Hello all,

I am really liking the forum. I am new but everyone is offering kind words. I recently posted about a IP but I have put that idea on the back burner for now because I have discovered an issue that I would like to get around to first so here goes:

I recently purchased a 1991 Mercedes Benz 300D 2.5 Turbo. I bought it because of the condition of the car and the hundreds (literally) of service records. This turbo diesel Mercedes has 331,298 miles on it which is kind of worrying me about the problem.

The engine (OM602) works just fine but I am having issues on this horrible banging noise (almost feels and sounds like I'm being rear ended pretty hard) downshifting and even upshifting. I have looked for a while tonight and have discovered the Bowden cable adjustment method and the vacuum modulator (I have yet to spot this). On the other hand, I have leakage it looks like coming from the transmission dropping off bolts from the oil pan and other places, although it's not much leakage at all it still concerns me.

I am worried the tranny is failing due to the hard shifting and the transmission (yes the discharge is red fluid) from the bolts from the transmission ( it doesn't look as if it is leaking from the housing unit internal on the transmission so I am hoping it's not anything worse than a seal leak.

But I have discovered a video that describes how to adjust the Bowden cable but unfortunately on my OM602 the adjustment but is not present at all that I can see. I was reading through and someone had implied that the OM602 engines have to be adjusted at the throttle linkage. Is this true? And if so, how would I go about doing that procedure. Thanks in advance.

STÜDZCUSTOMZ

If your tranny is like my 1981 300SD, you have vac problems. The tranny bleeds off vac for upshift and needs good vac for downshift. Sounds like your problems are at least vac related.

Find or buy a Mityvac and chase down your vac leaks for a starter. There are a lot of threads in the forum about this.

X2 on vacuum. Any time I have had hard shifting issues on my 91 (or the 92 I used to own) it has been a vacuum leak.

The vacuum system is going to be very tired after so many years and miles. One of the advantages of doing the wastegate swap (do a search) is that you are able to eliminate much of the vacuum routing....fewer vacuum lines means fewer opportunities for leaks.

__________________
14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife