OK,

So here we go again. This time it is #4 for the 300TD.
I have read that the end-play in the timing apparatus causes the diaphragm to fail? And can someone explain that to me? It seems like the diaphragm material itself is questionable. The first two I replace lasted about 90 days each. After such short lives, I changed brands. That brand lasted about 18 months.
This would tend to eliminate "end play", unless that condition corrected
itself for 18 months of driving?
If end play is indeed a factor, how is it eliminated? Is there a replacement bushing available?
I love these cars, but not fixing the same thing over and over and over again. I would like the REAL fix for this ongoing issue.

Thanks!

glowplugged

I could have missed the threads on that but I thought the End Play issue effected the Piston Type Vacuum Pumps.

On those VPs the end Play causes the Actuator Arm to go in wards far enough that apparently the Piston Bottoms out and the Spring tension is on the Central Bolt/Stud and the Piston Cracks around that Bolt/Stud.

Apparently when the VP is in use the Actuator Arm by way of the Roller/Bearing is always supposed to be in contact with the Timer Cam Face Keeping the Piston from bottoming out or pulled away from the Cam when it is holding Vacuum.

I don't know if the above would do the same to a Diaphragm.

On the Diaphragm one I have read that over tightening the center Bolt/Nut causes it to fail early. Don't know if that was true.

In the Pic see the Worn Bushing comared to the New one in the Pic.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

See if this helps, it worked on mine. Good luck!

Old Style Vacuum Pump to Newer Style

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Diesel911,

I appreciate your response. Even after so many repairs, i don't remember the internals of the pump! My mind must be compensating for a traumatic experience.

Thanks for that bushing picture. I can see that this would cause an over-throw to the pump, since it is in a fixed position. At the moment I can see the possibility that over-throw could be like sticking your hand into a glove, then continuing to pull until it was torn. If this is possible to get that extension of motion in the diaphragm type, it would be possible to cause a tear.
I wonder why there is so much improperly compensated thrust force in that shaft?
It may be that the bushing must be replaced with the diaphragm repair job. What would that job involve? Are the original bushings still available? Should be able to get 200K again out of the diaphragms once that thrust is eliminated. Unless we are getting "NOS" diaphragms. If rubber components are only good for 6 years or so on these cars, it would make sense that diaphragms that were manufactured in the 1980's would randomly fail, with short service lives. The parts may need to be manufactured again, so we have fresh stock. "NNS". New New Stock.
First step: Where to get the bushings; Second step, replacement steps involved; third step, repair diaphragm and cross your fingers? The pump bodies look the same as far as mounting. Can a piston type pump be installed as a relatively easy fix?

So many questions for an old car. But I would like to stop "fixing" it!!!

Thanks!

glowplugged

The bushing is available from the dealer.

However, and please don't be offended when I ask, but are you sure you're installing the diaphragm correctly? The pump must be compressed properly during the installation and the tension cannot be released until after the front cover has been properly re-installed.

Not following that process, and replacing the diaphragm with the pump decompressed for lack of a better term, leads to the diaphragm being stressed during operation leading to premature failure.

Watch this video. It's not an endorsement, obviously, to shop with him or buy his kit. But you'll see that you need to bolt the pump down with a little wood block underneath the pump drive mechanism to compress the spring. You can see what he has fashioned up to do this and perhaps replicate it.

https://www.youtube.com/watch?v=obCFLey6obo

Now, if you've done all this and still have failures then please disregard. But if you haven't, I think it's worth trying one more time before doing any more drastic work.

__________________
1979 300D 040 Black on Black - 1985 300D Maaco job (sadly sprayed over 199 Black Pearl Metallic) on Palamino

http://i.imgur.com/LslW733.jpg

The Baja Arizona Oil Burners Send a message if you'd like to join the fun
Left to Right - UberWasser, Iridium, Stuttgart-->Seattle,, mannys9130

Visit the W123 page on iFixit for over 70 helpful DIY guides!

If you remove the Vacuum Pump and the Timing Chaiin Tensioner you can use a Dial Indicator to check the End Play on the Timer. That will tell you if the Bushing is worn. How much Play is too much is in the DIY Repair Links.

Note that some People claim the Timing Chain Tensioner does not need to be removed.

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84 300D, 82 Volvo 244Gl Diesel

Related to my last post, for validation, attached to this post is the FSM page on replacing the diaphragm. Note the assembly plate that Mercedes says to use. You use part of that assembly plate to preload the diaphragm. The wood plate and block can accomplish the same thing.

Attached Files

43-620.pdf (607.1 KB, 200 views)

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1979 300D 040 Black on Black - 1985 300D Maaco job (sadly sprayed over 199 Black Pearl Metallic) on Palamino

http://i.imgur.com/LslW733.jpg

The Baja Arizona Oil Burners Send a message if you'd like to join the fun
Left to Right - UberWasser, Iridium, Stuttgart-->Seattle,, mannys9130

Visit the W123 page on iFixit for over 70 helpful DIY guides!

Just to clarify, the worn brass bushing does not cause the diaphragm to fail. What happens is the slack caused by the worn bushing allows the pump to slam back and forth, which will eventually destroy the pump. In Diesel911's #2 post thats a pic I took of my pump showing the worn bushing. The timing device had 2.5 mms of lateral play. If you grab your timing device and feel any more that a tiny amount of play thats too much. you dont need to disconnect the chain tensioner. Getting to that bushing is a real pain so I would suggest you make sure thats the problem. When you installed the last diaphragm did you make sure the big washer was facing the right direction and also that you didn't tighten the center screw down too much. Its hard to NOT tighten it down to much. Too tight on that screw will cause the diaphragm to fail.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

OK

I looked at one of the previously failed diaphragms tonight.
The material would probably pass for toilet paper. I tears easily, with little
resemblance to rubber. There is just no strength. The particular piece had no reinforcement fibers whatsoever. A previous one had fibers present, but there were places the "rubber" coating was thin enough to cause the fibers to show through.
I don't understand the need for a "preload". The roller is in full contact with the cam throughout engine rotation. On the other hand, if the preload is to create proper contact of the washer/diaphragm surface before the retining bolt is torqued, I might buy into that.
But if inferior or "past due date" material is used, no procedure or manual can help.


-glowplugged

Where are you getting these parts?

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!