Technical 53 Chevy Pedal Firmness Issues

Hi All,
I'm having an issue with the pedal in my 53 Chevy not feeling firm consistently. Just about every time I pump the second time it firms up. Sometimes randomly it is firmer on the first pump. Other times the pedal feels like it goes in a little further. This is likely trapped air in the system, or could it be a bad Master cylinder?

My 53 Chevy is set up with Mustang II front end and I put the 11" disc brake upgrade from speedway which has GM intermediate calipers, steel braided hoses, etc. The rear end is from a 55' Chevy and I put new wheel cylinders and new shoes recently. I have a 2 psi residual going to the front and a 10psi going to the rear.

The master cylinder is a brand new 69 Mustang power disc/drum. I have it installed underfloor with no booster and a custom linkage that was there from the previous owner.

I have bled the brakes quite a bit. I have speed bleeders in the rear and I did the front myself by using one arm to pull/pump the brakes from underneath and the other to crack the bleeder. I kept doing this until I saw no air bubbles coming out of the bleeder with a hose connected to it.

Could another issue be the pedal push rod? I checked and it doesn't engage the brakes in its resting position. It has two return springs and about 1/8 to 1/4 inch play before I feel it start to push in the M/C bore. Sometimes I randomly noticed the wheels seem to be tight without the pedal engaged. My only other guess is maybe the pin/linkage assembly binding up at a weird angle inside the bore causing the M/C to stay engaged.

Anything I should try? I have until tomorrow before the car goes to a 1 car garage where I won't have much ability to do anything to it. For those of you that are sick of me and my brake threads, this I hope is the last of them. I will be driving the car perhaps once a month to make sure its not sitting and won't be doing any more projects until I find a better place to work on it.

 

Also sometimes it felt a little sticky when the pedal gets firm and releases

 

Also the m/c was bench bled and I have a bit of loops in the brake line routing

 

Sounds like you might still have a little air in the lines. HRP

 

Thanks, I have spend like 10 minutes on each wheel bleeding and gone through a lot of new fluid. I wonder if the loops in my lines (some of them were hand formed) are making it really hard to bleed the air out?

I wonder if I need to take it to a shop that may have a pressurized tool to reverse bleed?

 

One of the biggest causes I have experienced for having to pump to get a good pedal is excessive play in the brake shoe adjustment. If you want to make sure you do not have air your gonna have to vacuum bleed it. I don't care how many times you bleed by pumping vacuum bleeding is more effective.

 

Thanks the new shoes were not arced. I also can hear the drums rub on the shoes when I spin the wheel so I think I had adjusted the star adjusters ok for now. Is it possible with time the shoes will wear in and the pedal will not need to be pumped more than once?

I also feel it stick a little, when it firms up sometimes on releasing I can feel something stick in the pedal and sometimes even have to give a little gas for it to free up.

 

Look for a bind in your pedal linkage too. Disconnect it at the master and see how it feels, look for a hitch in the motion.

 

I did that, the pedal feels fine without the linkage connected to the master. The return springs bring it right back. I think the linkage has an issue but probably inside the bore of the M/C.

It has a swivel joint but i checked and that felt fine throughout the pedal travel.

 

The rod that goes into the master should have a nice radius on it, so alignment can be slightly off and it will still work. The motion of the rod should be as horizontal as possible too. That's all I have!

 

It sounds more like a mechanical issue.
Sticky calipers or worn backing plates that effect shoe adjustment. When all the slop is taken up the pedal is nice. When the slop works its way back in then you need another pump to firm it up.

Backing plates can wear and change the shoe contact pattern, they can cause shoes to hang on one cycle then release on the next. Wear can make your shoes seam tight because they are sitting like a wedge and only the outside very edge is touching .

 

Thanks the rod end is nice and round almost like the stock type pedal push rods I've seen. Supposedly it was an early Eci adaptor that came with the swivel end and threaded rod and some bracket to mount the m/c on the k member.

 

Thanks for your help I appreciate it. It had this behavior with the pinto brakes on the front. I think it started when I had worked on the rear brakes. The front now has new gm intermediate calipers so I don't think the calipers are an issue. I had put new shoes,springs, and new wheel cylinders in the rear and maybe have 100 miles on it since. I seem to remember the backing plates being worn.

What would I do in this instance? Have a shop weld new material and grind flat?

I drove the car this morning to where it will be for the next few months in a 1 car garage. No more taking wheels off unless a shop does it. I did a double pump every time I had to stop and it feels firm and stops a bit better than the old pinto setup. The pedal never felt one bit sticky and didn't have to go in as far. When I don't double pump it feels like the pedal sometimes has to go in farther and sometimes it feels like it sticks there and the behavior is a little less consistent. I can't remember if it's sticky going in or coming out or
Both (geez that sounded dirty . )

 

I also remember some of the backing plate contact points not feeling smooth and a worn in pattern from old shoes. It has a stock 55 Chevy rear end. I notice when I put different length pieces of wood on the pedal that the fronts engage way earlier. I have to push the pedal quite far in to get the rear tight to move by hand. I never tried the double pump when it was on jack stands to see if the rear engaged earlier, and it's too late to try that now.

 

Did ya ever get the master cylinder cap to stop leakin?

 

Do you have residual pressure valves installed?

The backing plate's wear on the pads can easily be built up with weld and ground off. Can do that on the car too.

 

Yes sir! The 69' master cylinder from Napa was far more rugged looking than the Dorman one I had in there before. I had to pry the clip with a big screw driver to get it to go over the humps. No leaking from that lid.

 

Thanks. Yes I have a 2 psi external on the front (a Speedway motors one) and a 10 psi external (a wilwood) one on the rear. I don't know if the M/C I got from Napa for a 69' Mustang has an internal residual. I had bought a special sized 100mL syringe and tried to reverse bleed starting at the calipers and I couldn't push hard enough to force the fluid in and I wanted to avoid a disaster.

I'll have to call around and see if there is any shop that can fix the backing plates or maybe a friend with a welder could help if I'm lucky.

 

If the contact pads are that worn, the shoes get hung up on them and retract very erratically. Put an ad in the classifieds, maybe someone has good ones you can swap in.

 

I fought this issue until I tightened up the brakes on all 4 corners. pedal is nice now and grabs up high.

Before that I also noticed it was better as I pumped it. Was already running residual valves too.

 

Thanks, I remember having seen some groove type wear in some of them when I had put the new shoes on a while ago. Are special tools/skills needed to change the backing plates? I might have better luck finding someone with a welder.

 

How did you tighten it up? The rear shoes were tightened until harder to turn the wheel by hand then I made it looser so you can hear the shoes rub on the drum when you spin it by hand. The front has the new 11" disc kit and the pads are close to the rotors and you can hear the pads rub as you spin the wheels. I bought new ultra premium grade semi metallic pads from Napa and put the cheap looking ones that came with the kit back in the box.

 

The worst part is undoing the e-brake cable where it passes thru, but not a big deal at all. You could buy some time (to rule the problem out) by building up the surfaces with JB Weld and seeing if it makes a difference.

 

Thanks I thought about using jb weld. Now it's in a 1 car garage and can barely move on the sides. I may still try that though. The e-brake/parking cable isn't even connected to the rear end. The previous owner never hooked it up from what I can tell.

 

I forgot to mention sometimes I hear a beep noise for maybe 2 seconds (not a squeel or screech) when I stop usually once the car reaches a full stop. Could that be transmission related and not brake related? I also had this noise before I changed from pinto brakes to the 11" disc kit so if it was brake related it would have to be from the rears.

 

Did you put little dabs of grease on those contact pads when you installed the new shoes?

 

Yes I did. I do remember seeing some groove wear in some of them.

 

I had a similar issue and my residual pressure valve was too close to the exhaust and this cooked the internals, I replaced it and fixed the problem...you can check this by pulling the pressure valve and looking inside it, in my case it was all apart on the inside...

 

That is so interesting and thanks. I had a funny feeling that could also be a potential issue on mine. My 2psi residual is somewhat close to the exhaust and last weekend I could feel the wheel was harder to turn by hand than other times and this behavior was sporadic.

I should have checked the 2 psi residual when I had it on jackstands in my 2 car garage. It's in a 1 car garage now and I'll have to check some time at a friend's place in a driveway.

The purple one in the photos below is the 2psi one. I made a heat shield for the M/C but I didn't think the exhaust came too close to the 2 psi residual. Also the brake lines going forward (not shown in the photo) seemed far enough away from the exhaust.

I had tried to install speed bleeders on the calipers and when I cracked the bleeders open to take them off brake fluid was coming out so there was residual pressure. I didn't use the speed bleeders because the threads were leaking badly at any open position. I then tried to use a 100 mL syringe to force fluid in from the bleeder of each caliper but I couldn't push fluid in because there was way too much resistance. This makes me think the residual was working.

 

I'm a tad claustrophobic and would have moved the whole dealie to a swinging pedal set up. But stick with it, you're making progress & learning.