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I think my vacuum pump is failing

10K views 38 replies 7 participants last post by  PlaneCrazy 
#1 ·
Hi guys I think my vacuum pump on 1984 300D Turbo Diesel broke down although it is still producing vacuum. Please take a look at my video of testing vacuum pump with vacuum tester. Is this what's called 'erratic needle'? Also I noticed oil inside vacuum pump line as shown in the picture. What would be cheapest way to address the problem? Thanks!!!
 

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#3 ·
It is difficult to tell you the cheapest way to fix a problem without inspecting the internal components of the vacuum pump first. You have to pull it out and see what is wrong inside the pump before deciding what to do, but you have to do it as soon as possible before it fails completely.
 
#4 ·
Thanks luisg92, I have decided to get used vacuum pump, overhaul it and install. Then overhaul my own pump and keep it as the spare. It is going to be pricey, but it looks like these pumps are getting scarce by the hour and I intend to keep my Benz for a long time.
 
#6 ·
A bouncing needle could be lots of things (that probably aren't worth going into at the moment). The biggest concerns I'd have are the oil in the lines and if the intermediate bushing on the timing device is out of spec. This bushing takes a pounding and when worn allows a great amount of movement which knackers vacuum pumps. So when you remove the existing pump check the play on the bushing by pushing the timing device. If you think (just think) there might be some play it is best to make a decent measurement with a DTI / clock gauge
 
#7 ·
Thank you, Stretch for your comment. I do appreciate it. I am very new to these things and over weekend I am going to try to figure out the structure and operation of vacuum pump. I will follow your advice too. I am going to remove vacuum pump sometime this weekend and inspect it and take some photos as well.

I need to clarify one thing. Basically you are saying that there's bushing on the timing device that does not allow oil to enter interior of the vacuum pump where the bearing / lever / coils / piston are?

Also if you have time, can you please elaborate on DTI / clock gauge comment, because I am not familiar with it at all.

Thanks agan!
 
#8 ·
...
I need to clarify one thing. Basically you are saying that there's bushing on the timing device that does not allow oil to enter interior of the vacuum pump where the bearing / lever / coils / piston are?

Also if you have time, can you please elaborate on DTI / clock gauge comment, because I am not familiar with it at all.

Thanks agan!
The bushing on the inner surface of the timing device is the part that helps the timing device to turn

(Aside: the timing device is a little bit like the advance retard mechanism of a spark ignition engine - only because this is a diesel the time at which fuel is injected into the cylinder needs to be changed for different engine speeds)

The timing device is a big lump of metal that is attached to the intermediate shaft which is then connected to the injector pump. Because the vacuum pump runs on a "roller coaster" track to make a reciprocal motion there's a fair amount of "force on" / "force off" pounding going on. This pounding wears out the bushing. If the bushing has too much play in it then the pump's lifespan is seriously reduced.

I wrote a whole load of stuff about piston vacuum pumps a few years back here =>

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

Bit over the top (looking back now) but scan through and you'll see a DTI / clock gauge

####

As for oil sealing - well there's a seal on the piston pump's piston but this often allows oil into the other side which can make its way through the non return valves and creep into the vacuum tubing. When this happens it is definitely time for inspection and a bit of a clean.
 
#11 ·
Hi Stretch!

So I decided to pull vacuum pump off the engine to inspect before buying new pump / any parts / kits, etc. The engine has 130000 miles on it. Upon inspection everything looked OK and was super tight. Lever wouldn't budge. Bearing was spinning without an effort and did not make any noises. Rocking, pushing, pulling timing device showed no play whatsoever. Valves had crude on them and rubber washers were a little stiffer but still quite flexible. Main check valve had oil residue inside and some debree. I washed valves in lighter fluid and blew through them -- they were only letting air one way. Below are the pictures of what my pump looked like when I opened it up.

I cleaned the pump and put everything back together and reinstalled it on the engine with a new gasket. I decided that the pump wasn't failing and I will need an overhaul kit -- valves, gaskets, o-ring. Next time I won't be removing the pump. I will just unscrew the cover to replace valves / gaskets / pull piston and inspect piston liner and o-ring.

Tomorrow I am going to re-check vacuum to see if the needle stops bouncing.

Any thoughts? Suggestions? Maybe you will see in the pictures something I am not aware of? Does oil covered interior of my vacuum pump look as it should? Thanks again! Very much appreciate your input!

Alecs
 

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#12 ·
I am pleased to report that after removing vacuum pump from the vehicle, inspecting it (everything looked good and tight), washing 3 valves + main check valve in lighter fluid, reassembling it and installing it back on the vehicle I am getting steady 22 in Hg of vacuum. Ling to the video is below. I am wondering is there any place to buy just the complex shaped o-ring that goes under vacuum pump gasket?

 
#14 ·
I am pleased to report that after removing vacuum pump from the vehicle, inspecting it (everything looked good and tight), washing 3 valves + main check valve in lighter fluid, reassembling it and installing it back on the vehicle I am getting steady 22 in Hg of vacuum. Ling to the video is below. I am wondering is there any place to buy just the complex shaped o-ring that goes under vacuum pump gasket?

https://www.youtube.com/watch?v=qiqliS3lDOw&feature=youtu.be
The o rings seem to be only available in the repair kits. The cheapest solution was to buy just the O ring and the non return valve kit for the earlier diaphragm kit as these are also used in both pump types. The Piston pump repair kit was way more expensive last time I looked.

I'm glad to see you've got a good result after the cleaning - it is amazing what a bit of cleaning can do for things.

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I hope you used the correct gasket between the pump and the engine block - that dimension (gasket thickness) is critical to vacuum pump life expectancy!
 
#13 ·
Hi Stretch,

I was wondering if I could pick your brain one more time? I think that oil inside brake booster servo line comes from somewhere else, not from vacuum pump. The other end of booster servo line that attaches to booster is dry and oil free. Is this possible oil comes from somewhere else?

I know my car had recently had massive oil leak inside passenger compartment as I found residues of oil on the driver side front floor under sound dampening material. Is this possible it is related to oil traces I found inside brake booster servo line? Take a look at the picture please and that you very much!

Alecs
 

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#15 ·
I don't quite follow what you mean.

The picture seems to show oil in the brake booster line connection (!)

The hard line that is undone should go to the top of the vacuum pump right?
 
#16 ·
Hi Stretch! There is metal line that connects to vacuum pump check valve. There is traces of oil in this metal line. Booster line connects to this metal line. At the connection there is traces of oil as shown in the picture. The other end of booster line connecting to brake booster is dry and shows no presence of oil. Booster line also has couple of valves and vacuum lines attached. My question is if there is traces of oil in booster line does it always come from the vacuum pump?
 
#18 ·
I can't think of any other way for black engine oil to get into the system - if you were unlucky (very rare) you might get transmission oil sucked up from a transmission dashpot if fitted. But that's a different colour - and you'd see that first coming up from the other side of the engine.

There's a little non return valve before the brake booster that is probably stopping the black engine oil from getting any further for the moment.
 
#17 ·
Yes, vacuum pump availability is a concern. It seems there are not that many pumps available and rebuilt ones are way too expensive. I tried to get several sellers on e-bay to describe condition of their items to me, and they wouldn't even get back to me. I am relieved I did not have to spend $$ on the pump or rebuild kit as I needed funds for the next series of repairs -- replacing A/C compressor, vacuum system overhaul and a never ending war on rust.

When I put the vacuum pump back I used VictorReinz OEM - Vacuum Pump Gasket 6160110380 from autohausaz.

Thanks again for all your input!!!
Alecs
 
#22 ·
Fellows,


New Vacuum pumps are still available from the Classic Center in California. I just purchased one today. Details are the following:

000-230-13-65 Pump

List $420.00


616-011-03-80 gasket

List $1.90


Regards,

Angelo
 
#26 ·
Its a vacuum pump. Air only flows towards the pump, oil cannot get into the vacuum system from a failed vacuum pump.
The only source for black oil is the engine shutoff actuator and red oil is the transmission modulator.
 
#27 ·
That is indeed how things should be when the pump is in operation.

Unfortunately it isn't always like that. These piston pumps are connected to the crankcase where the main moving parts are splash lubricated with engine oil. The piston seal is not perfect and engine oil makes its way to the other side of the piston where the vacuum is made. Eventually, over time there is a build up of oil / muck on the inside of the vacuum pump which can lead to the non return valves not working as they should.

In short the pump workings get dirty and oil makes its way into other parts of the vacuum system in this way. Once the pump stops working, the travel of engine oil is encouraged by the presence of vacuum: On one side of the piston you have atmospheric pressure + crank case pressure. On the other side of the piston you have atmospheric pressure - (minus) the vacuum induced pressure from the pump. There is "encouragement" within the system to draw oil past dirty / worn parts in the pump into the clear vacuum line.
 
#32 ·
OK,

So I pulled a plastic vacuum line off a shut off valve, and inspected it. Unfortunately my observations inconclusive. First of all there is gunked up black oil right on the edge of the plastic tube. At the same time this plastic tube appears to be dry and clean and free of black engine oil on the inside. So my guess either the oil came from the outside source -- maybe like oil filter housing, or my car may have had a dramatic event in its past that is been taken care of and cleaned up.

Then I hooked up vacuum tester and tested shut off valve. It did lose vacuum albeit at a very, very slow rate. Because it was loosing vacuum so slow I thought maybe it is due to cracked up rubber fitting. Can someone suggest where to buy a new rubber fitting for shut off valve and what size/diameter to buy?

Thanks!!!
 

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#35 ·
I think there's a limit for the amount the vacuum system is "allowed to leak" in the FSM. Certainly for the brake booster - probably for the rest of the system too.

As for the size of the lines - measure them! (Sorry couldn't resist!) - you can buy the replacements at the dealership and at the better stocked automotive parts stores.
 
#37 ·
If you want part numbers it is best to go and look through the stripped down EPC on the MB Atlanta site. The cost of this pipework at the dealership, however, is pretty steep.

Here are some part numbers to get you going =>

1162701247
1162760630
1232761930
1232761630

(This isn't an exhaustive list - I think there are several more)

But like I say I reckon you can get as good for cheaper elsewhere - the price at the dealership is usually per meter and not necessarily at a length that you need...
 
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