that is adjustable with a special tool to assist you in turn the eccentric. im assuming you have some experience at this. if not get back with me and ill assist you better.

simple problem like misfire and the garage cant find it come on get the car out of there if everything was done properly and i dought that you need to check the compresion of the cylinder is bad chip valve bad ring one time i fix a sunfire the rocker came of open the valve cover check the rocker on the valve maybe one of if rocker of the comppression will show gone good spark gone injector let me know hope it help FIXYA OUR POST THANKS PIERRE