'63 Brake Pedal Slow to Return

[CheezeMan]

Good day all!

I just finished replacing about everything in my brake system, when I discovered that the booster was bad (thanks to all the posts on this forum, I figured that out). I got a rebuild from Booster Dewey and just installed. The very first thing I noticed is that the brake pedal was slow to return to normal position. This was not the case before swapping boosters.

Before installing the booster, I checked the push rod length with the J-21183 gauge and saw it was slightly too long. I didn't adjust it, though, and left it alone thinking that Dewey had it right.

Could the push rod being about 0.1 inch too long cause the slow brake pedal return? Is there a check-valve in the booster that isn't letting air back in to let the pedal return?

Otherwise, the brakes work great.

Thanks.

[RivNut]

I don't know if what you're describing might be the result of mixing power boosters and master cylinders. There are two separate UNINTERCHANGABLE boosters and master cylinders. One system is the Bendix system, the other is the Delco Moraine system. Each system has its own section in the '63 chassis manual. Did the person at Booster Dewey's ask you which one you needed in order to match what you had?

Ed

[CheezeMan]

I don't know if what you're describing might be the result of mixing power boosters and master cylinders. There are two separate UNINTERCHANGABLE boosters and master cylinders. One system is the Bendix system, the other is the Delco Moraine system. Each system has its own section in the '63 chassis manual. Did the person at Booster Dewey's ask you which one you needed in order to match what you had?

Ed

I actually asked that question of Dewey before I bought the unit. He said for '63 there was only 1 booster made. I couldn't find the sections in the service manual you were referring to. The power brake unit starts on page 9-23 in my copy.

I tried some quick experiments and noticed that my pedal will return quickly if not pressed all the way down. I plan to reset the length of the pushrod to factory spec and see if it was the "long pushrod syndrome".

[Jim Cannon]

Chuck, did you replace the 3 flexible brake hoses? Did you replace the brake springs in each drum?

I put a dab of putty on the tip of my booster pin and seated the MC on the booster, then removed it. I used that to estimate the gap between end of rod and MC piston. As long as there is a very small gap there, you are good.

[CheezeMan]

Chuck, did you replace the 3 flexible brake hoses? Did you replace the brake springs in each drum?

I put a dab of putty on the tip of my booster pin and seated the MC on the booster, then removed it. I used that to estimate the gap between end of rod and MC piston. As long as there is a very small gap there, you are good.

Jim, I replaced 3 soft lines, all the hard lines, 4 wheel cylinders, rebuilt the master, installed a new hardware kit at all 4 corners, replaced the vacuum hoses to the booster, replaced the booster, replaced the front shoes and re-surfaced the front drums. The rear shoes were replaced last year and were still good. I did not replace the 2 brass junction blocks. So, pretty much everything was done.

Everything was bleed several times. But I was still not happy with the brakes so took it to an olde time shop. The veteran mechanic there said I did everything right and was even impressed that I didn't do a "hack job" on the lines. He did adjust the shoes more with an old shoe adjuster caliper, and said I might have a hard spot on the drums that cannot be turned out.

I like your suggestion, and may try that. Another one I got from a different forum was to loosen the MC bolts a bit to move the MC out a tad and see if that clears the problem. If so, they said you could simply put a small washer on each stud to give the MC a small gap. But, with this booster, I should be able to adjust the pushrod if necessary.

[JZRIV]

I would definitely call Dewey to discuss your concern. I'm sure he has run into this before.

Pedal return speed should be mostly a function of the spring at the rear section of booster since there is no physical (attachment) connection between the pedal and the master cylinder pushrod. In other words, the pedal will return normally even if the spool and/or pushrod in the MC does not. Since you are using the same MC as before the rebuilt booster, I tend to rule that out as a possibility. I suppose the return spring in the MC may assist the pedal return but again based on what you have said do not think its relative in this case but my opinion is probably irrelative. A call to Dewey should be your next step.

To answer your question about the check valve. With the pedal returned there is vacuum on both sides of the booster diaphram. When you depress the pedal the spool valve (not a check valve) opens the rear side of booster to atmospheric pressure and closes off the vaccum. So on the front side you have vacuum pulling and the rear side you have atmospheric pressure which creates the boost. When the pedal is released the spool returns to close off atmospheric pressure and restore vacuum.

Edited August 31, 2012 by JZRIV (see edit history)

[CheezeMan]

I did call Dewey when I first noticed this problem. His voice mail said he was out on vacation and will return in a couple weeks. :eek: Until then, I was hoping this forum would have something... I did get lots of suggestions here and I'll try 'em out.

Thanks all!

[RivNut]

I don't know if what you're describing might be the result of mixing power boosters and master cylinders. There are two separate UNINTERCHANGABLE boosters and master cylinders. One system is the Bendix system, the other is the Delco Moraine system. Each system has its own section in the '63 chassis manual. Did the person at Booster Dewey's ask you which one you needed in order to match what you had?

Ed

Well here goes, I correct myself. It's in my '66 chassis manual that describes two separate braking system. Section D covers the Delco Moraine system and Section E covers the Bendix system. I guess my thinking goes to goes to advising guys who want to change from a single reservoir system as found on the 1st generation Rivs over to a dual system from a later model to make sure that they match master cylinders and boosters when they make the conversion. Sorry for any confusion that I may have put in your mind. Thanks for making me check it out and squaring myself away.

Ed