Restoration Difficulty Level

[andyburns]

Anatomy of a T51 ate Brake Booster #2

I have made significant progress and have learnt a lot over the past couple of weeks.  A few other curve balls have presented themselves that I had to deal with that have prevented me from updating in here so I have  quite a bit of catch up.

I ended up buying a huge 45mm spanner to get the nut off.   When I came back to it I started to attempt to take the nut off in situ inside the booster but very quickly discovered that the entire internal mechanism was free spinning in the booster case.  So I obviously had to find another way to retract the mechanism to further work on it.

After about 20s of spinning the internals by hand it became apparent that there were another series of internal barrels that had the same half scalloped ridges that the outer seal employed.  So rotating and gently pulling at the same time allows you to withdraw to the next step.  There are two internal surfaces on the mechanism that you need to do this for in order to clear the outer lip of the casing.  Its kind of like a game of frogga for those who can remember back to the 80's
Once you clear the last ring the entire internal just pop out.

[andyburns]

Anatomy of a T51 ate Brake Booster #3
Once the entire booster internal assembly has been withdrawn from the casing its easy to see how to continue dissasembly. 

I first had to remove the large 45mm nut securing the entire assembly together.  It had been dot punched on the internal thread, slightly distorting the nut and the hollow threaded tube, in order to lock it in place.  Guess this is part of the non serviceable banter you here about these units.

I carefully and very gently peened the threads back into round by tapping an old pair of long nose pliers 50 to 60 times around the indentation and with only hand resistance on the outer ring I managed to get the nut off with not damage.  Its really worth a mention here that the only surface you really have to clamp on to hold the unit while undoing this nut is the steel internal barrel/disc that is bolted to the baker lite hub.

I cant help but wonder if you didn't spend the time carefully sorting out the punched thread that there would be temptation to get a the very big 45mm spanner and just go for gold.  I am almost certain all the load would be transmitted into the bakerlite and could cause more than a few unwanted breakages.
It was interesting to go back to my 230sl booster parts which have been taken apart on at least tow occasions now and examine the thread.  It was a mess with someone obviously in the past hitting it hard just the once to undo the dot punching done at the factory


Once the 45mm nut is off the internal largely fall apart in your hands.  Be carful extracting all the plates as they slide over a central seal that you probably want to preserve in case its still usable.

[andyburns]

Anatomy of a T51 ate Brake Booster #4

One of the only differences I observed while pulling apart the early 230sl booster and this latter T51 was that on the earlier version the two central plates on the early version were spot welded together with small connecting steel plates.  On the later model this was dropped and the two plates obviously were allowed to moved independently.

The diameter is exactly the same as are the two plates.  I cant work out why this change was put in place. 
After the large dish plates are removed the inner baker lite hub assembly end is exposed with the four bolts that secure it to the outer casing.  You have to come in this way to undo gain access to the baker lite.  Its impossible to do any other way. 

Note the very out of round O ring on the end of the tube that has been completely flattened between the nut and the inner tube housing.  I will have to replace this somehow when putting everything back together I guess.

[andyburns]

Anatomy of a T51 ate Brake Booster #5

At this point you will now have the entire baker lite vacume relief valve assembly in your hand which included the rear input rod, bakerlite hub assmbly, and the out put rod that transmits all the assisted braking pressure to the master.

I wish ATE could simply provide this as one spare part.  Other than the external diaphragms tearing all the problems are in this unit.
The first tear down difficulty I had with this was separating the output rod from the baker lite.  Its held in place with a steel cup that is pressed onto the baker lite. 

I am not sure if its supposed to be a tolerance fit or just over the years it has welded itself to the baker lite.
I tried to simply pull it off but was super mindful of damaging the baker lite surface.   There isn't really anything you can clamp to without risking damaging the plastic.  Also bear in mind that the outer bakerlite shaft is a sealing surface against the outer casing seal so if it gets scratched of damaged you may as well throw it away.   

I immediately taped it up with copious amounts of insulation tape to protect it.

I found success separating these parts by clamping the steel output shaft in the vice and very gently using a drift dozens and dozens of times around the circumference of the baker lite making sure I never used excessive force.  I also started off by spraying and soaking the steel cups inner rim with WD40.

Eventually it started to give and then very quickly the entire cup slipped off.  Knowing how delicate the baker lite is I cant stress how carefully I proceeded.  This is the exact location on my other original 230sl booster that the baker lite had fractured right around the circumference. 

[andyburns]

Anatomy of a T51 ate Brake Booster #6

At this point you have the baker lite hub with only the input rod protruding.  It was also a real mystery to me as to how the shaft was held in.  I studied it for twenty minutes or so trying to work it out then went back to the booster parts from my 230.  Bear in mind I didn't pull this booster down so didn't specifically know what parts came from where.


I finally stumbled on a small half circle collar that fitted onto the old input shaft and traced its approximate location back on the new baker lite hub.  There was a tiny slither of what turns out to be rubber sealing a very thin cut out on the baker lite hub that conceal and hold the collar in place.  I also suspect it may also be required to seal the inner working chamber of the hub for vacumn tightness.


I got the smallest jewlers screwdrive I could possibly find and gently worked out the rubber seal.  I have kept this rubber seal in a very secure location while I am restoring the booster.


Once the seal is out the collar simply drops out when you hold the unit upside down and press on the input shaft releasing the pressure on it.  There is a sping on the shaft that holds constant tension against the collar while the shaft is resting.


Once the collar is out the shaft and all its seals can be withdrawn from the middle of the baker lite hub.  I used a squirt of crc around the seals to help it out without damage.  The seals dont normally ride in this direction and risk being pulled inside out and being damaged.

[mbzse]

Anatomy of a T51 ate Brake Booster #6.../...

This is great work you are doing, and perfect that you document it all so well!
Most interesting 

[114015]

...welded itself to the baker lite....

Yes, I do support the (European) baker(y) shops very much - I am a heavy buyer there.

Guess, you are referring to "bakelite" rather than "baker(s) lite" (which is perhaps more healthy than the stuff I am buying),

https://en.wikipedia.org/wiki/Bakelite



Never mind please, Andy...!
Keep on the Excellent Work here!

Best,
Achim

[andyburns]

Thanks achim.  I am blaming that one on my PC auto spell check.  Perhaps I should substitute the word for something else so everyone knows what I am on about.  Any suggestions.  How about brown pig 🐽  That kinda describes that stuff. I shouldnt cast off at it as it's lasted longer than I have been alive I guess.

[andyburns]

Anatomy of a T51 ate Brake Booster #7
Now that I have the input pin out I compared it side by side with the infamous RHD equivalent.

I was fully expecting from all the advice and opinions that I have received that the shaft would be specific in some way to the RHD booster.

I was pleasantly surprised to discover it was absolutely identical in every dimension other than the fork connection to the pedal set rather than the ball in the RHD system.

This has opened up a whole new world as it means that the RHD input shaft can simply be swapped directly into any operable T51 booster and bolted right back in. 

Also this means that there is nothing RHD specific to the Bakelite hub.  This is significant as there is huge number of W108 and W109 sedans out there.  Around 400k were produced to the 50k of the 113.  So any old, even non-functioning, T51 is a candidate for either a rebuild or at least a supply of spare parts.
So now I have the entire booster decomposed I can safely say that there really isn’t that much that can go wrong with them that can’t be fixed… even at home.  The only things that I can see that can cause issues are:
1.   One or both of the dinner plate diaphragms torn
2.   Bakelite hub broken
3.   Input shaft plunger seal to inside Bakelite hub perished
4.   Rear case seal perished
5.   Canter tube seal perished
6.   Case to diaphragm seal not sealing properly

[andyburns]

Anatomy of a T51 ate Brake Booster #8

Comparing other components it’s now apparent that all T51 share the exact same diaphragms.  Both the large dinner plate parts had identical part numbers from the early 230sl T51 to the W108 forked unit.
The central steel tub is also identical.  It seems this component has some sort of coating on it.  My early 230 part is showing a lot of wear and is completely worn off in places.  This surface is what the central vacuum seal runs on so I am going to use the better part when I reassemble.

I am still not certain which booster shell I will run with.  The old unit is much more pitted from old external and internal rust as the new unit. 
Also the issue of the clearance to the inlet manifold would be solved with the newer unit so  am tending to just swap my input rod into this and fully restore that unit.

At least I have options now!

[66andBlue]

Andy,
thank you for taking us along on this very interesting story! 👍

[andyburns]

Anatomy of a T51 ate Brake Booster #9

Some more photos of the differences for you.  I talked about the central plates in the early booster being joined with steel tabs.  I have taken a photo of this to try and show this.

Also the front booster base cover I have talked about being convex rather than the early concave one.  See below the photo that shows them side by side and how much more room you have to clear the inlet manifold on RHD vehicles.   The older concave cover is almost twice the weight of the convex equivilent.  It has an extra internal back wall welded in.  Presumably the designers were trying to create a larger vacumn cavity but probably discovered the advantage was neglagable and decided to revert to a simpler lighter design.  Would have loved to have been a fly on the wall.




The output shaft is identical.  I measure the length and diameter to confirm.

[66andBlue]

Happy Anniversary, Andy!

[andyburns]

Awwwww, thanks Alfred.  Pretty happy with the new model.  Quite a few new features that the old one didn't have and much better road holding.

[AndrewB]

Hi Andy, it seems like this thread stops after your MASTERCLASS #9 on ATE boosters. Did you reassemble the RHD brake booster using your new findings regarding LHD/RHD booster differences being only the fork vs ball, and how has it worked for you ? I also have a RHD Pagoda, so am interested in your experience here

Also, did you redo your hardtop yet ? Again, would be interested to know how it went.

Thank you for a fabulously detailed and documented restoration master class

Regards
Andrew

[andyburns]

Hi Andrew.   I got the booster back together and it worked just fine.  No where near as scary as people would lead you to believe.  The only difference us the ball.  You can buy any good second hand W108 booster and it will swap across just fine.

I havnt posted any more as I sold the pagoda.  Was a very very difficult decision but the money offered was too good to refuse.   

I have moved onto my next project now a R107 which I just love. 

[AndrewB]

Hi Andy

Thank you for getting back so quickly. Really good to know about the booster, you did us all a huge favour with your inquisitive approach and commitment to documenting everything.

When I was looking to buy my Pagoda, I saw a lot that had been "restored" but which were actually incredibly shoddy (cheap paint and carpet - not sure what I was looking at, but it was overpriced and a shame that they had not done the job properly - in most cases charging as if they had). The UK has many people wanting to make a quick buck out of old cars.

There are a few craftsmen who restore these cars properly (some of whom are members here), but many more who do a lousy job and hope to charge top dollar.

Your car would have been in a very different league. I am sure that the new owner is delighted with it, they have certainly bought a car that was a labour of love and where every detail was carefully ensured to be 100% correct. It would have been worth every dollar they paid you for it.

I looked for many years for a car, despairing that prices were rising, but quality was not at the same level.

In the end I managed to find an "unrestored" 1969 model, which, as far as I can tell, has never been painted. It is unmolested (matching numbers) and authentic, however it is not perfect and has number of minor scratches and scars of the last 50 years. I intend to enjoy it, and one day, if needs be, will have it carefully restored. It will cost a fortune to do as beautifully as you did yours.

Enjoy the 107's !

Andrew

[andyburns]

Hi Andrew.  Thanks for the kind words.  The 113 was a huge part of my life for a few years.  It was a love hate relationship though.  Such a fiddly pedantic thing to work on.  Learnt heaps and feel privileged to have had the opportunity.  I am still physically feeling the consequences of it on a daily basis.  The spinal injury I sustained while lifting the gearbox has been life changing.  Make sure you never make the same mistake.  Constant back pain and further operations hang over me like a dark cloud.  Still no regrets.. could have just as easily been my kids I was picking up off the ground.  Have you got any photos of your sl.  I would love to see them.  Which part of the uk do you live in.

[AndrewB]

Hi Andy

I live in Surrey, south of London, and outside of the "urban/suburban edge", so we have the benefit of being surrounded by woods and fields, but still an easy train ride into London as required.

Your back injury really seems to have been nasty - as you say, you could have picked up a child from the floor and had the same outcome. Nevertheless, it is something that will live with you forever

I have attached some pics of my car

All the best,
Andrew

[114015]

I havnt posted any more as I sold the pagoda.  Was a very very difficult decision but the money offered was too good to refuse. 

Hi Andy,
So good to see you back here! 
Learned soo much from you and your comprehensive restoration story,
really made my own endeavours during restoration easier here and there...
Thank you so much for your impressive stories !

Very sad that you sold your Pagoda - but most important, you are still around here.
Highly appreciate this.

Looking forward to hearing from you in the future again.

All best to NZ,

Achim

[Neil Thompson]

Nice looking car AndrewB, looks like a Silver Arrows advert almost

Neil

[AndrewB]

The pics are from Michael Lavers - I bought the Pagoda from him

[andyburns]

Hi all.  Just thought I would pop in and say hi.  Hope everyone is keeping well and are getting out and about in these lovely cars.  I must say I am missing mine.  The 107 has taken some of the pain away.  I am really enjoying it getting out most weekends.  I have just finished my fourth house renovation in three years so am probably going to move on to the 107 to keep me busy.  Gotta have a project right?

[rwmastel]

Dave,  ... I think I am just at that point of 'when the hell is this going to be over'. 

This was from Andy's second post, back on page 1, in 2013.

Hi Andrew.   ... I havn't posted any more as I sold the pagoda.  Was a very very difficult decision but the money offered was too good to refuse.   

So, I guess he finally got his answer.  What a project!

I wasn't very active on the forums during Andy's journey, so I think I'll make it a point to go back and read as much of this as I can.  As I embark on my own 230SL work, to a MUCH lesser level of intensity than Andy's work, I hope to find information and inspiration in these 74 pages of posts.