I have a 84 300D with about 420k on it. I've been reading through a lot of posts with the vacuum pumps and I was just wondering if I should do a full overhaul?

Do you high mileage W123 owners replace the vacuum pump as a precaution? I don't want mine to go kaboom one day and mess up my chain etc. My vacuum pump is on it's way out.

At idle speed the system vacuum is not adequate to engage the door locks, nor shut down the engine. I have checked beyond the vacuum pump and all is well. The problem is my vacuum pump.

My question here is:
Do I just go ahead and purchase a “new” vacuum pump, or should I go the “rebuild” option?

I tend to lean toward the purchase a “new” vacuum pump, but I sure appreciate any input before I make a choice.

This is on my “fix list” for this summer. I value your input here.

Can you even still find rebuild kits?

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1981 240D 4sp manual. Ivory White.

Did you check how many inhg the pump produces by itself?

Even if it doesn't produce the proper vacuum it could be just a checkvalve that's broken.

Of course you want to inspect the bearings if you decide to go the rebuilt "route".

Checking the play on the timing device to engine block bushing is also not a bad idea when you have the pump out.

produces roughly 20 hg when it's working. However if I go on the highway at 60mph I will lose vacuum completely and brakes get hard.

I put in a check valve last year(found the old one collapsed inside) but no luck, the problem is still constant. When ever I lose vacuum I have to open the line up where it connects to the port and spray the check valve to get it working again.

I bought a rebuilt one last time. The remark on finding a rebuild kit is accurate. Mainly the bearing or pump arm. I think they are $180. I think the rebuilt one I bought was $300.

I did rebuild one myself. It was just seals. I do have a pump arm in new condition, somewhere.

Rebuild kits are becoming scarce and expensive and you don't know for sure that your pump can be built with the parts available. New Piersburg (OE manufacturer) pumps used to be available for less than MBZ wanted.

I couldn't find Piersburg the last time and bought MBZ. Hopefully, it will last as long as the car which will be until it is wrecked or fuel is no longer available.

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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.

This will give you a better idea of what the issue is:2 Vacuum Pumps destroyed timer Bushing Identified as the problem
http://www.mbca.org/forum/2013-12-29/why-are-these-vacuum-pumps-being-destroyed

The timer/front intermediate shaft bushing is the main exculpate in the vacuum pump failure that sometimes turns into the ruined engine.

On the older piston type vacuum pumps the bearings came with a plastic cage that eventually fell apart and caused the vacuum pump failure. Yours should be the updated one and not have that issue. You can remover your Vacuum Pump and take a look.

If you could find them there is 2 piston type vacuum pump rebuild kits. One has the stuff for the Piston and valves. The other has a new steel arm and bearing. The 2 of them together cost more then a rebuilt vacuum pump and the rebuilt will have a warranty and you get a new check valve with it (the price on the check valves has risen a lot).

A few people have converted to electric vacuum pumps but I have not followed that so cannot comment. I tried it and and it worked fine but the type of Vacuum Pump I used got really hot (it has a U-28 on it). I bought some other electric vacuum pumps and never followed through on it.

I am procrastinating on it but I am taking the Cylinder head off of my Mercedes and I plan to take the end play on the Timer/intermediate shaft to see if the bushing is worn out. I already bought a new bushing which was around $42. I will post a thread on the end play like 3-4 weeks from now.

This is from my notes. Any part numbers I supply should be re-checked:
0005891723 Piston Vacuum Pump Kit Piston end (Pierburg 4.05266.00.0)

Maybach and Meistersatz uses the same number as Mercedes) google search worked using this number only 000 586 17 23
Parts Interchange:
PIERBURG 405266500
MAYBACH 000 586 17 23
CARBUR... 051.904/00
MERCED... 000 586 17 23
PIERBURG 4.05266.50
PIERBURG 4.05266.00.0
PIERBURG 4.05266.00

The Pierburg and Meistersatz kits occasionly show up on US eBay and UK eBay.

I don't have a part number for the actuating arm end.

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84 300D, 82 Volvo 244Gl Diesel

If you are getting partial vacuum like the check valve is most often the issue. The Check Valve is built into the fitting tat screws into the Vacuum pump and the main vacuum line attaches to. Remove it look inside and see if the parts are still there.
If the parts are gone and have fallen inside don't worry about that there is another valve inside of the Pump that so far prevents the parts from moving further inside of the Pump.

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84 300D, 82 Volvo 244Gl Diesel

Swapped out the check valve in the vacuum pump last year with a new one from AutoHauz
. Today I just went out to the car opened up the line on the vacuum pump, put my finger over the check valve as the car waa running. I could feel vacuum but it was very low, so I sprayed some WD40 inside the check valve and I started hearing "pshhhhhh" "pshhhhh" vacuum came back to life.


This is a recurring procedure I always have to do to get the vacuum pump working. What could causing the vacuum pump to be going in and out like this?

Last time I saw a rebuild kit for the 1982-85 vacuum pumps, it was $110. That is just the teflon-leather piston seal, the internal check valves, and the silicone head gasket. You can source the check valves cheaper for a VW mechanical pump rebuild kit. The earlier 2-tube vacuum pumps have much cheaper rebuild kits (~10) which is mostly a rubber diaphragm. I think those will bolt to a 1982+ engine. But, a rebuild kit will not fix the engine threat, which is the roller bearing at the end of the plunger arm. The pump suddenly started making a tapping noise in my 1984 and by the time my son drove it home 150 miles, the arm had been worn half thru by dragging on the timing unit, since the bearing had failed. A little longer and the parts would have slid into the timing chain with likely bad results.

I have seen a replacement arm & bearings on ebay for ~$180 once. Last time I saw a new pump on ebay, it was $350. I don't know the status of the people who rigged an electric pump for a recent VW/M-B diesel. The concern is if the duty cycle will be too much, given the constant use by the VCV. Those pumps are intended to supply the vacuum booster. I have one, but haven't sourced a cheap vacuum switch yet.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

Electric vacuum pump conversion is good for manual or 79 and older automatics. They don't use vacuum for the transmission.

From 1980 the automatics use a VCV which will constantly bleed vacuum while you step on the throttle. As a result your vacuum pump will have to run all the time which will cause it to wear out/ make noise/ consume power

Are you referring to the external valve that can be removed without removing the pump?

Have you ever removed your pump to inspect?

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1981 240D 4sp manual. Ivory White.

Yeah that one. I havent removed the pump just yet

Many years back I had low vacuum and I removed the check valve and hosed it out with WD-40 and that restored it. However that is just a wild guess.

Find stretch's (formally called Army) thread on vacuum pumps. He has a pic of a piston type vacuum pump that he said the piston seal is worn out on. It had gunky oil through out the pump.
When I hosed out my Check Valve it had gunky oil in it.

Other then that I don't know.

Another though is if your crankcase gasses are not venting out well the Vacuum Pump is one of the places it might to. That could aid pushing oil into the Vacuum Pump innards.

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84 300D, 82 Volvo 244Gl Diesel

See post 12 for gunked up V Pump Pic.
http://www.peachparts.com/shopforum/diesel-discussion/338215-question-about-om61x-piston-vacuum-pump-parts.html

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84 300D, 82 Volvo 244Gl Diesel