240d compression

[stuarth]

I have a 240d from 1982. 120k kms from new. It is low on power and my garage tells me the compression is low on three cylinders. Seems odd since I had a test 4000kms ago and it was ok.
So, it could be, I guess, head gasket, valves or rings. First, am I right and second, what is the most likely of these? And third, valves and headgasket are easy but rings? I have never done them - do I need to remove the engine if it is this? Any way of further testing?
Thanks for any advice

 

[Tinkerer]

Don't know if it works on a diesel but on a petrol the difference between a wet & dry compression test tells you if it is rings or valves. Head gasket usually has other symptoms, blows out water, blows water into oil & vice versa sometimes just between cylinders. Anyway you will have to have the head off to do the rings and also the sump, if you can get the sump off by just (joke) lifting the engine you might be able to do it in the car.

They say that necessity is the mother of invention .

 

[Number_Cruncher]

Check the valve clearances.