Heres my story on my 80 300CD.

I can't blame my problem on Quickie-boob, so I try to sluff it off on the possibility that Wifie-poo may have called me in for lunch just about the time I was ready to tighten down the oil filter cap. Anyhoo...we had a bunch of oil spots all over the place and instead of really trying to find out where it was coming from, I just shrugged it off as a rear crank seal. I checked the oil before my daughter took off for a little shopping trip about forty miles north of here, if I had only started the engine with the hood up, I'm sure I would have seen the oil oozing out of the oil filter/cap.

So a few hours later she calls.."Daddy, my car quit running and its out of oil, the oil gauge says "zero"". When I got up there I filled it with oil, it was hard turning over until the frozen bearing gave up its "death grip" and then I found where the "leak" was. I tried driving it home but after a short distance I shut it down and went for a tow bar.

When I got into it, I found the number one rod had spun its bearing. so now the chase was on... What to do?? My three choices were;
Buy a used engine from a wrecking yard or private seller.
Buy a short block from a builder.
Do it myself.

I didn't like the idea of the wrecking yard option due to the fact that I'd have no idea who owned the car it came out of or what shape it would be in and who knows for sure how many miles it had on it.
I did find a late 70's 300D that a private guy had and went as far as loading it on the tow dolly, and while I was tying it down, that little voice in the background said "hey Quickie-boob type dummie...the a/c compressor is on the right side riding high and yours is the one hung low type on the left side". I had enough staring me in the face without having to reinvent the wheel too. So pass on that one.

I was about an inch away from the short block and someone told me that they really don't do that good of a job that they "run them through like a puppy mill". So what does that leave?? Yup.. do it myself.

About the second place I came across was a machine shop that specializes in crankshafts along with all the other automotive machine shop work. I bought a used crank that standard specs and was polishable. It was checked for plumb and straightened as needed then polished. At the same time I had new sleeves pressed into the block, thankfully the pistons were still within tolerances (whew..they were about $125 a pop and that was back in 1997). While all that was going on, I took all the rotating parts to the balancing shop for their tune-up, and the head went elsewhere.

This was my first time for anything with a Mercedes and I was amazed how everything fit like it really belonged there, no banging, hacking, or hot wrenching. It truly made a believer out of me.

I have a MB manual for the engine, but for me, it just isn't laid out or as systematic as it should be. Oh thank Heavens for the Haynes manual. It took me step by step, inch by inch, from one end to the other. Can't say enough about it.

The whole thing took me a couple of months of spare time and about $2000. I took a bunch of pictures before I started, so I'd be sure to get all the little stuff back where it belongs, also drew some pictures and made some notes, and still had to chase down another 300D to figure just how some of the last little things attached.

The two things that I didn't do that I kinda wish I woulda but fortunately haven't had any problems with, was replacing the timing chain (I think they weren't much more than $30 some bucks at the time) and the freeze plugs.

The crankshaft guy gave me a deep scowl and said "be sure to use Plastigauge.. don't trust anybody not even me..you've got too much into this". And when you stop to think about it..Sure thirty bucks here and forty bucks there starts adding up..but when you have that much of your time, effort and money into it...its really cheap. Like the old saying goes "There's not enough time to do it right the first time but always enough time to do it over again" You wouldn't believe how many places I went to trying to find the Plastigauge. Most didn't even know what it was, the others had a far away gleem in their eye "oh ya, I remember Plastigauge".

What you really have to do is weigh out how long you want to keep the car, is the rest of the car worth this?, could the money be put to better use by buying another car? In my case the car was near perfect on the outside with a few liveable problems on the inside. It had a $4800 paint job a couple of years before I got it. I'll have to admit, I didn't fall in love with it until I was half way into the rebuild. While it was down I bought a 90 190E 2.6 and thought it was the "Cats Meow", well when I got the job finished and back on the road, I kept stalling on trading back with my daughter and finally fessed up that I was keeping the 300CD for myself. So what happens?? In February I was sitting at a light minding my own business and was the front car of a four car rear-ender. The damage is only to the right rear fender and some of the frame along side the spare tire well. The insurance totaled it out at $5700 worth of damage. I bought it back hoping the Good Faeries might come one night and do a number on it but so far no luck. Theres about 35 or 40 thousand miles on the rebuild at this time and I've had the whole car up for sale for $1300. Right now my kid is using it while his truck gets fixed. I'd still hop in that car right now and head cross country in a minute.

I believe your engine is different in the fact that it has a hydraulic pump on it.

Good luck on whatever you choose to do, and if theres anything I can help you on just e-mail me.
Ernie