Master Cylinder Rebuild

[Tlauden]

After reading every thread after searching about these I'm still a bit in the dark. With the brakes locking up on the deuce and with the airpack eliminated as the problem I'm going to go ahead and do a master cylinder rebuild. I got a rebuild kit or $26 from Saturn surplus today and there looks to be a bunch of small parts, I'll take lots of pics and I'm going to print the section in the TM's about the MC.

My question to you folks is:

Any tips/tricks anyone have to offer on tearing these apart?


This will be my first time ever working on a MC so I guess I'll see how it goes...

 

[poppop]

Its pretty straight forward. Hone it and make sure it looks slick on the inside. If its had silicon fluid all its life it will probably clean up nice. Check the small holes in the bottom to be sure they are open. Lots of times these return ports are blocked and that is waht makes the brakes lock. Also check the petal pushrod adjustment. It has to have some freeplay in it to allow the piston to return all the way home and unblock the return port. Remember as things heat up they expand so a little to much free travel is better that not enough.

 

[rlwm211]

What poppop said is spot on. I would add make sure everything is CLEAN when you put it together. Also coat the bore and the piston seals with Silicone brake fluid before you assemble everything.

One other thought...When you pull the spring cliip that holds the piston in the bore make sure you have it held in place so as you carefully allow the piston to come out you can see the spring and check valve orientation.

RL

 

[Tlauden]

thanks guys ill let ya know how it goes, heading out to pull it off the truck right now

 

[Tlauden]

ok, So its off to the parts store for more brake cleaner, I do believe this was my problem, the piston was fully compressed and stuck there. once i got it released a TON of nasty sludgy stuff came out. well after cleaning the main piston area and quickly putting in the new spring, piston, and cup. they move up and down great!! but there is still tons of sludgy stuff in the fluid reservoir part.


heres a pic of the stuff that came out of the piston area

The big puddle is the brake fluid, black globs are the gunk

 

[rlwm211]

Glad you found the problem.

RL

 

[Tlauden]

Ok, just to finish off the thread. Got the master cylinder working and the brakes bleed. Works good. The only thi g is I do believe the push rod going Into the master needs adjusting. After releasing the brakes I believe the fluid drains back too slow. The thump of the big piston In the airpack can be heard about four seconds after I release the pressure returning to position.

 

[gimpyrobb]

Pull it and hone it. You have been warned, you might need to rebuild it. That sludge is prolly in the air pack too.

 

[Tlauden]

Ok thanks although It didn't look like it needed honed. the inside of the master looked great once I cleaned it. And I had the airpack pulled apart and we cleaned it also.

 

[kennys@wi.rr.com]

Looks can be deceiving. If the job is worth doing, it's worth doing it right the first time. By taking 5 minutes to hone it now it will save you plenty down the road. Just my 2 pennies rubbing together here.

 

[nk14zp]

When you did the airpack did you oil it?

 

[Tlauden]

Yes, we put a little in. I just went out and added some more, probably about 4 ounces into the little port on the back of the air pack. Figured maybe We didnt put enough in the first time

 

[M35A2-AZ]

When you use the hone do you need to use the hone with the three flats on it or the one with all the little beads?
Thanks!!

 

[rlwm211]

I use a 3 stone hone. You do not want crosshatching like a cylinder wall in an engine.

Stay in one place, move a half a stone length, stay there, and then continue moving along the bore to the end and then back the same way. This gives a nice 'polish' to the bore.

I use a light lubricant like WD40.

If this is your master be sure the tiny return hole does not get plugged up.

RL

 

[M35A2-AZ]

I use a 3 stone hone. You do not want crosshatching like a cylinder wall in an engine.

Stay in one place, move a half a stone length, stay there, and then continue moving along the bore to the end and then back the same way. This gives a nice 'polish' to the bore.

I use a light lubricant like WD40.

If this is your master be sure the tiny return hole does not get plugged up.

RL

Thanks, That is what I was thinking on the type, but I wanted to ask.