'73 220D Vacuum Pump

[catfish]

Could a faulty vaccum pump cause abnormal, excessive smoking?

[redghost]

It could. Mostly involved with timing of fuel, so I would not be sure what all the vac does in your car other than lock and things. I have a flap in the intake the vac regulates, but nothing else. The IP is chain driven and most smoke in these old cars is unburnt fuel, so delivering bad fuel or too much to burn completely.

[pch2021]

actually, a bad vacuum pump is more often a cuase of smoking and oil consumption.

this is usually caused by a diaphragm inside the vacuum pump [$12.00] that tears, and allows oil from the pump to be sucke dinto the intake manifold. It is a fairly simple part to chjange. you will need a 19mm line wrench and a number 5 flathead screw bit with a small wratchet[ no screw drivers- these are soft screws].

remove the enginte cover [all 8 screws] on the face of the vacuum pump, plus the two lines. Don't touych the valve assembl;ies on the front. the diapragm is secured with a 5 mm allen bolt.


a more serious issue COULD be the injection pump diaphragm. For this repaiur it is HIGHLY advised that the pump be removed, retimed, and the diapragm [made of leather] replaced, whiuch can be tricky, as placing the shims is quite hard. I have had to do this only twice so far, and it is not fun.

the way to test this item is to a] get the car up to 50 mph, and left go of the accelerator.

if you see excessive white smoke, and the vacuum pump is ok, then you, my friend, need an IP diapragm.

perform said test, but first, remove the line from the vacuum pump to the intake. if there is oil in it, your diaphragm is bad. change it, and dont wait.

[catfish]

i feel like a dumb*** now that i have two threads associated with my car. when i get the car back from the monkeys around the corner, i will replace and test as you recommend.

[pch2021]

its fine- just remeber: your 220D[ or anyone's] is an automotive anomaly- most newer Mechanics just "don't get it".

many assume that these cars will need "rebuilds" on their engines due to small jobs that could tkae about 5-10 hours, tops. In my opinion, if it runs, you don't need to tear it apart. I love Mechanics who say "the miles are getting up there", then, who rebuild the motor, only to have it run worse than it did before. this happens far too often with the 220D's.

[catfish]

to what torque settings would you replace the screws, with ratchet, of course. i would hate to strip these buggers...

[catfish]

what does the vacuum pump run off of? how does it operate?

[redghost]

Pierre will know for sure, but I think it runs off the crank and a little plunger (more like elbow) moves a rubber diaphram back and forth like a bellows

[pch2021]

you go it, clay. it runs off the timing gear [in front of the injection pump] with a piston that moves a diapragm back and forth. The vacuum system really "aplifdies" intkae vacuum on the 115's, helping the intkae draw air in, as well as helping the vacuum system retain a constant draw. Pistons RARELY fail. Diapragm failure should be expected.

[catfish]

i will rebuild the vacuum pump if not only because i'll have it apart and accessible and the parts are cheaply obtained. will the oil need to be drained from the engine?

pierre; why do you recommend pulling the injection pump to change the diaphragm? from the manual (pg07.1-215) it seems as though the diaphragm is readily accessible. and i do not doubt that removing the injection pump would be difficult!

[catfish]

should the vacuum pump be removed from the car to replace the diphragm? it appears it can be replaced without taking the pump out, but i do not know if the allen bolt is under load and the plunger will pull back when it is removed...

[pch2021]

see, now you're cutting corners.

The diaphagm is VERY hard to change. it has a number of shims that are EXTREMELY hard to replace. even on a bench the diaphargm is difficult to install!

the other issue is that by the time the diaphragm is worn out, the engine will almost certianly need to ahve the pump retimed, via the timning gear [not moving the pump forward]. You might acgtually want to attain some factory MB text book literature.

the vacuum pump DOES NOT require a rebuild if the diaphragm is toern! You are overcomplicating things. Changing that diaphragm is neccesary- rebuilding the pump is not. stick with my advice, please . I work on 115 diesels day in and day out and i am saving you a few headaches.

also, give yourself PLENTY of room to work, and tkae care and buy the right tools for each job.

i.e. for the vacuum pump repair, remove the fan and shroud.

[catfish]

i have the valve portion of the vacuum pump removed, and i have the allen bolt about 3/4 of the way out, while holding the 1st washer steady (has two little holes and i made a tool to hold them). the allen bolt doesn't seem to back out all the way and feels as though it is under resistance. i think there is a spring behind it (according to the manual)? it should back out all the way without hassle, correct?

sorry if i offended your advice. i thank you for it and appreciate it greatly. the diaphragm came with a little document that states the pump should be removed, so i am asking the expert :)

[catfish]

the above parts needed to do the maintenance are on their way. looking through the bio-diesel archives, some say to replace the cigar hose (fuel returnline) and others say this is a bad idea because it contains magical powers. which is true? i have a replacement bio-friendly hose in hand. possibly, i will install a new MB cigar hose instead...

[catfish]

there i go, confusing my two ill-placed posts. sorry to get two issues intertwined guys... the above is in relation to the B100 thread.

[pch2021]

its fine. cody(:

we like you!!


there is no spring behind it. just keep removing the the 8 screws. do not touch the valve! you dont need to. i'll post pictures soon- i need to change the smae item on my '73 220D!

[catfish]

i rebuilt the vacuum pump's upper half. everything went smoothly, actually. the inside of the upper half was covered in oil; i could pour it out! i replaced both valves and the parallelagram gasket. when i installaed the diaphragm i used some locktite to keep everything where i put it. the old diaphagm wasn't beat up as i thought it would be. it isn't getting oil in the intake, so far...

it still puffs away. i will let her break in the new pump and give it a week. she is sounding a lot more like the 300D down the street. but that one covets the class of my ride. on a sadder note i bought four glowplugs based on a recommended part number, and should've ordered the pencil style plugs instead of the loops. always pull the part!

[captpk]

"replaced, which can be tricky, as placing the shims is quite hard. I have had to do this only twice so far, and it is not fun."

I am changing the diaphragm on my 220D and have a repair kit that gave me the new diaphragm, allen bolt, and two random screws. There are no holes in the diaphragm where the rivets on the old one go to. Does this mean that I should tap the holes and use the screws to put the shims back on. That leads me to the next question ... how do I put the shims back on after drilling out the rivets (should I even do that ... or order new shims?)?

Last question ... is it absolutely imperative to re-time the chain ... and is that hard to do?

thanks.

[redghost]

Has your timing gone out? Usually you can just measure to see how much stretch you have. if it is horrid, you should change the chain out and it should go back to being a well timed engine.

[Laser Beanz]

Captpk: without actually seeing the diaphragm you're working with I'm not certain mine is the same as yours, but when I first encountered it I had the same exact thoughts you described.

I just rebuilt the vacuum pump on my 1970 220D, which is probably fairly similar to yours - I know the 1968-72 W115's are mostly identical but they may have changed the vac pump in '73, I'm not sure. When I got the old diaphragm out it was sandwiched between two round metal disks (maybe these are the "shims" you described?) and the hexagonal bolt went through the center of these. The disks had a pair of small round indentations in them that made them appear to be pressed together permanently; however I pried them apart (they were pressed together really tight) and there were no connecting screws or anything else, the tension of the hex bolt when it was tightened kept them in place. Everything went back together fine; the two extra screws were identical to the ones that go around the perimeter of the diaphragm & I think they are just extras. The only difficulty is keeping the diaphragm from twisting while tightening the hex bolt because the discs gripping the diaphragm want to turn with the bolt.

Again, I don't know if this is what you're seeing on yours but it sounds familiar. Hope this helps!