Hello fellow W123 enthusiasts

[Deja Stu]

Just a shout out to my fellow W123 owners out there. I'm the new, proud owner of a 85 300TD wagon.Thank goodness I found this car before the prevous owner completely ruined it. I have several things to work out on it, and I am having a blast learning about, and working on this fine mechanical wonder. My biggest concern is the automatic transmission. When I bought the car, it wouldnt shift beyond second gear. The fluid was discolored, sort of brownish in color. Well now, after two fluid and filter changes, a new modulator valve, a new vacuum control valve and repairing some vacuum leaks it works fine "around town" but when I hit the highway, I can run at highway speed for up to 15 minutes or so before it completely looses 3/4 gear. It's just as if someone thru it in neutral, and I now only have 1 & 2 gear.I have to limp it home. When it cools off, it works fine again. I have been told the 3/4 clutchs in this 212K tranny are shot. anyone else seen this problem? Is there an experiment I can try to isolate the cause?Thanks for your time.

[VLayton]

That's a tough one. I'd say, not really. I don't advocate "experimental" additives but perhaps you can't go wrong. You've addressed many good issues already, and that's a new sypmtom to me. If the car was abused, that's probably it for the thing. I'd think the best way to go would be to use MB's transmission exchange program. I belive a factory rebuilt unit for a 617A engine is just over $2000 or so. (I've seen Honda trans rebuilds run $3400 on an Accord, so, a relative bargain)

If you're feeling experimental, I was told about a green transmission fluid that runs $15 a quart, called something like KDB or BSK: I can't recall, but this guy swore by it. Said it fixed every sick transmission he ever put it in, and immediately put it in every car he bought. Just heresay, it's an interesting thought.

Best of luck to you, keep her alive!

Vince

[Deja Stu]

Vince, thanks for the help. As for experimental ideas, what I ment to say was that I was told that prehaps I could place a vac gauge "in line" and monitor it as the temp. rose under the hood.Perhaps I have a vacuum leak that happens when a line or a union reachs a certain temperature. Another idea involves plugging the vacuum source to the transmission, and using a vacuum pump, (of the brake bleeder type?) to hold the vacuum in place while running at highway speed. The theory, again, being that I'm losing vacuum at a certain temperature.I'm inclined to agree that it may be done for, and it's time to exchange.I don't think the previous owner knew a thing about proper maintaince.That fluid looked "original"LOL. P.S. Vince I'm just 95 miles or so north of St. Louis, in west central Illinois, and would love to attend one of your future W123 "events", soon as this baby is highway worthy!How did the road adventure/rally go? did I miss it?I'm new to MBCA and just came on board the week of 3/28. Stuart

[VLayton]

Thanks for asking! I think it went really well, all things considered. I went on my first such "rally" for honeymoon 11/1/03. So I tried to create my own for my own little club's members. I did my best to plan ahead, and such a thing would never be flawless in operation, everyone expects that, and overall it was a pleasing sucess. I'll start a thread and report what it was like, ok?

I don't mean to sound stupid, but it seemed from your first post you would have covered this, but here goes anyway (because of your second post) At your point, I would test the trans vac line from the engine, and then the modulator if it leaks. If mod doesn't leak, test the line on a loop, replace all vacuum connections (loads of new bulk rubber vacuum connecting hose is a staple in my garage) if all that checks out, perhaps there is an issue with the transmission vacuum control valve mounted on the injection pump. I'm not sure how it works or how to tell if it's good, just how it's supposed to be hooked up. I've never replaced one, partly because they are $150 and partly I haven't found one that was obviously shot (that, I can discern)

If I remember, your said it was an '85? The trans kickdown control is a 3 prong plug on your valve cover. If it's a 80-84 there are one or more (usually 2 stacked on a pivot pin for a turbo) 3-way vacuum valves, which commonly deteriorate. About $45 each from your dealer, if yours aren't perfect, you'll see how the deterioration occurs.

You may know all that, but I spelled it out for those reading along

Cheers!

Hope that helps

Vince


PS, is trans shift linkage tight and aligned?

[Deja Stu]

Yes my linkage is good and tight, no problem there.I have tested the transmission vac line, it's good. I know the modulator is not leaking, it's new, and I replaced it's small connection line.This helped, as the old peice was hard, brittle and "fluted" at the ends. I also went over it and replaced a few other vacuum conections. I also have replaced the transmission vacuum control valve.I really think it's time to punt. As a side note, when I replaced the modulator, I knew nothing about setting the modulator pressure. I think it's on the high side, and has caused the transmission front seal to fail. Anyway, what I am seeing is a large increase in fluid loss since the modulator change. It's not leaking around the modulator, it is dry, so it looks like the tranny is going to have to come out, regardless. it's been a learning experence, and I have definitely made improvements. As I said, when I bought it, it wouldnt shift beyond 2ed gear. I could be content, and use it strictly as a town car, (as I said, it shifts fine around town) but I really want it to be highway worthy. Stu