Was having some high revs before the shifts on the auto transmission and some research led me to the vacuum system. After checking with a gauge I found the vac by the pump low and irregular. I pulled the vacuum check valve off the top of the pump and it seems pretty dirty inside. Is this worth cleaning or should it be replaced. There looks to be some damage to the threading at the top...also, can it be taken apart by bending the tabs at the bottom?

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Over 10 years ago I hosed mine out with WD-40 and things have been working normal ever since. Don't use brake cleaner as there is plastic parts inside and some plastics don't do well with brake cleaner.

The old one have been known to fall apart but the good news is there is a valve between there and the innards of the Vacuum Pump and no one has ever reported parts getting inside.

However, in a thread someone said the newer check valves are constructed differently so the part that fails the lower spring seat is different now.

Up to you on the replacement. You could clean it out and if it works drive the Car and order an new one but don't use it till the old one fails. If something happens to the Car before you need the new one you can sell off the new one you have not installed (note that the price on the check valves has gone up).

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84 300D, 82 Volvo 244Gl Diesel

Wow I finally looked at your picture. Yours looks different then either the new or old check valves I seen posted in the various Mercedes forums.

See the attached pic.

In any event it does not look like your check valve is going to be prone to falling apart as the old style ones did.

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84 300D, 82 Volvo 244Gl Diesel

On mine the sealing area is inside of the fitting. You can take a triangular file and straighten out the threads but what does the inside threads look like on the vacuum line?
If the inside threads on the vacuum line are stripped out/torn up you may need a new vacuum line.

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84 300D, 82 Volvo 244Gl Diesel

On mine the sealing area is inside of the fitting. You can take a triangular file and straighten out the threads but what does the inside threads look like on the vacuum line?
If the inside threads on the vacuum line are stripped out/torn up you may need a new vacuum line.

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84 300D, 82 Volvo 244Gl Diesel

Yes, it certainly doesn't look like any that I've seen online but it seems like a good design. I'm going to try to clean up the threads a bit and I hit it with WD-40. It looks like there may have been some sort of thread seal tape inside (no wonder it was terrible to remove). Did you put anything like thread lock back on or just put it back in? The inside threads on the vacuum line look fine.

I also just made a new discovery with the vacuum valve levers. One broken, one worn.

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You could put Loctite on the threads where it screws into the vacuum pump housing and that would help keep it from turning when you remove the Vacuum Line.
The Vacuum line seals inside of the fitting not on the threads but of course the threads have to be good enough tighten the line enough to seat it to seal.

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84 300D, 82 Volvo 244Gl Diesel

I thought those were for the EGR only. Someone correct if this is wrong.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

They used to sell the little levers as separate items. The worn levers can cause a vacuum leak in the valve/s.

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84 300D, 82 Volvo 244Gl Diesel

One is for the EGR, the other is to smooth up tranny shifting .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I just replaced both valve levers rather than bypass the EGR for the time being. I'm getting a reading (irregular/bouncing needle) before the VCV at about 16 and the line going to the modulator(after the VCV) at about 16 at idle, 5 at half throttle and 2 at full. It is also slow to build vacuum when initially starting the car. Suggestions?

It's time to settle in and begin testing the entire vacuul system, begin at the pump ~ you should have 20 + inches of vacuum from the pump within 30 seconds of start9ng the engine .

once that's done, begin checking each and every system for leaks, start with the brake booster , zero leak down is the key .

Once you get it sorted you'll be able to peak & tweak the adjustments to get proper shifting and so on then you can address the central locking, HVAC and so on .

None of this is difficult, it just takes time and working deliberately, not skipping any steps .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I went through the system and I've managed to get it functioning perfectly (except the leak in the door lock system which I've temporarily bypassed. Pressure at the modulator test port is spot on according to the specs. Unfortunately I still have flaring at the 1-2 and 3-4 on occasion even with the line to the modulator disconnected and an occasional hardshift down to first. I've read about replacing springs (K1/2 I believe) but I'm not sure I want to go down that path at the moment.