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Brake Master cylinder — rebuild or replace with new

I said the brake master was "dry" ... You should use some brake fluid in the bore when assembling. The rubber needs some lubrication to move freely.
 
Hey Mike
Is dribbling some brake fluid into the line ports good enough for lubricating the rubber or should I pull the push rod and “guts” out—lubricate and slide it all back into place before mounting the new MC on the car?
Andrew
 
Thanks Puff for the reply.
So are you saying to disassemble the MC and lubricate it before it goes on the car?

If so, while I am sure “red rubber “ grease is a good product, what would I use if I just went to my local Napa, O’Reily’s or Advanced?
Andrew
 
Thanks Puff for the reply.
So are you saying to disassemble the MC and lubricate it before it goes on the car?

If so, while I am sure “red rubber “ grease is a good product, what would I use if I just went to my local Napa, O’Reily’s or Advanced?
Andrew
Yep, if it has not been lubricated upon assembly, then disassembling and lubing it is a reasonable path forward. Most are factory lubricated, however.

Do NOT use any other grease other than red rubber grease. It is the only grease that I know of that is correct and compatible with the rubber seals and hydraulic fluids in British cars.
 
It is late in the evening and I am not in my garage, but I was reading the brake MC on and off procedure ( all bits are up threaded and on the car but all needs to be bolted down tight ) and looking at a few pictures and found myself a bit panicky and on the horns of a dilemma.

I just noticed that when installing a master cylinder there is something called a “distance piece”. One did not come with my new brake master cylinder ,but I seem to recall one on my old mc.

If my memory is accurate - I will know tomorrow- but was I supposed to reuse my old distance piece on my new master cylinder — between the firewall and the brake master cylinder mounting?

Thanks and assure me if you can that all is Ok and I didn’t mess anything up and I just need to undo 2 nuts and insert the distance piece.

Andrew
 
I think you mean the spacer that goes between the MC and the firewall .. you need to reuse it or the pushrod will be too long for the MC
 
Yes ,It is a spacer although the wsm refers to it as a “distance piece”. *#$#*#—I am going to have to take apart some hard earned gains only to redo the work with the spacer back in place.
Being an older guy with a lot of aches, pains and injuries does not make this task any easier! Oh well, its what we do.
Thanks — I will let the forum know how it goes if I can get myself out of the footwell. If you don’t here back call 911.
 
Well I am out of the footwell —- for now, but will be heading back today and I have an issue on which I could use some advice.

As you all know, I pretty much had to undo everything to install the spacer/ distance piece- challenging but doable. I now have the spacer on the engine bay side of the firewall - please say that is correct- but there is no way that rubber cap on my new brake master cylinder was going to fit into that mounting hole and make it through to the footwell side. Today I will try again to convince it in place, but yesterday was a nogo— the mc does not go deep enough into the footwell to provide clear access to the groove on which the rubber needs to be. That said, when I looked at my old mc , it was clear that the pieces where not the same. On the old mc the rubber seemed to come from within the round end as opposed to gripping the outside of the round end at the piston rod. I will try to tuck it in , but I am afraid the hole in the fire wall is simply to narrow for the new design.

I assume that this is a “dust cover” and does not affect the function of the pedal or braking. My options as I see it:
1) take everything down again and ream the hole just a tad larger
2) fashion a dust cover with something I have lying around my shop - bicycle inner tube— bottle cap— ????
3) do not bother with the dust cap and simply leave it off

Another concern: I the heat of the moment, I lost track of which hole the the clevis pin came from. I will look for markings, but if I cannot find any, do you folks have any advice for me. Note** the new mc has adjustment capability on the push rod that the old mc did not. I suppose push rod travel could be adjusted to either hole, but I do not yet know. When adjusting the push rod on the new mc, is there a process I should know about? Ex pedal out push rod pulled toward the drivers seat or pedal depressed and push rod pushed forward toward the mc body. What am I looking for in the new world of the ability to adjust the push rod?

A lot for you all to consider— if you have questions please ask— comments / corrections always appreciated- I will also be glad to provide pictures of anything to help clarify my questions.

Be well all
Andrew
PS:
My car has been down so long at this point, sending the old mc out to be resleeved would not have been a problem.
 
If the new MC has an adjustable push rod length, maybe you don't need the distance piece. You can probably work that out by laying out the original MC (with the spacer) and replacement MC (without spacer) side by side and checking the lengths of the push rods.

What MC did you buy? Sounds like something aftermarket.

I think the pin is in the upper hole on my SV.
1731019283421.png
Mike
 
I am working on a clutch master cylinder on my car, and I set the clutch pedal pin to be the same height as the brake pedal (also the upper hole)
 
I am jammed up for much of today, but I will take pictures and post them when I can. What surprisingly seemed to work out was when I forced the rubber dust cover up onto the footwell side of the brake mc, the return spring slipped over it and seems to hold it place. The spring seems pretty secure on the rubber dust cover and does not ride up when the pedal is moved - amazed here and glad I tried it.
Questions for now:
Erny: is your clutch mc new or rehabbed? Is your pedal adjustable beyond the two hole clevis pin fitting?

Mike: I bought what SS had to sell - no options/ choice. No box , wrapped in paper ($138). I did not notice any manufacturer markings. Hopefully my pictures will show this ,but the new brake mc has a threaded push rod and U shaped slide - holes in the slide for the pedal clevis fitting and nuts on both sides of the U slide threaded onto the push rod, one nut moves with the slide and the other is most likely to lock the adjustment in place. I will have to get a wrench in the spring winding to reach the lock nut. Not yet sure about locking it down (only bit not yet locked down) . I will probably have to wait until I put fluid in the system and better understand pedal travel. Buying new fluid tomorrow.

I have , I hope/ believe, everything up and in place so measuring with the spacer and not is not a reasonable option at this point. Spacer in place. My clevis pin is in the lower hole for now but I will see if by using the other hole I will get closer to the height of the clutch pedal- pretty close now.
This has been a long posting so I cannot recall who suggested zip ties to compress the return spring to make room to insert the disc with the slip cut — but It is a brilliant tip— absolutely brilliant. As you all know there is not much room to work - I was upside down on my back. With zip ties I compressed the spring to near flat and even in that environment it slipped together very easily- I reach in with a razor blade to cut the zips and hopefully my pictures will show a workable job done. Thanks again to whoever suggested the zip ties!!!

I will update when I can
Thanks for all for the input, advice and that huge tip about the zip ties!!
Andrew
 
Questions for now:
Erny: is your clutch mc new or rehabbed? Is your pedal adjustable beyond the two hole clevis pin fitting?


Just posted in a different thread. I could not get a new clutch master so we adapted a TR6 clutch master.

It is not adjustable.. I had to swap the Sunbeam pushrod instead of the triumph piece as it is wider but the same length.
the new part fit in the firewall the same, but we needed new/different pipe and fittings than what was there before.

Hope this helps.
I also used the zip tie method for holding the spring compressed (but just used wire ties) and it made the job so much easier than my prior attempts.

54106586137_0aec70e7d1_b.jpg
 
I believe I had mentioned that I had used zip ties to compress the spring in some previous thread. I probably got the idea from someone else.
 
Well, this is what I am looking at( pics below). Please let me know if you see something goofy, not right , dangerous or if things look OK, adequate or outstanding say so too— that will help too. If you have questions sing out!

As I see it, all I need to do, at this point, is secure the adjuster on the push rod, add brake fluid and bleed-( literally).

On Mike’s recommendation a while back I bought speed bleeders ( one person bleeders). It appears I used them successfully before but I now have a question. If you are sitting in the driver’s seat operating the pedal, how do you know that all the air is purged unless you are looking at the absence of air bubbles in the bleed line? Do I need to be in two places at once?

Any thoughts on pedal travel and the adjuster?

Hey Mike— sorry for not immediately recalling you were responsible for sharing that brilliant idea of using zip ties to compress the spring.

Heading out to my shop in a few hours. It would be great if I could get some feedback before todays wrenching. If not, I know you guys will be there to help correct yet another flub.

Be well
Andrew
 

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The speed bleeders have a one-way valve. When bleeding the brakes, you can do some pedal pumping then hop out of the car and see if the clear tube attached to the bleeder has air bubbles in it. If yes, continue bleeding until you do not see air bubbles. You could also do a facetime with two phones or a phone and an ipad ... The brake reservoir holds a decent amount of fluid, so you can do a decent number of pedal pumps before checking the clear tube for air bubbles.
 
Not been a good day.
I attached a bleeder hose to my speed bleeder- filled the resevoir— loosened the bleeder -pumped my pedal many , many, many times and no fluid was moving at all.

I thought maybe move the clevis pin to where others have it and dropped the clevis pin into a place where things get lost. I hope I will find the clevis pins before I find Jimmy Hoffa.

Question: why is my brake fluid not moving with the resevoir full and the bleeder open?

Heading back to my shop to continue my search— no pin - no pedal.
Please help if you can
Andrew
 
Not been a good day.
I attached a bleeder hose to my speed bleeder- filled the resevoir— loosened the bleeder -pumped my pedal many , many, many times and no fluid was moving at all.

I thought maybe move the clevis pin to where others have it and dropped the clevis pin into a place where things get lost. I hope I will find the clevis pins before I find Jimmy Hoffa.

Question: why is my brake fluid not moving with the resevoir full and the bleeder open?

Heading back to my shop to continue my search— no pin - no pedal.
Please help if you can
Andrew


Could be a blocked reservoir-to-MC tube, but I suspect that the MC piston is not being fully retracted and opening the port that connects to the reservoir because the MC pushrod is too long. Could also be that the MC return spring is not fully retracting the brake pedal arm / pushrod / MC piston. Just my best SWAG's based on how you got to where you are.

I have learned the hard way that a MC should be tested on the workbench before putting it in the car.
 
Last edited:
I did not find Jimmy Hoffa.
I did, however, find my clevis pin. It got hung up in the gas pedal mechanics and never made it to the carpet.

On brake master cylinder:
The mechanism seemed to be working pretty well so I assumed it was a hydraulic malfunction. Since I drained down the fluid from the bleeder on the left front wheel to clear my old mc for removal, my assumption was that air was not being released and the air blockage had nowhere to go as it was blocked by fluid on the back side and fluid on the top side. I opened the bleeder on the left rear wheel - pumped - and everything started to move again. Once I passed some fluid and air through the left rear bleeder, my assumption was that all should work as designed. It did! I then bled as I was instructed to and now have plenty of pedal and 1966 stopping power. All my piston travel and pedal adjustments were eyeball estimates as I really had nothing else to go on.
“ A long strange trip”and back on the road!
Thanks all for advice and counsel. I have said it before, but without this forum, I would have given up on any number of Sunbeam projects. As I stumble through my car hobby, you folks never fail to come through with help.
Thanks again and again!
Andrew
 
Hard to believe that I have not covered all there is to be aware of when changing out an old brake master cylinder for a new aftermarket one. There is however one other aspect of our cars to reveal that shade tree mechanics like myself will probably not know.

I was advised to remove the remote fluid resevoir so as not to stress or break the lines when reconnecting the mc. I did this and the line hook up was pretty simple. What I did not know and learned the hard way was the single bold that holds the remote reservoir to the firewall is threaded into fixed threads in the bracket which holds the brake pedal to the firewall. When I removed the top bolt which holds the master cylinder in place, that fix threaded bracket hole pulled away from the cabin side of the firewall. At this time, I did not know the connecting sequence. I assume I had dropped a nut or had bodged threads when trying to reconnect the remote reservoir. It was not until the brake pedal fell onto my face that I saw the fixed threaded hole at the top of the brake pedal bracket. Impossible to see even when on ones back in the footwell.
Once I saw how the connection was to be made, even with my smallish arm reach ( 5’ 9”), I was able to start the nut on the engine bay firewall while applying adequate pressure pulling up on the brake pedal. Tough reach — just enough.

That should do it for my experience.
Be well
Over and out — for now
Andrew
 
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