Hey all,

Before I get my turbo rebuilt on my 81 300SD (185,000 miles), I am going to do a compression test. There are a few things that I am not clear on that I hope you guys could help me out on, as always.

I do have some blow by, but I am thinking this is caused by the turbo which has a lot of shaft play and is leaking A LOT of oil.

If my compression test results are good, would I need to do a leak down test or should I only do a leak down test if my compression tests are bad?

What exactly is the benefit of a "wet" compression test, and could I use MMO instead of engine oil for a wet compression test and/or leak down test? I figured since I'll have the injectors out I could pour some MMO to clean the cylinders/pistons and free any stuck rings if there are any. Speaking of having the injectors out, I figured I'd replace the nozzles and get them pop tested, but that's a different topic .

I appreciate your input.