Leaks in the climate control system can attribute to the harder shifting but not considerably. Yes, you could block that off temporarily to see if it helps the vacuum system work with your transmission. In fact, if you feel that all of the other issues may be sorted out, it might be the next step. If that resolves your shifting then you are looking at your next project.

Another hint that helped me was to purchase all new flex fittings (about $10) and just change them all out at once. This eliminated a lot of "ghost" leaks that seemed to be there one time and gone the next. One that definitely was defective was the flex portion at the tranny. It, along with that little cap, is in an environment that suffers a lot of abuse from oil leaks, etc..

Your climate control "defaults" to defrost with any failure, so that setting should always be operational.

These 20+ year old cars have quite a bit of rubber in their vacuum system and will take a little bit to resolve. But once you find the culprits for the leaks, you will be pleased with the results.

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Sam

84 300SD 350K+ miles ( Blue Belle )

It seems like I need to get under the car and see if the modulator is even hooked up. Before the green dashpot I have 22"hg, the line to the transmission doesn't hold any vacuum at all.

From what I can tell the systems are all set up to minimize interactions, but they do happen. Since I don't feel like pulling the dash apart to get the car to shift right, I was hoping that disconecting and plugging the vacuum lines to the climate control systems would help me get the car into a driveable state. As long as when it gets cold I would still be able to turn on the defroster.

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Chris

82 300SD

Once you resolve whether you have a disconnected vac. line down at the tranny modulator, then I would:
(1) Do like Sam [SD Blue] suggests and plug up the other vacuum user lines iith golf tees near where they come off the pump-to-booster main vacuum line... realizing that you will probably not be able to shut off the engine until you reconnect these !! This will also help to resolve the question of interactions too!
(2) While you are doing the above you can take your tiniest (sp?) drill bits and see if you can " gauge test " and clean out the restricted orifices that should be in the " T "s for these vacuum connections on the main vacuum pump-to-booster line. These should be only about 7 to 10 mm I.D. orifices. IF these have been drilled out to say 1/16 inch, then this is ~1.6mm which might very well contribute to interaction problem where other vacuum using systems cause the tranny to shift incorrectly.
On the run... in/out,
Sam

There is ample vacuum available to the vacuum control valve on the IP and the vacuum downstream of the orifice will not be affected by any leaks in the climate control system. Both systems are well isolated from the main vacuum system via small orifices.

To fix the climate control system and get things working other than defrost requires replacement of some of the vacuum pods that operate the vacuum doors. There is a troubleshooting procedure here somwhere regarding that..........or I can help you with it.

I'll look for that thread when I'm ready for that project, thanks.

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Chris

82 300SD

Today I got the car up safely, and took a look at the modulator, and hooked it up to the mityvac, and it is indeed bad. In fact it looks like there was a small amount of transmission fluid in the vacuum line going to the modulator. I'm pretty sure that is a bad sign too. There is supposed to be a little cap on the top of the green part too isn't there? There wasn't one on mine. I'm searching on how to remove it right now. I also looked at a Haynes Manual, which is only available for the w123 diesel, it makes no mention of vacuum at all.

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Chris

82 300SD

based especially upon your report of tranny fluid contamination inside the vacuum line. This is a fairly clear sign that the modulator diaphragm has failed. You did NOT clearly say it would NOT hold the vacuum!? The question remains as to just how far the fluid has been sucked into and contaminated the vacuum lines under the hood and possibly all the way to the engine driven vacuum pump.

As you replace the modulator [~$50 part]. Be sure that the short rubber hose at the modulator is in condition and " TIGHT ". Replace if there is any doubt as to the condition of this small rubber hose. Then start looking at the rest of the "engine vacuum" system and be wary of and look for signs of such tranny fluid contamination... and if found, maybe use a spray cleaner to clean things up a bit.

After the new modulator is in, then you want to get back to checking over the remainder of the engine vacuum situation... and to do this it is best to put a "T" on the line that runs down from the top of the engine to the vacuum modulator. Go back and see Brian's instructions. Basically there should be ~10 in of Hg vacuum at idle and this should gradually drop to a very low [if not zero] vacuum as you increase the throttle.

Keep on plugging and we will monitor and guide you along the way.

I have replaced my modulator and if I recall, it would be unlikely for tranny fluid to be in the vacuum line due to failure. When I took mine apart, that part seemed to be pretty durable. I would spray a little brake cleaner in the line, from above, and reattach it. Also, that little rubber cap (http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1VK0NC7XQ1W20O9J57&year=1982&make=MB&model=300-SD-002&category=J&part=AT+Modulator+Cap) provides a vacuum seal and the modulator will appear to be "bad" without it. I would pop a new cap on there and recheck with the vacuum pump.

After doing this, if it still appears to be bad only then would I change the modulator. I've been down this road and just trying to save you some excess work.

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Sam

84 300SD 350K+ miles ( Blue Belle )

I went to Plaza here in St. Louis, and got the new modulator. It looks a little different than the old one, but I talked to a tech there, and he said they had redesigned it. There is a plastic cap that goes on top now, and a black pin that goes, well I'm not sure where. I have read about this pin, but its not entirely clear where it goes. The adjustment is now done by a tiny plastic screw in the top, rather than the metal t-bar.

The transmission fluid appears to have only been sucked into the vacuum line that ascends from the transmission. I have thought about just replacing that line, with new and replacing the little rubber hose that connects the line to the modulator.

How does this thing come out anyway??

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Chris

82 300SD

Well, I think I just learned a lesson. I was attempting to get started when I put the T-30 head thing in the transmission drain plug, and it snapped off. Any ideas how to get that out?

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Chris

82 300SD

that you are talking about a medium size " Torqx " tool... and where you say "...it snapped off..." you are referring to the Torqx tool... right?

It it is the Torqx that broke, then you need to try and get something small enough and sharp enough to literally pick around the edges and try to pry it out.... that's my best advice without being able to see your predicament up close and personal.

Q - Can you get a digital "macro" up close photo?

Sam... Ross

Yes the torx head broke. Its actually countersunk so to speak in the drain plug, which didn't even budge in its hole. I actually had my camera out at the time, but in my irritation I put EVERYTHING away, and walked back to the O'Reily's where I bought them, and demanded a refund, and upgraded to a better one of the correct size.

My idea right now is to take a drill to the cheap torx head, and very gently break it up, and pull out the pieces, although that might cost me a new drain plug. Unless I go really berzerk (I won't), in which case I might need a new tranny.

I hope that gives you a better idea of what happened.

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Chris

82 300SD

My guess is that the tips of the cheap tool that broke is made of hard & fragile steel so drilling it will not be easy. Leave that as a desparate last choice to extricate the broken tip.

If you have a small center-punch, tri punching the broken off tip right in the center... and if you are lucky the proven fragile steel tip might just fracture again and then it will either fall out of its own accord or you can then "pick" it out. Even if the broken-off tipe does not shatter, hopefully you will make a good indentention that is centered for you to start drilling into. So try this first!
Sam... on the road in MS

Removal, replacement and adjustment is described in the link from MBZ.org that I provided earlier in the thread.

It is extremely important that the old modulator comes straight out with no rocking side-to-side or you run the risk of breaking off the plastic pin. If this happens, and you are very unfortunate, you will have to disassemble a portion of the tranny to remove the remains. Then you will have to return to the dealer and wait for the correct parts. (As I said, been there done that and am trying to save you a lot of grief.) Did you replace the black rubber cap??

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Sam

84 300SD 350K+ miles ( Blue Belle )

They are not available, since the new part comes with a little cap, I'm assuming that it is the replacement, however the new version of the modulator looks like it is sealed, and the cap is just to keep crud out of the little plastic adjustment screw. (You know the ones... tiny plastic screws that take tiny plastic screwdrivers, and break at the slightest hint of extra force.)

I'm not sure what performance products of fastlane have, but at Plaza Motors I got what I got, and I did ask if they were sure I had the right thing, because it looked different than what I had seen on my car. A tech walked in, and talked to the parts guy, and the tech said that yes, that they had redesigned it, but it will work just fine.

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Chris

82 300SD