What in particular causes vacuum pump failure? - PeachParts Mercedes-Benz Forum

Jeremy5848 · #1 11-03-2007, 03:10 AM

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

Stevo · #2 11-03-2007, 12:14 PM

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.

Diesel911 · #3 11-03-2007, 01:58 PM

Quote:

Originally Posted by Stevo

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.

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.

Stevo · #4 11-03-2007, 02:12 PM

Quote:

Originally Posted by Diesel911

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"

Diesel911 · #5 11-04-2007, 11:46 AM

Quote:

Originally Posted by Stevo

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?

Hatterasguy · #6 11-04-2007, 12:51 PM

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.

strelnik · #7 04-23-2012, 01:39 AM

Quote:

Originally Posted by Hatterasguy

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.

Even though this may seem like a great design, it is a good design, which means that it's predicated (my opinion) on the assumption that the car will probably be retired after 300,000 miles/500,000 km.

If you look at over-the-road trucks, which are made to be rebuilt after a million miles or so, they have a bolt-on vacuum pump for that reason.

When I get a DeSoto Suburban and redo it with a Perkins diesel engine like its Euro version was, I will use the external vacuum pump on the brake booster, for that reason. Building a truly bulletproof car is not hard, if you want to expend the extra cash.

On the older MBs, it's easier than you think.

Stevo · #8 11-04-2007, 01:13 PM

Quote:

Originally Posted by Diesel911

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

Diesel911 · #9 02-06-2010, 12:44 PM

Quote:

Originally Posted by Stevo

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.

Timer End Play
I went back and took a closer look at both the CD and book Service Manuals and found it listed as: End plan of intermediate sprocket shaft: 0.05-0.12mm.
In section 07.1-240 of the Service Manual.
I assume this measurement is take with the Timer installed on the Shaft and with no Timing Chain on it to interfere with the measurement.
Repeat broke new vacuum pump

Stevo · #10 02-06-2010, 04:00 PM

Quote:

Originally Posted by Diesel911

Timer End Play
I went back and took a closer look at both the CD and book Service Manuals and found it listed as: End plan of intermediate sprocket shaft: 0.05-0.12mm.
In section 07.1-240 of the Service Manual.
I assume this measurement is take with the Timer installed on the Shaft and with no Timing Chain on it to interfere with the measurement.
Repeat broke new vacuum pump

Good show, I dont think the timing chain would interfere the measurement, the intermediate shaft (and TD)will move with the chain on (at least several MMs). wouldn't it be like measuring how far to tighten the nut when doing wheel bearings?

Diesel911 · #11 11-03-2007, 01:43 PM

Quote:

Originally Posted by Jeremy5848

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

nate300d · #12 04-22-2012, 01:59 PM

Quote:

Originally Posted by Jeremy5848

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

This happened to a friend on a 617, but the valve was not damaged. The finger operating the valve is softer metal so it bent. No head removal. He replaced the finger, reapaired the vac. pump and was back in business.

Diesel911 · #13 04-22-2012, 11:03 PM

Quote:

Originally Posted by nate300d

This happened to a friend on a 617, but the valve was not damaged. The finger operating the valve is softer metal so it bent. No head removal. He replaced the finger, reapaired the vac. pump and was back in business.

Unfortunately there is more than one way for the Vacuum Pump to be destroyed.

New Vacuum Pump Ruined due to too much Timer/Intermediate Shaft End Play (the title from my notes).
http://www.peachparts.com/shopforum/showthread.php?t=258062&highlight=vacuum