Brake Booster Plastic Sleeve Broken - Is There A Remedy?

[Pawel66]

I had a nice, rebuilt brake booster as a spare. Now my mechanic dropped it and the plastic sleeve cracked.

Is there a way to fix it?

There is a thread about broken sleeve, but I could not find any info on how to repair it.

[dirkbalter]

Hi Pawel,

https://www.sl113.org/forums/index.php?topic=32294.0

Had the same issue with a broken plastic sleeve when the BB was shipped. However, I have an early T51 (230) BB. I am not an expert (lol) but believe the later BB'S are different. A little while ago a bought a spare brake booster for my 108, which I believe is similar to yours from a local supplier for less than $200.
(I made a plastic sleeve and may be able yo help you but I don't know if its the same.)
Dirk

[Pawel66]

Dirk, thank you! I apparently did not catch this thread on broken plastic sleeve.

Thank you for your kind attention. I will make pictures as soon as I get to the shop - the booster broke down 6 years ago, I found a replacement and sent it for re-building. It came back and went on the shelf, until last week when it fell on the floor... I do not remember which one was it.

[pj]

My brake booster has failed. Dan (Benz Dr.) has described the process of removing it, so I'm willing to give it a try. (Normally, I'm a complete klutz when it comes to mechanical things, if you hear a scream of anguish, it's probably me.) I'm particularly worried about what's supporting the brake booster from underneath, where I can't see it. Or are the four bolts attached to the funny-shaped bracket all that's holding the thing in place?

I wonder if anyone has a video or even some photos that might help me visualize the removal process before I end up with an exploded cuckoo clock. Is it safe to presume that the location and structure of a brake booster is one of the few things that's very common among all vehicles, so a Chevy truck video like this
www.youtube.com/watch?v=2MWb7kYIx68
might actually be helpful?

One of our members often posts photos from his shop on Facebook, and he recently posted this photo of the funny-shaped bracket that holds the brake booster. Has he got this correct? Is this where the bolts come out to remove the brake booster?

I notice that the relevant section of our Technical Manual has lots of words, but gosh they are disorganized. A useful project for someone to improve that content?

[Pawel66]

I am not a mechanic, but I replaced this booster some years ago and installed one I have now. There are threads on this, the Forum helped me - you may want to search.

The booster is held on the 4 screws attached to the bracket as you see on the picture. But on the other side there is the master cylinder. I managed to move it away, but I have copper brake lines. You may not be able to do it with steel ones. So, I guess, you would need to drain the fluid and undo the brake lines from master cylinder.

I also made some marks on the bolt holding the levers form brake pedal. It is an adjustable connection (eccentric bolt).

[Shvegel]

As Pawel states there is a cam or eccentric bolt on the linkage.  The bolt my pen is pointing to.  Mark the position of the bolt (not the nut) before you remove it.

Remove the large vacuum line next while the booster is still bolted in and stable.

Then remove the 2 nuts holding the brake master cylinder to the booster and pull the master cylinder out.

Finally remove the 4 nuts that retain the booster to the aluminum bracket.

There is an O-ring seal between the master cylinder and the booster. It is best to replace it (I am sure Mercedes sells it) or at least inspect it for damage before you reassemble it. It fits in the groove on the rear of the master cylinder.

[Shvegel]

Dirk,
Curious which plastic you used for the sleeve?  Delrin?

[Pawel66]

There is an O-ring seal between the master cylinder and the booster. It is best to replace it (I am sure Mercedes sells it) or at least inspect it for damage before you reassemble it. It fits in the groove on the rear of the master cylinder.

I forgot to mention this oring and it is important. since it does not cost a lot and is available at the dealers, I would just replace it, PN A 004 997 32 45.

[dirkbalter]

Dirk,
Curious which plastic you used for the sleeve?  Delrin?

Pat,
Its printed in ABS. I like Delrin, especially for bearing applications but I can't print it. The sleeve doesn't see any real stress or forces during operation and I believe  ABS is sufficient. Even though printing is good as far as dimension and tolerances is concerned, the problem is that the surface finish is not as good as machined. I did polish the OD and ID afterwards to get a good seal surface.

[Pawel66]

What do you think is the material that sleeve is made of? Is it bakelite?

[dirkbalter]

Yes it is. And it gets brittle over time.

[Pawel66]

Thank you. I studied a bit about what kind of glue to use- perhaps it will work this way...

[dirkbalter]

Pawel,
I would be careful with gluing. Take a look, I made an extra one at the time. If it’s the same, you can have it for your guy to test.

[mrfatboy]

Should this be added to the 3D printed parts section of the Tech Manual?

[Pawel66]

Pawel,
I would be careful with gluing. Take a look, I made an extra one at the time. If it’s the same, you can have it for your guy to test.

Dirk, this looks like the best solution indeed! I will get there Friday to pick up the booster.

[Shvegel]

Dirk,
That's really cool.  I really need to learn more about 3D printing.  That would be near impossible for me to make with my Lathe and Milling Machine but a printed one would only take a couple minutes to clean up on a Lathe. 

[stickandrudderman]

I am down this road already.
I have drawings and now have a stock of 3d printed parts but they do indeed need hand finishing in order to get a smooth enough finish for lip seals to operate on.
For that reason I am not selling them as a spare part, only as part of an overhauled exchange programme for complete boosters.

[dirkbalter]

I am down this road already.
I have drawings and now have a stock of 3d printed parts but they do indeed need hand finishing in order to get a smooth enough finish for lip seals to operate on.
For that reason I am not selling them as a spare part, only as part of an overhauled exchange programme for complete boosters.

I fully agree. Due to the safety sensitive nature of the part, I am not comfortable to sell or share the part either. However, I am working with a local bb rebuilder who can supply a fully rebuild unit (exchange) on this side of the pond. Feel free to contact me if needed.

[Pawel66]

Enclosed are the pictures of my spare booster deprived of the sleeve...

[dirkbalter]

Pawel, yours looks like my 230 one (T51). The gray one next to it is for a 280 with no marking, just ate.
The distance from the center of the hole to the mounting face is approx. 115mm

[Pawel66]

Thank you! Will check, but it does look the same. i will PM you.