Setting up a new master cylinder....help, have questions, please read...

Ok, I picked up an '80 Vette MC to use with my large GM calipers front and small GM calipers rear. Everything was going well, I wallowed out the mounting holes so it would fit, sealed up the MC to the Booster fixing the vacuum problem, made up new hardlines from the MC to the distribution block, and started bleeding everything. I let everything gravity bleed for about 30 mins and I was still getting air, so I let it gravity bleed while I ate dinner, checking periodically to make sure the reservoir had fluid. Without using the pump up, hold, release bleeder screw, tighten bleeder screw, let up on pedal and repeat etc process, I believe I've gotten most of the air out of the system. Now here's my questions:

Why is it that when I pump the pedal fluid shoots up from the front reservoir(for the rear brakes)? Having had the stock MC with the plastic reservoir with only one cap, the only time I've noticed fluid shooting up is when compressing the caliper pistons to install new pads. Is this normal or a sign of a bad MC(it is a reman unit)??

Why is it that when I pump the pedal it doesn't build up any pressure and just keeps going to the floor(I would have expected it to get a little firmer with multiple pumps, even if there's a little air in the lines)?

I do admittedly have a small leak in one of the adapters connecting the MC to the distribution block, that I can't seem to tighten for the life of me.

I've got a helper on the way(he just got off work) and we will fix the leak and bleed everything multiple times. I just wanted to know if these are signs of a bad MC before I waste my time bleeding everything? Thanks!

Ary

Did you bench bleed that MC before putting it in ??

bench bleeding will help that problem there is still air in the MC..

Yes, I bench bled the MC. Actually I did it in the rig with my brother pushing the pedal, but I did the whole bench bleeding procedure and it worked. I fixed my small leak and bled the crap out of the brakes and things are back to the way they were with the stock MC except that I've got more pedal left after the rears lock up. Unfortunately I still can't lock up the fronts. I had pulled the o-ring in the proportioning block with the previous setup and now I can't find it. I'm gonna get a new one and hopefully it will push the bias to the front. I also need to play with the pushrod in the booster because I have about an inch of pedal play before it engages the MC.

I think this setup will work, just needs a little tweaking.

Ary

so from what i understand the booster rod is not going allthe way (pushing the full leanth of the MC right) if thats the case then thats why the front arn't locking up...

See Sequoia's E350 M/C install.

-jb :wierd:

DaltonXJ said:

so from what i understand the booster rod is not going allthe way (pushing the full leanth of the MC right) if thats the case then thats why the front arn't locking up...

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I believe SeanP made a new (longer) rod because he had this problem.
Billy

I've seen fluid squirt back up lots of times on MC's. From what I can tell, its just the release of the pressure in the MC. It's never hurt the braking on any vehicles I have worked on.

vintagespeed said:

See Sequoia's E350 M/C install.

-jb :wierd:

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Got a link? I didn't see it.

I've been driving it all day and it does stop better than with the stock MC. With the stock MC only the rears really did anything and they locked up almost immediately under paniced braking. With the 'vette MC and no further adjustments to the prop valve or pushrod I'm definately getting more front braking. I'm expecting a big improvement with the return of the o-ring which I will do tomorrow.

I've also been discussing this with SeanP as we're both at the same point and we're kinda keeping eachother posted on any interesting developments.

Thanks!

Ary

Ary, at least you have pedal. I have run about a quart of fluid thru the system and I still cannot get pedal that is suffiecient. I know my pushrod is good, I have about 1/4" of pedal travel before the rod hits the MC plunger. My only conclusion at this point is that I have got a bad MC. Mine is a remanned, not new and I have seen posts that folks have said they got bad MC's out of the box.

SeanP

Don't you have a '97+ XJ? What was wrong with the stock system? I'm running a D44 front and GM discs rear and the braking is absolutely perfect. Stopping power is excellent (on 34's), pedal travel is perfect, and front to rear balance is so optimal I've never been able to lock up one set over the other.

Just curious what got you to make a change (or pull that o-ring in the first place)?

Nay

Yes, I have a 97 (assuming you were directing this ? towards me). I have a front ford D60 with 1 ton dual piston calipers and a hybrid rear axle with 3/4 ton Chevy single piston. The stock MC doesn't move enough fluid for my set up.

SeanP

Nay said:

Don't you have a '97+ XJ? What was wrong with the stock system? I'm running a D44 front and GM discs rear and the braking is absolutely perfect. Stopping power is excellent (on 34's), pedal travel is perfect, and front to rear balance is so optimal I've never been able to lock up one set over the other.

Just curious what got you to make a change (or pull that o-ring in the first place)?

Nay

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Nay said:

Don't you have a '97+ XJ? What was wrong with the stock system? I'm running a D44 front and GM discs rear and the braking is absolutely perfect. Stopping power is excellent (on 34's), pedal travel is perfect, and front to rear balance is so optimal I've never been able to lock up one set over the other.

Just curious what got you to make a change (or pull that o-ring in the first place)?

Nay

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I couldn't stop :moon:

I could stand on the pedal with both feet and it wouldn't even think about locking up. I know that locking up doesn't provide optimal braking, but it was just downright sh!tty. As I get used to the 'vette MC I'm liking it more and more. I don't have to push as hard as I used to even when I was stock, like 28" tires stock, and I think once I get the o-ring in the bias problem will be fixed.

Ary

P.S. The o-ring is not a seperately available thing from the dealership. You have to buy the whole freakin prop. valve to the tune of $90. So I'm gonna go by the parts house on the way home and see if I can't find an o-ring that will work.

Ary, just get the summit proportioning valve for $40.

SeanP

SeanP said:

Ary, just get the summit proportioning valve for $40.

SeanP

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For the 20 mins it'll take to go to the parts store, sort through the bin of o-rings and find one that'll work and the $.50 it'll cost me, I'm gonna try that route first. The little odds and ends on this project have really added up and I'm BROKE, so $40 is a lot of money for me right now.

Ary

Safari Ary said:

I couldn't stop :moon:

I could stand on the pedal with both feet and it wouldn't even think about locking up. I know that locking up doesn't provide optimal braking, but it was just downright sh!tty. As I get used to the 'vette MC I'm liking it more and more. I don't have to push as hard as I used to even when I was stock, like 28" tires stock, and I think once I get the o-ring in the bias problem will be fixed.

Ary

P.S. The o-ring is not a seperately available thing from the dealership. You have to buy the whole freakin prop. valve to the tune of $90. So I'm gonna go by the parts house on the way home and see if I can't find an o-ring that will work.

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Strange. I had the opposite problem with my D30 and 8.25 drums. It would lock up on loose gravel at the slightest pressure, but just wouldn't stop on regular pavement. Now I don't have the loose gravel problem (within reasonable pedal pressure) and it stops hard on the street.

It's rare that I don't have the worst side effects of any given mod. I think that you have actually taken over that reign from me these days. My 8.25 was clearly cursed, and you bought parts from it and took the curse. Thanks, man .

Nay

Nay said:

Strange. I had the opposite problem with my D30 and 8.25 drums. It would lock up on loose gravel at the slightest pressure, but just wouldn't stop on regular pavement. Now I don't have the loose gravel problem (within reasonable pedal pressure) and it stops hard on the street.

It's rare that I don't have the worst side effects of any given mod. I think that you have actually taken over that reign from me these days. My 8.25 was clearly cursed, and you bought parts from it and took the curse. Thanks, man .

Nay

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LMAO, hopefully I won't pass the curse on to the next owner of those parts. The strangest thing is that occasionally I get EXCELLENT braking when it's raining or otherwise moist outside. I had attributed this to slight surface rust developing on the rotors and creating this temporary effect. However it seems to last as long as it's wet outside, but if I stop and shut her down for a couple hours the brakes are back to normal. I can't figure it out.

Ary

Safari Ary said:

For the 20 mins it'll take to go to the parts store, sort through the bin of o-rings and find one that'll work and the $.50 it'll cost me, I'm gonna try that route first. The little odds and ends on this project have really added up and I'm BROKE, so $40 is a lot of money for me right now.

Ary

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It is not just a O ring. It is actually a cup and if you put it in the wrong way the rears will not work at all. That shows you to that it is not a o ring. It is designed to stop fluid in one direction only so you should go to a brake place and find one there. I take it that in the States it is the same as here when I worked in a brake place that those sort of things are kept in stock so you could re-build wheel cylinders, M/C and calipers etc.?

Gojeep said:

It is not just a O ring. It is actually a cup and if you put it in the wrong way the rears will not work at all. That shows you to that it is not a o ring. It is designed to stop fluid in one direction only so you should go to a brake place and find one there. I take it that in the States it is the same as here when I worked in a brake place that those sort of things are kept in stock so you could re-build wheel cylinders, M/C and calipers etc.?

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Thanks for pointing that out, I wasn't aware. I guess I'll go buy the junkyard since they just got a '98 in and rob the "o-ring" from that one.

Ary