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Brake Master Cylinder dismantling

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jjbunn

jjbunn

Jedi Knight
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The brake cylinder was leaking around the nylon sleeve, and so I set about dismantling it so that I could replace the sleeve and the various rubber seals with the rebuild kit I'd bought from Moss.

This proved to be a tricky job! First I used an old tube shield part to tension the plunger spring so that I could remove the lock spring at the top.

brake_master_cylinder1.gif


Especially hard was removing the nylon sleeve, which the Haynes manual implied should come out easily. It didn't! I remember Tony saying something about needing two long screws, and I guessed for what. So I carefully drilled two pilot holes in the sleeve, and then used the screws and a small piece of plywood with a couple of holes drilled in it as a brace. By carefully tightening the screws, the nylon sleeve slowly came out. Of course I completely destroyed it in the process! The rebuild kit contains a replacement.

Here is a photo of the disassembled innards.
brake_master_cylinder2.gif


Now my next problem is how to remove the small pins that hold the collars on the inner spring. Do I knock them out somehow? Again, the Haynes manual is unhelpful.
 
Job 1 is to inspect the bore for *any* signs of pitting. The piston looks pretty scored to me. I've rebuilt a few and just buy a new (Lucas/Lockheed) unit. Not worth the time/hassle to R+R it and find out it leaks. YMMV.

Oh, and removing the pins is easy compared to reinstalling them. As I recall, you you need to compress the spring to get at it. If you can't tell, I'm not a big fan of rebuilding these.
 
/ubbthreads/images/graemlins/iagree.gif Yep, pushing them out is easy compared to putting them back in!

(& everybody needs to do this job once! hehehehe...then, they'll never do it again! & will understand why the MC's are priced like they are.)
 
Thanks guys.

The cylinder is as clean and shiny and blemish free as can be imagined - you could eat your dinner off it!

The piston is unblemished except right at the exposed/pedal end, where there is some scoring from the screws I used to extract the guide washer (whoops!). But this part of the piston never moves inside the guide washer, so I believe it's OK.

I came across this article from the old Saab fans: https://www.vsaab.com/html/Articles/brakemaster.htm

which is very helpful. It's not the same cylinder, but it's close. They say not to completely remove the pin.

The reason I'm doing this rather than just buying a new one is mainly for fun ... and I bet you guys with more experience are probably right: I'll end up having to fork out for a new one anyway. We'll see.

Thanks again.
 
I tapped one of the pins half way out, which allowed me to unhook the spring guide loop. Then I removed and replaced all the washers and rubber parts etc.. Refitting was pretty easy: I caught the loop back over the pin inside the collar, and then fed a nail through the opposite side of the pin, which mated with the open end of the pin inside the collar, so preventing the guide loop from coming off while I tapped the pin back into position.

After cleaning up and replacing all the innards and spring clips, everything looks good: no more leaks from around the nylon washer! So I'm cautiously optimistic I've fixed the problem.
 
A couple of pics:

During replacement of the seals, spring detached, pin half out:
piston-apart.gif


Reassembled:
piston-reassembled.gif
 
Julian: I gotta say: your engineering "sense" is impeccable. You only lack the LBC-specific experience!!! Take yer time and come ask when ya find a "wierd" situation.

Great job, BTW!!!

...and do you wrench on that 911? /ubbthreads/images/graemlins/grin.gif
 
I feel better about rebuilding the master cylinders on the '64. They appear to be fairly simple in comparison. I'm rebuilding them this weekend after receiving my giant box of new parts this week.

Cheers,
 
Thanks /ubbthreads/images/graemlins/smile.gif

Wrenching the 911 is a good question. I've had it since July, and the only thing I've needed to do is replace the air filter, and reattach a grounding strap. When I started looking I was expecting to have to do quite a bit of work on whatever 964 I ended up buying, but the one I got has no urgent issues (I mean, it leaks a little oil, a couple of drops a week - but they all do - and it could probably use a new A/C belt) Which is why I bought the MGB, to satisy my need to tinker on a car. The MGB has the advantage that it's a heck of a lot simpler than the 964, so it's something I can tackle.

The 911 goes like a bomb ... take the revs above about 4000 and the sound is a glorious, intoxicating cacophonous scream of metal bits revolving in oil /ubbthreads/images/graemlins/driving.gif Some info here if interested: Porsche 911
 
umm... just mildly curious. I'm a Porsche "Certified" wrench.

"All my friends, they drive Porch-ees..."
 
[ QUOTE ]
umm... I'm a Porsche "Certified" wrench.



[/ QUOTE ]

Yup, you're "certified" alright ... /ubbthreads/images/graemlins/devilgrin.gif /ubbthreads/images/graemlins/jester.gif /ubbthreads/images/graemlins/angel.gif
 
Certifiable is prob more correct. :p
 
Well!!! I've NEVER been so insulted in all my life!!!


...oh, wait.... mebbe ONCE... err... then there was that time...


ohnevermind. Okay. Youse-guys may have a point. *sigh*
 
"Ding - ding"....fighters move to a neutral corner....
 
Hehe, Beep beep, Bugeye comming through.
 
Whattheheckwazzat?!?! Where'd it come from?!?! Where'd it GO?!?! /ubbthreads/images/graemlins/wink.gif
 
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