Vacuum Pump, rebuild or replace - Mercedes-Benz Forum
 
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post #1 of 6 (permalink) Old 05-02-2016, 05:19 AM Thread Starter
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Vehicle: 1982 240D M/T 209,200 miles
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Vacuum Pump, rebuild or replace

Owner of a 1982 240D, 4-Speed Manual for 3 years. Mileage is 220K, 14K by me.

Troubleshooting has determined that my vacuum pump is weak. I can only obtain about 8” vacuum with the engine at cruising speed RPM.

The door locks work well, and the engine will shut down with this degraded vacuum (recently replaced the shutoff valve) when the engine is at cruising speed RPM.
I shouldn’t have to rev the engine to shut down the engine or engage the door locks.

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.

Thank you,
Carl
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post #2 of 6 (permalink) Old 05-02-2016, 12:10 PM
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With that year, you are likely to have the later style piston vacuum pump.

Rebuilding the piston pumps is more complicated, and more expensive, then the earlier diaphragm style.

For that reason alone, it is often better to just replace the pump. In addition, rebuilding the old pump will still leave you with a potential failure point in the bearing that rides on the cam gear. These bearings can fail and send steel balls in to your timing chain, leading to total engine failure.

That said, when doing your troubleshooting did you isolate the vacuum pump and run the car to test its actual output? If you did not totally isolate it you could have leaks elsewhere, like the brake booster.

Also note that on the piston pumps there is a check valve on the pump, between the pump and the main vacuum line. This check valve can fail or get gunked up and give similar symptoms as a bad pump. You could start by removing this check valve to inspect it, clean it, and see if that helps. I know that some have reported cleaning it once restored the function of the valve and it has been good for years since. Others reported taking the main line off and finding the check valve had come apart internally. If that is the case you can replace just the check valve - last I saw this was about an $80 part as opposed to the whole pump which is $300+.

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post #3 of 6 (permalink) Old 05-03-2016, 05:46 AM
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I'd check the check valves for oil and muck first. This can "easily" be done by plumbing in a vacuum tester at the pump outlet / pipe where there's nothing else but the pump fitted and see if that part of the system holds vacuum.

If you want too much information I've put up some information here

More than you are likely to ever want to know about OM61X piston vacuum pumps - PeachParts Mercedes ShopForum

1992 190E 1.8 <=>2.0 201.018 =>
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post #4 of 6 (permalink) Old 05-04-2016, 10:04 PM
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The Pierburg repair kit isn't much cheaper than buying a new one so I don't think it's worth the hassle.
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post #5 of 6 (permalink) Old 05-07-2016, 07:14 PM
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Quote:
Originally Posted by dmotoren View Post
The Pierburg repair kit isn't much cheaper than buying a new one so I don't think it's worth the hassle.
The copper impregnated PTFE ring for the piston is the "expensive" part in the kit (I don't really see why). The kits for the older pumps have the same check valves - if the check valves are the problem then this works out much cheaper than replacing the whole unit.

Flipping the piston sealing ring round sometimes helps (and also makes it a cheaper fix for a while).

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post #6 of 6 (permalink) Old 05-09-2016, 05:08 AM Thread Starter
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Thank you all for the helpful input.

Stretch, I have looked through "More than you are likely to ever want to know" information. Like a good Smörgåsbord, I'll find what is good!

uberwasser, thank you once again for your valued input.

dmotoren, I agree...it isn't worth the hassle

I am going to buy a NEW vacuum pump so I can move on.

Will keep the original and see what I can learn about rebuilding one with the hope of sharing some good information.

Damn these are nice cars!
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