What in particular causes vacuum pump failure?
 

1984 300D with 197,000 miles showing on the odometer.
After reading all the awful stories about Vacuum pump failures causing timing chain failures I decided to pull mine off and check it (197,000 miles). Everything looked normal and there was nothing that looked at all worn .
I was wondering if anyone could tell me which of the parts inside the Vacuum pump is prone to failure?
Or, is it always that by the time the damage is over with there is now way to tell what failed?

There's a ball bearing that, in the earlier models, does not have a caged race. If the bearing comes apart, the balls and such can drop out and end up jammed in the timing chain, causing it to break. That stops the camshaft and leaves one or more valves open, which, since diesels are interference engines, causes one or more pistons to smash into the valves.

In the latest units, the ball bearing is sealed and should not be able to spill its guts into the engine. Apparently there's no way to tell when the bearing is ready to go.

Jeremy

There is a bushing on intermediate shaft which will ware causing lateral movement of the timing device (2+mms in my case) which took out my V/P. The bearing if the V/P that rides on the little "roller coaster" track of the timing device, can fail also.

Is this a problem on all 61x engines, just the turbos, or just some years? Seems like I haven't seen people with older (pre-w123) or non-turbo models report this problem.

Pump
 

My understanding is that it isn't so much the vacuum pump itself as the way the pump mates with the engine block and the casting holes in the latter that will allow parts to fall into the timing chain alley. The 603 appears to be most prone to this problem. I've hears of vacuum pumps failing on the 617 but apparently they are less likely to cause a failure of the engine itself. It's possible that the other 60x engines also have that risk -- but that is beyond my ability.

Jeremy

There is no side shields on the bearings in my Vacuum pump; you can see the ball bearings (car 1984).

intermediate shaft?
 

I am not sure which shaft you mean? I think there were 3 shafts:
1- The long bolt that goes through both sides of the housing and through the largest forked lever,
2- the shaft by the roller with tiny snap rings an
3-the shaft the roller rides on.
I looke but did not see any bushings. I will look closer the next time I remove it!
I forgot to say 84 300D turbo.
The only parts that looked delicate were those tiny snap rings.

The intermediate shaft is inside the timing device, you cant see it unless the T/D is removed. There is an exploded drawing in the Haynes manual that show the whole thin including the bushing which wears causing end play in the timing device, causing V/C failure. When the V/P is remover pull the timing device in and out to determan "end play"

Thanks. I got it the intermediate shaft is not in the vacuum pump. I have seen the pic in the manual.

Do you know what the Max. end play is?

I think its just age, with the 617 pumps. Nothing lasts forever, and at 300k miles it might not be a bad idea to put a new one on.

The 603 pumps were just a bad design, the new ones don't seem to fail.

Answer OM617 Turbo:
 

In order, the most common issues:

*****
#1. System vacuum leaks allowing dust and trash to enter the vacuum pump check valves.

*****
#2. Pump piston seal fails = allows engine oil to enter piston cylinder = oil coating check valves, system vacuum leaks allow dust and trash to build up on the oil coated check valves, eventually holding the valves open.

*****
#3. Incorrect rebuild, very common.

***
#4. System vacuum leaks allowing ABRASIVE dust and trash to enter the vacuum pump cylinder, scoring cylinder walls into junk = impossible to repair as a DIY = send in for rebuild or scrap it.

**
#5. Bearing or piston arm failure.





Have a great day.:)

I dont know, sorry, I would think, no more than 1mm, Anybody?

What sound does it make before failing?
 

I'm trying to track down the source of a light scratching sound coming from under the hood while the engine is running. I just replaced the alternator. I ruled out the ps pump by removing the belt. Does the vacuum pump make any type of sound when it begins to fail?

Pictures of 603 pumps
 

Hi,

I found a later pump in a trip to the wrecking yard and decided to use it to replace my older pump with unknown but probably very high mileage.

These pictures show the exposed bearings on the early pump that can fall into the engine upon failure.

http://www.crank-scrapers.com/VACUUM_PUMPS_603-A.jpg

http://www.crank-scrapers.com/VACUUM_PUMPS_603-B.jpg

http://www.crank-scrapers.com/VACUUM_PUMPS_603-C.jpg

http://www.crank-scrapers.com/VACUUM_PUMPS_603-D.jpg

The 617 pumps can fail. ON mine it did make noise and the vac system stopped working too before the pump came apart with catastrophic results. I heard the noise but when I took it to the dealer to hear it of course it miraculously healed itself. I knew something was up but had no clue such a catastrophic result was possible. The system went into comlete melt down on a trip to st louis halfway home and I was about 30 miles form home when it crapped.

That was fifteen years ago or more long before this excellent resource existed.

Tom W