Hey Guys, have an 87 300TD and have been replacing some of the vacuum lines. So far so good, but I've noticed that the PO seems to have cut and plugged the off-center line coming out of the top of the Blue Flying Saucer. My vacuum diagram seems to suggest this goes to the Vacuum Unit of the Auto Transmission (with damper), back into the car somewhere.

My question is, is this a known modification or should I try and restore this the way it was. My car takes a few seconds to shift when cold and still, but shifts fine when driving and warmed up. Any help appreciated, pics attached.

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I'd try to understand it more. Obviously the transmission is getting its vacuum from somewhere else, otherwise you'd have harsh shifts.

87 300 DSL auto trans shifting,,, slow to engage from standing start,, and flaring (slipping at shift points )... ? it's o to -5 C here and first drive my car seems to behave the same as yours,, fluid level normal , and changed trans filter and fluid in June,, dexron 3,, did not drain torque converter uhmm,,
will follow your responses,,added a photo of my eng bay,, I have no idea if PO has modded the vac lines,,shift problem seems to go away after 20 mins of driving,, but I'm not confident, the problem is gone ..

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I believe that pluged line goes to the vacuum pump.

You can eliminate the BFS for testing.

-J

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You're correct. That plugged-off connection should be connected to a hard plastic tube - black with a faint white stripe - with a couple short pieces of hose and one of the green plastic vacuum dampers. The black plastic tube with white stripe runs to the vacuum unit on the tranny. If you look at the BFS, that connection is labeled "TRA" for "transmission".

From this and your previous thread, looks like the PO did a lot of jury-rigging on this car.

In your first pic, I can see the tubing in question still running over into the vicinity of the BFS.

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Mitchell Oates
Mooresville, NC
'87 300D 212K miles
'87 300D 151K miles - R.I.P. 12/08
'05 Jeep Liberty CRD 67K miles
Grumpy Old Diesel Owners Club

Okay. Great. I've replaced a fair amount of the vacuum lines so far, and the thing is performing better all around. Is this something I can fix? Meaning, how hard to get to the vacuum unit on the tranny? I'd like to restore it to what it should be if I can.

It's just a matter of figuring out where the PO rerouted the hose. I doubt the hose was removed completely so it's probably floating around in the engine bay.

AH-HAH!! I see what he did now, after taking a closer look at your first pic.

Take a look at your first pic. Look at the main vacuum line running to your brake booster. The check valve that's in the line has a connection to supply vacuum to the ignition switch and thusly to the shutoff valve on the IP. That's the line that comes straight off the check valve, runs back over toward the BFS and then on up to the firewall if you follow it.

There's only supposed to be a single nipple on that brake booster check valve, with only the vacuum line running to your ignition switch attached to it.

He's added a tee connection onto that check valve. If you look closely, the short piece of rubber hose coming off the bottom connection of that tee is attached to the hard plastic tubing I mentioned before, black with faint white stripe, that runs to the tranny.

I'd opine that the other end of the tubing is still attached where it should be at the tranny - this type of jury-rigging, was probably too much trouble for the PO to crawl up under there and mess with it. That, and the fact the car still shifts somewhat normally - it wouldn't if the tranny were getting no vacuum whatsoever. At low speeds, that tranny would shift like there was a mule kicking the rear bumper with no vacuum (ask me how I know...).

That leads us to WHY the PO jury-rigged vacuum to the tranny in this fashion - seems to indicate that for some reason, with everything properly configured, the tranny wasn't getting vacuum or shifting hard.

#1 - Cracked vacuum line or vacuum leaks running to the BFS such that the BFS itself wasn't getting any vacuum.

#2 - The BFS itself has went south.

#3 - The Vacuum Control Valve (VCV) on the side of the IP - that supplies a variable vacuum signal to the BFS based on throttle position - is either misadjusted or has went south - that was the problem on my first 87 300D, the VCV had went bad altogether, no vacuum signal to the BFS.

#4 - Vacuum leak between the vacuum pump supply and the VCV and/or BFS.

I'd also suspect, from what I've seen so far, that the throttle cable and linkage, and the feedback cable to the tranny, aren't adjusted worth a crap either.

EDIT : Oops, I meant the FIRST pic - corrected above.

__________________
Just say "NO" to Ethanol - Drive Diesel

Mitchell Oates
Mooresville, NC
'87 300D 212K miles
'87 300D 151K miles - R.I.P. 12/08
'05 Jeep Liberty CRD 67K miles
Grumpy Old Diesel Owners Club

Hey Retmil46, I can't believe you deduced this from my pics, I had to go back and look at my engine to confirm. No doubt you're right, the T line feeds a line that goes back and down, I'm assuming to the tranny vacuum unit. I do have decent shifting after it warms up, so as someone suggested I must be getting vacuum from somewhere. I'm tempted to leave it as is for now, until I can find someone to properly adjust the linkages you pointed out were not well adjusted.

I recently replaced the vacuum pump to the new version that doesn't have the bearing failure issue, and so far things that need vacuum seem to be getting it. I was more worried that the BFS mod was cutting off vacuum to something I wasn't aware of, and even though I don't have the benefit of the BFS or dampener that used to be on that line, I think I can live with it. Thanks to you and everyone for all your advice on this, you guys are MB detectives.

Well, it helps when you've got an 87 300D sitting in the driveway, such all I had to do was pop the hood and compare against your pics.

Went thru pretty much what you're going thru with my first 87, as far as vacuum and tranny issues - although in my case, I was blessed with a PO that had kept everything stock and had made a serious attempt at maintenance.

If you can get ahold of a copy of the W124 Service Library, either download or on CD, under the engine section it has all the procedures for testing and adjusting the VCV, BFS, throttle cable and linkage, and feedback cable for the tranny. Believe me, it's not that hard - you could have all the above knocked out in an afternoon.

__________________
Just say "NO" to Ethanol - Drive Diesel

Mitchell Oates
Mooresville, NC
'87 300D 212K miles
'87 300D 151K miles - R.I.P. 12/08
'05 Jeep Liberty CRD 67K miles
Grumpy Old Diesel Owners Club

This might help you
Mercedes Benz Model 124 - OM606 Maintenance Manuals

Charlie

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Thanks guys, service manuals are on their way.