Technical 53 Chevy Pedal Firmness Issues

Thanks, everything is tight and its a royal pain to tighten bolts, etc when swapping out the M/C.

I don't think the residual is too close to exhaust? Overall the behavior is just not consistent. I remember a couple times last weekend where the front wheels would feel tighter than other times to turn by hand (when it was on jackstands). I have somewhere around 1/4" spacing (in the M/C bore) before I can hear/feel the push rod actuate the M/C.

Yesterday night I went in the 1 car garage and played with the pedal. When I pumped it a second time it sometimes felt a little harder but not always. Sometimes a couple more pumps would make it just a little firmer but not a whole lot. I never got the pedal to feel really hard. I'll have to see if my friend is willing to let me drive to his place and check things in his driveway. I have a T fitting on the front and a T fitting on the rear. I'm wondering if I should get a 3/8-24 bleeder and disconnect one or two lines at a time to see if I get a harder pedal.

 

... and last weekend I could feelthe wheel was harder to turn by handthan other times and this behavior was sporadic.

Well if the residual is acting up, it would have to change-

FROM
holding zero pressure (why the double pump)

TO

Holding Too much pressure (why the wheels are harder to turn sometimes)

AND

Then Back again.

It Is possible its just gone to holding zero pressure


Sticky caliper slide pins and brake pads stuck in the clips does some really weird stuff and will make you question your sanity.


Air doesn't come and go, - the symptoms are repeatable and predictable given the same situation, time, and cir***stance.

If a MC is acting goofy within itself, the symptoms can change with however the internal seals want to act. Isolating the system and breaking it down into sections is a good basic step to chasing the problem down.

 

Thanks again for your help and suggestions. I'm going to have to ask my friend if I can take it to his drive way one Saturday and go underneath and try to section off the brakes with fittings or plugs until I can trace the problem side.

Some of this behavior was present before I swapped to the 11" disc brake kit. Before I took off the old pinto brakes, I felt the front wheels stuck a little (randomly). I also sometimes felt the pedal stick a bit. For this reason I shortened the push rod slightly thinking that was the issue and maybe it was.

One thing that still makes me wonder is the syringe reverse bleed attempt. I tried to reverse bleed at the p***enger side caliper. I had opened the bleeder to where fluid was leaking out and I connected a nylon hose and a syringe. I couldn't get the syringe to push even with all my strength. I wonder if this points to the residual acting weird. 2psi shouldn't be an issue to overcome with pressure generated from the bore surface area of the syringe. I attempted to change the bleeders for speed bleeders and fluid kept seeping out the threads. I put the old bleeders back on but could have sworn I saw dark circular looking rubber inside of where the bleeder would sit flush. I was way too tired to make anything of it but I wonder if these speedway calipers are supposed to have that? I can't imagine why they would.

 

Just think it thru-
Brake fluid is easy to outsmart. It obeys the laws of physics. Even though you can't see it, it's doing what it's supposed to do no matter what. Now if its not doing what you think or what you want it to should be doing, there is a condition someplace that is making it do what it is. You just gotta figure that out. Something you think is ok isn't as it should be.

Clear as mud right

 

All true stuff. I've got to work my way through it systematically. I'll try to do it at my friend's driveway hopefully with his help.

 

Thanks for your help. After spending a lot of time making it possible to put the front on jackstands I was able to get to work and start isolating the system.

1. I replaced the return spring (I had two in parallel together) with a single one that had a bit more spring constant. This eliminates the two springs potentially interfering/binding up with each other when returning.

2. I checked on the pedal pushrod and notice about 1/4" or less before it engages (when looking from underneath at the pushrod itself. At the pedal itself, I see about 3/4 to 1" movement before it engages with the M/C.

3. I plugged the front M/C port and before I did anything else I tested the pedal. It felt nice and firm and about 1" movement (after it engages with the M/C) before it stopped. This is the exact feel I want. I didn't feel it stick at all.

I replaced the calipers yesterday with replacement ones Speedway sent me and inspected for leaks etc but didn't finish putting it back together because a caliper pin/bolt stripped (I will order a replacement from Speedway). However I took the 2psi residual valve out:

When I blow in from the IN side (the side that goes to the M/C) it blows fine. When I blow in from the OUT side sometimes it would blow with a little more effort and other times not at all. I took the br*** fittings out and saw the following:




I don't ever remember that spring being out like that and I'm pretty sure this residual valve didn't come with the br*** fittings as I had to get them from Pep Boys and use teflon tape. I ruptured the rubber piece a few minutes ago trying to poke it out so I could look at it so I'm ordering a new one. Also I'm positive I didn't have the residual valve installed backwards. I don't see any evidence of heat from exhaust having melted anything inside. To me it looks like the diaphram and spring ***embly pushed itself back some, but I don't know if there is another piece missing that fell out before the br*** fitting goes in.

I think the residual was part of the issue. My other issue with bleeding the front could be slight loops in the lines since I had to hand make them with the NAPA green lines. One other issue is the pushrod does look like it could possibly bind up at very far pedal travel just because of the way the Mustang M/C, mounting bracket, push rod and linkage, and pedal ***embly are all put together. I'm hoping once I put the front back together that pedal travel isn't that far.

If the pedal still feels soft at that point I will use plugs to isolate left to right.

Any advice on other things I should look at?

 

Speedway is sending me a replacement RPV but I don't know if those ones will be robust enough.

 

What a mystery. I got the replacement RPV from Speedway and it has a little plastic piece that holds the spring in.

When I took the fittings off from the old RPV, I did not see this plastic piece in there. Could it have melted? That seems unlikely. I looked on the floor in the garage to see if I could find in case it fell out and it wasn't there.

I'm stumped. Does anyone have ideas? I did not install it backwards either, I checked photos from a few months ago. Also I don't think it would be too close to exhaust, it should be a good 8 inches or more away and tucked on the other side of some frame that would block a bit of the exhaust too. Weird.

 

I should update this in case it is useful for others.

I remember the first residual having something missing inside when I pulled it out.

I put a new residual valve (got a replacement for free from Speedway) last August. Next I insulated it and used a heat shield to keep heat away from it. So far the pedal has not felt soft and not taken the two pumps like before. Heat may have cooked the first one. I also carefully bled the brakes by myself using my hand to reach the pedal ***embly from underneath while stretching my arm to crack the bleeder, etc. The rears I did with speedbleeders.