1982 300D Vacuum Issues...I'm at a loss - PeachParts Mercedes-Benz Forum

GreaseDog · #1 06-27-2007, 01:44 PM

Thanks in advance for all the info I have gleaned from this board. I have a host of issues with 2 diesels right now, and I have been able to work through most of them with the info I have gotten from the DIY pages and searching the forum.

The cars are a 1982 300D and a 1982 300TD.

The vacuum system was pretty sound on the sedan with the exception of the door locks, but my vacuum woes have increased since I started working on the car. This is what I’ve done:

Removed the vacuum lines to the black box on the crankcase and removed the Tee’s and connected the lines directly to each other where needed as per Brian Carlton to bypass the EGR.

Cleaned out the banjo bolt and line to the ALDA.

Diesel Purge and valve adjustment.

The shifts were quite stiff, so I adjusted the modulator counter clockwise 2 clicks and got the vacuum to read 14” at idle down to 1” at full throttle while adjusting the VCV nut under the dome. It reads 6.5” at the 10mm span between the lever and the stop. A little tweaking on the Bowden and I have a car that shifts smooth and slightly firm only from first to second now. It feels great compared to the neck snapping experience before the adjustments. Thanks a million to all those that posted the procedures on this board.

Now for the odd stuff:

All the vents and CC were working properly, but now the center vents don’t work.

The car no longer shuts off properly. It slowly dies after turning the key off and takes about 4 seconds. I hooked my mighty vac to the shut off valve on the IP and when I drew vacuum the car shut right down. I don’t remember if it holds vacuum, but I will check today. The brown vacuum hose coming from the ignition switch to the IP is oily and leaking oil at the switch.

The door locks don’t work at all now, when before they were a little slow and after the car sat for a while wouldn’t work at all.

I know it’s a long post and I appreciate any input. My big concerns are the car not shutting off and the center vents not working when they did 2 days ago. I will get into the door lock system tomorrow. I was also wondering if while tweaking the tranny vacuum system and bypassing the EGR I may have affected the other systems in the car. I have re-checked vacuum connections and hose and tee integrity and don’t see any problems there, but will give the system another going over. Thanks Again.

dieseldan44 · #2 06-27-2007, 02:09 PM

Matt,

I have gone through a lot of this stuff.

Keep in mind the vacuum system is all interconnected. For everything to work right, every last leak has to be tracked down. Your transmission probably will flare badly as you fix other things since the vacuum level is raised. You need to isoloate the systems and then attack them one at a time.

You have a mity vac, right?

Pull and plug the lines from the master brake line the feed the shutoff and accessories. Get the transmission working right first, isolated from everything else.

-look in the Wiki DIY articles. Ive written an article on adjusting the modulator...do that first. get it to the right spot.
-now make sure the transmission vac is tight. Test the modulator, it should hold vac for 10 minutes or more.
-road test the car, and adjusting the VCV to achieve the right shifting.

-next, on to the shutoff. re-connect the shutoff and only the shutoff to the accessory line. try it - car may shut off normally. since there are leaks else where.

- add in the door locks. is that system tight on its own? test it with the mity vac. is the vac res holding vac well? get it figured out and put it in the system.

-then on the CC. i havent gotten here yet.

You have to add one thing at a time, or else its like trying to push down on a waterbed, something else will just get messed up.

good luck,
dd

GreaseDog · #3 06-27-2007, 03:32 PM

Thanks for the quick reply DieselDan. Yes I read you article on the modulator adjustment. It's a great DIY. Thanks for that one. I also read an earlier post of yours on replacing the modulator. I got a replacement for the wagon which is a 1982 300TD because it wasn't holding vacuum.

How did you get to those bolts that hold the plate on the modulator. Are they 10mm or hex bolts. I fooled around with it for about 10 minutes last night and was really frustrated trying to get to those bolts. I'll try again later.

Also I will take your advice and isolate each system to work on it. I'm off to go do some diesel work now and I'll let you know how it goes.

Thanks.

Shorebilly · #4 06-27-2007, 03:48 PM

Quote:

Originally Posted by GreaseDog

The car no longer shuts off properly. It slowly dies after turning the key off and takes about 4 seconds. I hooked my mighty vac to the shut off valve on the IP and when I drew vacuum the car shut right down. I don’t remember if it holds vacuum, but I will check today. The brown vacuum hose coming from the ignition switch to the IP is oily and leaking oil at the switch.

This is a sign that the diaphragm in the shutdown valve in the FIP is leaking...or was at one time...one never knows how far the previous owner and/or his mechanic went in a repair....but oil in the brown vacuum line is not good.....look at that shutdown valve again.....see if it holds vacuum and/or if it pulls lube oil from the FIP....if it appears to be good, perhaps it has been replaced in the past but the lines were not cleaned thoroughly...

SB

Most of us here have had vacuum problems at one time or another.....I know that I have a leak in my fresh air flap diaphragm....I will fix it sooner or later....

dieseldan44 · #5 06-27-2007, 04:00 PM

IIRC I needed a 1/4" ratchet and a universal. Its tight. I think they're hex...5mm rings a bell.

arew264 · #6 06-27-2007, 04:12 PM

YES, someone just posted about the one topic I'm really good at! (or at least I hope I'm good at it)

As DieselDan said, you want to get the tranny working right with everything else completely separated so's you can make sure it will operate properly when you eliminate the leakage.
It sounds like your shutoff is fine, with a little over 10", it should basically stop instantly.

That leaves the door locks and the ACC. First, the door locks (you want to attack the ACC last - it can be a pain).
The two door lock lines are yellow, and as DieselDan said, one is to a reservoir under the trunk (that lets your locks run after you turn off the engine), and one actually goes to the locks.
Make sure the reservoir holds. It will be very slow to evacuate, but should hold vacuum.
Next try to evacuate the door lock circuit. Try to get it to both lock and unlock, and find out if it is leaking while locking or unlocking or both. From there, you get to start pulling out floor mats (particularly the passenger one) to get to the vacuum lines. From there you get to start pulling apart doors to test and find which unit is leaking. With the floor mats removed, you can follow the lines and it should be fairly simple to trace the leak without just blindly pulling every door open.

Once you get the hang of this sort of thing, it gets easier.
Once you get all the leaks here taken care of, the ACC comes. There was a thread recently where I walked someone through it, and I'll try to dig it up.

The good news is that once you get the vacuum system whipped back into shape, you will basically have no problems with it for quite some time.

kerry · #7 06-27-2007, 04:31 PM

Push the far right button on the climate control, shutting it off completely. Then try shutting the car off. If it shuts off ok then, there's a leak in the climate control system, probably the center vent pod. It's a quick and easy way to isolate the climate control vacuum controls from the rest of the system for a quick test.

arew264 · #8 06-27-2007, 04:55 PM

Actually, the center vent pod not working is a symptom of leakage somewhere in the ACC system. It could be anywhere in there, and it doesnt have to be the center vent pod.

GreaseDog · #9 06-27-2007, 10:18 PM

Thanks for all the responses-I got a chance to do a little more work on my cars today. I pulled vacuum on the shut off valve on the 300D and got alot more oil in the line than vacuum. The vacuum bled right off. I guess it's to the pick n pull for another valve. I'd rather pay $20.00 for the new one from my usual online parts store, but they're on back order. This site sells 'em for $125, that's a little rich for my blood.
I'll take my chances at the boneyard, maybe I'll pull 2 just in case.
I'll tackle the door locks and the ACC tomorrow. I'll let you know how it goes.

Thanks Again.

kerry · #10 06-27-2007, 10:24 PM

Oil can also get into the system from the vacuum pump.

l76 · #11 06-29-2007, 04:22 PM

Sounds like a bad diaphram in vacuum pump. Oil in line definitely points that way.

dieseldan44 · #12 06-29-2007, 04:32 PM

Quote:

Originally Posted by GreaseDog

Thanks for all the responses-I got a chance to do a little more work on my cars today. I pulled vacuum on the shut off valve on the 300D and got alot more oil in the line than vacuum. The vacuum bled right off. I guess it's to the pick n pull for another valve. I'd rather pay $20.00 for the new one from my usual online parts store, but they're on back order. This site sells 'em for $125, that's a little rich for my blood.
I'll take my chances at the boneyard, maybe I'll pull 2 just in case.
I'll tackle the door locks and the ACC tomorrow. I'll let you know how it goes.

Thanks Again.

I think you have it right - shutoff valve. If the vacuum pump is bad the oil will originate from the master brake line.

rrgrassi · #13 06-29-2007, 04:37 PM

Get the engine oil cleaned out of the vacuum lines. It will damage the vacuum pods. also, make sure no oil is making it into the brake booster. Brake boosters have died from exposure to engine oil.

GreaseDog · #14 07-16-2007, 10:14 PM

Thanks for all the responses and help on this. I finally tracked down and fixed the problem. I pulled the ACC unit and the panel of switches on the console above it. I found an electrical connection had been pulled off of the center vent vacuum swtchover valve. Put it back on and all is well in the vacuum system. Car shuts off-center vents work and door locks etc. all functioning now.

Amazing how one little electrical connection can throw this whole car out of whack. As I get a deeper understanding of the vacuum system and get better at troubleshooting it, I find myself growing fonder and fonder of these little beasts.

Again thanks to everyone for the help.