Brake pedal doesn't return all the way after bleeding brakes

[jball1105]

Hey guys. I have Dr. Diff manual disc brakes front and rear. I just bled all the brakes, but when I finished the last caliper (front drivers side) the brake pedal stopped returning all the way and is activating the brake lights. It didn't do this before I tried bleeding the brakes. Any ideas? Thanks

 

[Ron H]

Did you bleed them because installing new rotors/pads? Other brake work you did? One of the things I'd check first with someone pressing the brake pedal is to assure all the pads are moving freely and retracting in the calipers...no binding occurring.

 

[jball1105]

Did you bleed them because installing new rotors/pads? Other brake work you did? One of the things I'd check first with someone pressing the brake pedal is to assure all the pads are moving freely and retracting in the calipers...no binding occurring.

I upgraded to discs front and back and did all new brake lines and new master so it's a whole new system.

 

[pnora]

It is possible that you seated the push rod into the master when you were bleeding. Do the wheels turn freely? If all checks ok you might just need to adjust the switch.

 

[jball1105]

It is possible that you seated the push rod into the master when you were bleeding. Do the wheels turn freely? If all checks ok you might just need to adjust the switch.

The wheels turn freely. Do you mean that the push rod just wasn't seated all the way before and then during the bleeding process it seated all the way?

 

[pnora]

The wheels turn freely. Do you mean that the push rod just wasn't seated all the way before and then during the bleeding process it seated all the way?

Yes. If the pedal is returning so there is no drag that it most likely is working correctly.

 

[VitaminCRR]

I just got done with the same system and finally got it figured out. I assume you changed to the Dr. Diff aluminum master cylinder? If so, you used the adapter plate that goes from four to two bolts attaching the master cylinder. That adapter plate is about a quarter inch thick and the pedal will sit lower because the pushrod is effectively shorter. You can just bend the brake light switch so it hits the pedal and your "lights staying on" problem is solved but if your pedal sitting too low bugs you then you'll need an adjustable master cylinder push rod that brings the pedal back up to stock height. Or you could fabricobble a longer one yourself. I put the adjustable one in mine and now the pedal sits higher, the lights don't stay on anymore and the brake feel is 100% better. Or maybe you don't have any of these issues and I'm just full of ****. Who knows?

 

[jball1105]

I just got done with the same system and finally got it figured out. I assume you changed to the Dr. Diff aluminum master cylinder? If so, you used the adapter plate that goes from four to two bolts attaching the master cylinder. That adapter plate is about a quarter inch thick and the pedal will sit lower because the pushrod is effectively shorter. You can just bend the brake light switch so it hits the pedal and your "lights staying on" problem is solved but if your pedal sitting too low bugs you then you'll need an adjustable master cylinder push rod that brings the pedal back up to stock height. Or you could fabricobble a longer one yourself. I put the adjustable one in mine and now the pedal sits higher, the lights don't stay on anymore and the brake feel is 100% better. Or maybe you don't have any of these issues and I'm just full of ****. Who knows?

Yes I used the Dr. Diff master with the adapter plate. Sounds like this is exactly the situation. Thanks so much! I will adjust the brake light switch and see how it feels with pedal slightly lower.

 

[Ron H]

I had went from manual to power brakes on my '63 plymouth and some of the hassles I encountered had to do with going to power brakes and pedal height adjustment. Well there were a few other things, but ended up machining a new rod pedal rod as the one in the kit was crappy; the brake light switch on my car can be simply adjusted somewhat as the bracket hole is slotted. There's also the matter of the holes in the pedal arm for pedal ratio, one is for manual and other is for power brakes. Ended up with the rod travel setup remaining in the manual rod connection with the rod I made. As for the prop valve, I road tested it to make the adjustment (I left it with rear drums though).

 

[hitparader]

I had went from manual to power brakes on my '63 plymouth and some of the hassles I encountered had to do with going to power brakes and pedal height adjustment. Well there were a few other things, but ended up machining a new rod pedal rod as the one in the kit was crappy; the brake light switch on my car can be simply adjusted somewhat as the bracket hole is slotted. There's also the matter of the holes in the pedal arm for pedal ratio, one is for manual and other is for power brakes. Ended up with the rod travel setup remaining in the manual rod connection with the rod I made. As for the prop valve, I road tested it to make the adjustment (I left it with rear drums though).

I also used the modern aluminum M/C from Dr. Diff on my 64 Polara (factory Kelsey-Hayes booster), and I didn’t need to adjust the brake light switch but pedal travel is very short. I’m switching to the smaller bore m/c, but not much I can do about pushrod length without swapping the booster (I’m thinking about dropping in a dual diaphragm Bendix unit from an Imperial). It’s got a SSBC front disc conversion with factory rear drums.

 

[Ron H]

I also used the modern aluminum M/C from Dr. Diff on my 64 Polara (factory Kelsey-Hayes booster), and I didn’t need to adjust the brake light switch but pedal travel is very short. I’m switching to the smaller bore m/c, but not much I can do about pushrod length without swapping the booster (I’m thinking about dropping in a dual diaphragm Bendix unit from an Imperial). It’s got a SSBC front disc conversion with factory rear drums.

That's what I have, SSBC and initially had hassles with the pedal being way high then readjusting it losing the stroke into the MC. Bought one of those booster rod gauges. The eyebolt in the kit was crappy and bent. The thing looked like one of my high-school metal class projects. A buddy machined a new one for me. Then had a weird pedal sink problem where the brake lights would go on; but with the pedal sunk down it didn't engage the brakes; but with the little remaining pedal travel left I still had good braking. Anyway, by the time it was over I put in another MC and booster. The MC upon bench bleeding it never could get rid of teeny bubbles in one reservoir so got a new one. One of those projects where ya do a bunch of things and never really know exactly what fixed it, lol.