Brake Overhaul - Rear Master Cylinder Leak question

[scott]

Chuck have you got a screwdriver that goes round corners? Just kidding but obviously you can do that on the MCs that have an 'in-line' banjo but when they are at 90 degrees it won't work.

Okay - I was trying to understand how that would work and couldn't figure it out (I tried sticking something in there for the heck of it though).

I've gotten the piston rod out to ALMOST flush with the master cylinder end but still haven't gotten it out yet. I've tried spraying some silicon lubricant around the ripped dust boot but it hasn't helped much. I guess I could try spraying some in the banjo hole. Unfortunately I don't have a blow torch - uh, I guess I could try my wife's hair dryer. I just keep pulling with the vise grips hoping it will break loose. So far, no luck.

[chuck hahn]

I didnt see the hookup spot..just the top view he posted..Yeah im am "spoiled" i guess on how easy the 78 and 79s are straight inline setups. Wonder if some sort of small diameter long spring would work..kinda like those springy drain snakes go around corners in the drains ??? Maybe put the resivoir and cover back on with a home made cardboard gasket and some compressed air in the banjo hole???

[G. Bruns]

Did you try PB Buster? I had the same problem and it freed it.

[scott]

Did you try PB Buster? I had the same problem and it freed it.

I hadn't but I put some in there this afternoon - after a few hours it didn't come out but I'll let it sit over night.

I didnt see the hookup spot..just the top view he posted..Yeah im am "spoiled" i guess on how easy the 78 and 79s are straight inline setups. Wonder if some sort of small diameter long spring would work..kinda like those springy drain snakes go around corners in the drains ??? Maybe put the resivoir and cover back on with a home made cardboard gasket and some compressed air in the banjo hole???

I only have a weak tire air compressor but I may have to try it.

It seems odd that it is making this "good" of a seal!

[G. Bruns]

Spray some more in tomorrow and try to spin it. Don't even try to pull until you can get it to spin. Once it twists a little, spray some more PB Buster in there until it comes free. Be careful with compressed air. You've got a potential bullet there.

[scott]

Spray some more in tomorrow and try to spin it. Don't even try to pull until you can get it to spin. Once it twists a little, spray some more PB Buster in there until it comes free. Be careful with compressed air. You've got a potential bullet there.

No luck with the PB Blaster or my small air compressor.

The push rod spins fine - it just doesn't pull out. If the front is similar to the back and there is a push rod with a "cap", maybe the cap part is rusted to the master cylinder body?

[hampshirehog]

You're going to have to resort to heat. PITA as you have to take the plastic bits off and repaint the thing but sometimes it's the only way.

[chuck hahn]

Shouldnt be a cap per say..maybe a washer is rusted in place. Take a small flat tip and see if you can hook it just under the edge of any lip and try to gently pry it up.Maybe take a wire bent at a 90 and feel around to see if it " slips under " any rim just below the leading edge.

[scott]

Success! I was able to hook the end of the ripped boot with a pick and put it out some before it snapped. Then I used needle nose pliers to keep pulling at the pieces of rubber until I got most of it out. Then it all pretty much fell out! Thanks for helping with all the ideas.

Of course, now that I can inspect the bore and it doesn't look as good as the rear master cylinder. It seems to be rusted near where the oring was. Is this shot? I may need to get a better pic.

[chuck hahn]

bore brush and some hoppes number 9 is my go to soultion for removing that crap..get it scrubbed out real ggod and then youll be able to see what going on better..so there was a bit of boot rubber holding it back then?? I hadnt thought of that possibility, but i will remember it.

[scott]

bore brush and some hoppes number 9 is my go to soultion for removing that crap..get it scrubbed out real ggod and then youll be able to see what going on better..

I'll see if I can get my hands on that. I thought MAYBE it could be that it's only the groove holding the snap ring / circlip that rusted rather than the o-ring groove.

so there was a bit of boot rubber holding it back then?? I hadnt thought of that possibility, but i will remember it.

Apparently. When I tried to remove the boot, it ripped off and left the bottom part. I didn't think it would be an issue. Should the boot wrap around the washer? It seemed like it was in my case.

[scott]

I picked up some Hoppes Number 9 and a gun cleaning kit that includes various bore brushes. I applied the solvent with q-tips and scrubbed with the brass bore brushes. It definitely seemed to help.

I'm having a hell of a time photographing the bore - this isn't really what it looks like to my eyes but:


It seems like the rust/pitting stops at the grooves. Deeper in, everything seems smooth.

[chuck hahn]

Youll probably be alright..heck throw it back together and bleed the system well and see how the lever feels. Look for any leaks. Worst case scenario is you gotta replace it

[chuck hahn]

Hoppes is designed to disolve the powder and copper fouling from gun barrels and is equally as good at disolving the scale and crust in the bores. may swab some more on the worst looking spots and let it sit for a half hour or so to get good action.

[scott]

Hoppes is designed to disolve the powder and copper fouling from gun barrels and is equally as good at disolving the scale and crust in the bores. may swab some more on the worst looking spots and let it sit for a half hour or so to get good action.

It definitely helped - I used it to clean out other parts of the master cylinder, not just the rusted parts. The fumes started to get to me though - I should have used it in a better ventilated area.

Youll probably be alright..heck throw it back together and bleed the system well and see how the lever feels. Look for any leaks. Worst case scenario is you gotta replace it

I assume I should order a new piston/cup set, right? Or do you mean I should try it with the existing one?

I've been waiting to place an order for all the brake parts which includes a piston/cup set for the rear in addition to the various seals, o-rings, etc. I was guessing I'd need either a new piston/cup set for the front or a whole new front master cylinder (which don't seem to be available).