Booster pushrod length - Team Camaro Tech
Brakes, Suspension & Steering Conversion questions, Steering & Handling

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post #1 of 14 (permalink) Old Sep 30th, 09, 08:44 AM Thread Starter
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Ken
 
Join Date: Oct 2007
Location: St. Louis, MO
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Booster pushrod length

Guys, 25 years ago or more I remember replacing the master cylider on my 69 RS/SS (with PB disks on front.) I probably just used the pushrod that came with the MC but can't remember. I didn't know I needed to check. Immediately afterward I remember the brake pedal position being higher and harder than it was before. At the time I figured that was a good thing.

(Now don't judge me too harshly, remember I hardly ever drove this car…)

I have always had problems with the brakes dragging a bit when hot making a squeek, squeek, squeek as I drove around on my short 20 minute cruises. I never paid it much mind, but this week with the front wheels off the ground I realized the problem is/may be that the front wheels don't spin freely at all—the brakes are dragging slightly all the time.

Now is it even possible to install the longer pushrod if it was designed for a shorter one? Are the brake boosters the same either way? Could I have the correct longer pushrod for the MC but mismatched with the original booster? Before take it apart what do I need to take note of when looking at the booster/MC/pushrod combo when I look inside?

Thanks
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post #2 of 14 (permalink) Old Sep 30th, 09, 07:09 PM
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Steiner
 
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Re: Booster pushrod length

I think you would've known for sure when you tried to put it together if you had the long one in. It should've been long enough that you might not have even been able to get the master cylinder on the booster studs enough to get the nuts started.

You may want to check inside the car first although without putting some pressure on the brake pedal I don't think there is enough force generated to even start to get the brakes to travel. But just the same, go ahead and make sure your return spring is in place and that your clevis on the booster-to-pedal rod is adjusted to give you a slight amount of play between the hard stop for the pedal and brake engagement.

The wheels being difficult to turn could also be the retainer nut tightened too tight on the spindle and too much preload on the wheel bearings. Those nuts really should just be tightened enough so you can't wiggle the front wheels with them off the ground.

The discs will drag a little, so to get the squeak squeak squeak to stop check the parts store and get a little bottle of Disc Brake Quiet. The orange kind in the squeeze bottle works really well. You just take the pads out, squeeze some out on the back of the pads, smear it all over with your finger, let it sit for a minute, then reinstall making sure you have the anti-rattle spring installed correctly on the inside pad. The goo then dries to a rubbery consistency and keeps the metal backing plate on the pads from vibrating/squeaking against the calipers.

If you haven't flushed out your brake system in awhile, it may also be a good idea. Brake fluid attracts moisture pretty easily and once you get some on the system, it will heat up and cause the fluid to expand and can cause your brakes to engage if the fluid gets hot enough. Also, once a bottle brake fluid is opened, it's pretty much useless after a short amount of time on the shelf because it will attract moisture sitting there. I changed mine out to synthetic DOT-4 to raise the boiling point some.

'69 Camaro
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TKO 600-Moser 3.42-Detroit Truetrac
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post #3 of 14 (permalink) Old Sep 30th, 09, 07:32 PM
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Scott
 
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Re: Booster pushrod length

Loosen the MC from the booster and see if the brakes free up. If so pressure is being applied to the calipers. Is the piston on the back of the MC flush or recessed? Flush gets short rod, recessed gets long rod. There is no return spring on power brakes as Steiner stated.
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post #4 of 14 (permalink) Old Sep 30th, 09, 07:41 PM Thread Starter
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Ken
 
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Re: Booster pushrod length

Hmmm… I will check everything you suggested. Sorry to say the fluid has probably never been changed. The only thing that doesn't fit is the fact that I remember the brake pedal position being higher and harder than it was immediately after I changed the MC. Could the pushrod be installed backwards? Are the boosters the same whether for the long rod or short rod? Thanks.
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post #5 of 14 (permalink) Old Sep 30th, 09, 07:51 PM
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Scott
 
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Re: Booster pushrod length

I recently went through this on another site with someone with symptoms similar to yours and the intermediate rod was too long. And a few other minor adjustments. He had a high pedal and the brakes were dragging. Start with my first suggestion and loosen the MC.
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post #6 of 14 (permalink) Old Sep 30th, 09, 07:53 PM
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Steiner
 
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Re: Booster pushrod length

Quote:
Originally Posted by KenFro View Post
Could the pushrod be installed backwards? Are the boosters the same whether for the long rod or short rod? Thanks.
Backwards pushrod...maybe. It is rounded and sits in a cup on the mastercylinder. Putting the flat edge on the cup, if it has a flatter edge on one side, would likely cause about an eighth inch or so of extra length.

I'm not 100% sure on boosters, but I think the short/long rod differences are confined to the master cylinder differences.

If the pedal arm is jammed against the hard stop in the car, you may first try just loosening the jamb nut on the clevis rod inside the car. Then using a pair of pliers, grab it and turn it in some to see if that takes the pedal away from the stop to give you some play. If that gives you some breathing room, Scott's suggestion about loosening the mc from the booster to see if pressure gets relieved is a good one.

'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
500hp/538lbft

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post #7 of 14 (permalink) Old Sep 30th, 09, 08:30 PM Thread Starter
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Ken
 
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Re: Booster pushrod length

You guys are great. One other thing... I've been surfing and researching, and I've seen several posts where guys (talking about Camaros, Novas and Chevelles) recommend adjusting the pushrod. Is that even possible?
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post #8 of 14 (permalink) Old Sep 30th, 09, 08:52 PM
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Steiner
 
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Re: Booster pushrod length

Quote:
Originally Posted by KenFro View Post
You guys are great. One other thing... I've been surfing and researching, and I've seen several posts where guys (talking about Camaros, Novas and Chevelles) recommend adjusting the pushrod. Is that even possible?
They may be talking about the threaded pushrod that goes from the brake pedal to the booster. If everything else is right, it can be a problem if there is no freeplay because the pedal cannot retract all the way back so pressure stays on the master.

To adjust it, you just loosen the jam nut at the clevis on the brake pedal arm and then turn the rod. Screwing it into the clevis will put some slack in, screwing it out will drive the pedal back toward the hard stop. You need a slight amount of play between the hard stop and brake pedal arm. I'm still running a return spring to keep my pedal up against the stop but that's because mine is a convert from manual drums so it had a return spring already there.

'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
500hp/538lbft

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post #9 of 14 (permalink) Old Sep 30th, 09, 09:41 PM Thread Starter
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Ken
 
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Re: Booster pushrod length

All great suggestions. I looked under the dash, I have about 1/16" of "free play" in the pedal before the pedal feels fully engaged. And it only moves an inch or so total. Nothing under there has ever been touched or adjusted. But I'll start there and check everything you all suggested. Thanks to you guys I'm sure I'll find out what's wrong.

I did find this info, but lost the link: The difference between the short (2 5/8") and long (4") rod is 1.375"
The difference between the deep MC (1.35") and the shallow MC (.375") is 0.975"

Now I don't know how much pedal movement there is supposed to be, but I wish I had 1" or so of movement before the brakes are fully engaged. Now I have none. If it's even possible to have a long pushrod and a shallow MC we're talking about losing an inch or so, which is about what all the differences in dimensions noted above are. Hmmm… Just thinking out loud here.

I will post back when I discover what's going on. Thanks again.

(How the heck did I get to be a "Senior Tech?")
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post #10 of 14 (permalink) Old Oct 1st, 09, 09:57 AM
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Ron
 
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Re: Booster pushrod length

Do not over look that that if the Brakes Drag and you get Pad Dust and Spindle Grease leakage that the Callipers may have to be dissembled and cleaned. Rust and Water around the Pistons are the culprit.

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post #11 of 14 (permalink) Old Oct 2nd, 09, 11:53 AM
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Clint
 
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Re: Booster pushrod length

Ken,

I had a similar problem and it ended up being that I put the clevis on the upper hole of the brake pedal. If you have a power booster the clevis should be on the lower hole on the brake pedal and not use a return spring.

Clint
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post #12 of 14 (permalink) Old Oct 2nd, 09, 01:58 PM
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Scott
 
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Re: Booster pushrod length

Quote:
Originally Posted by cwb90 View Post
Ken,

I had a similar problem and it ended up being that I put the clevis on the upper hole of the brake pedal. If you have a power booster the clevis should be on the lower hole on the brake pedal and not use a return spring.

Clint
While that's a common problem, Ken only changed the M.C..
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post #13 of 14 (permalink) Old Jan 1st, 17, 02:53 PM
John
 
Join Date: Jan 2017
Location: Maryland
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Re: Booster pushrod length

Ken,

I am experiencing the same problem. What was your resolution? I am thinking it is the booster rod that goes from the booster to the pedal. I think I have the wrong (longer) one.

Thanks,

John
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post #14 of 14 (permalink) Old Jan 1st, 17, 04:54 PM
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Vince
 
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Re: Booster pushrod length

Are you guys confusing the pushrods? There is a very short pushrod that is in between the MC and the booster. There is another longer pushrod that goes from the booster to the brake pedal. I think the OP is asking about the short pushrod that is in between the MC and booster.


Vince

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