Moparts
All new brakes, low and hard pedal
Posted By: ChallengerGary
All new brakes, low and hard pedal - 01/25/14 03:46 PM
I have a 71 Challenger in the shop that got all new power front disc brakes, lines, etc. We've bled the system and the pedal is low and hard. There hardly seems to be any throw to the pedal. What could be causing this?
Posted By: Supercuda
Re: All new brakes, low and hard pedal - 01/25/14 04:00 PM
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I have a 71 Challenger in the shop that got all new power front disc brakes, lines, etc. We've bled the system and the pedal is low and hard. There hardly seems to be any throw to the pedal. What could be causing this?
All stock parts or not? If not what does it have?
Posted By: ChallengerGary
Re: All new brakes, low and hard pedal - 01/25/14 04:03 PM
claipers and rear brakes are all stock. Stock distribution valve. Some BS little brake booster with what looks like a corvette/GM style master cylinder
Posted By: Supercuda
Re: All new brakes, low and hard pedal - 01/25/14 04:08 PM
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claipers and rear brakes are all stock. Stock distribution valve. Some BS little brake booster with what looks like a corvette/GM style master cylinder
Well, I hesitate to point the finger, but non-stock stuff is where I would look first. Is this a conversion to discs from drums?
Posted By: ChallengerGary
Re: All new brakes, low and hard pedal - 01/25/14 04:16 PM
Not sure if it is a conversion or not. Car came to me in pieces with only rotors - no other brake components whatsoever. Customer supplied parts...
Posted By: AndyF
Re: All new brakes, low and hard pedal - 01/25/14 08:41 PM
Wrong pushrod maybe?
Posted By: ChallengerGary
Re: All new brakes, low and hard pedal - 01/25/14 08:45 PM
That's the first thing i am going to check out - it does not seem to have enough throw.
Posted By: Supercuda
Re: All new brakes, low and hard pedal - 01/25/14 10:27 PM
Let us know.
I hate installing other people's supplied parts almost as much as I hate buying something someone else modified.
Because now you have to figure out why the thing doesn;t work and it may very well be the kit that was supplied, which puts you in the middle of the customer and the supplier, both of which are going to point at you.
Posted By: ChallengerGary
Re: All new brakes, low and hard pedal - 01/25/14 10:51 PM
Exactly - luckily the customer came by today and he actually said it is probably the booster/master that he bought. He got it from eBay and it was some sort of universal deal. I wonder why people do that when they can just go to the auto parts store and order the right thing the first time. I checked and both Car Quest and Advance Auto Parts have the correct booster/master available from Cardone.
Posted By: Kern Dog
Re: All new brakes, low and hard pedal - 01/26/14 08:44 AM
The small booster & Corvette M/C combe seems to be a staple of the aftermarket retrofit brake industry. I was given an 1 1/32" bore Corvette M/C from a guy that ordered a rear disc kit from Master Power brakes. It sucked for non power use due to the large bore.
Posted By: Lefty
Re: All new brakes, low and hard pedal - 01/26/14 09:12 AM
With the engine off, pump the brake pedal 10 times. Push on the brake pedal and start the engine - You should feel the pedal drop under your foot. If not the booster/vacuum source is bad or the MC to Booster interface has a problem.
Posted By: ChallengerGary
Re: All new brakes, low and hard pedal - 01/26/14 09:40 PM
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With the engine off, pump the brake pedal 10 times. Push on the brake pedal and start the engine - You should feel the pedal drop under your foot. If not the booster/vacuum source is bad or the MC to Booster interface has a problem.
It drops a little. The main thing seems to be there is not enough travel in the pedal.
Posted By: hooziewhatsit
Re: All new brakes, low and hard pedal - 01/27/14 05:37 PM
Can you see any daylight between any of the pads and rotors?
If there is, that could be taking up most of your stroke.
Posted By: EV2CUDA
Re: All new brakes, low and hard pedal - 01/28/14 05:23 PM
Push rod in booster too short or linkage at brake pedal too short?
Posted By: ChallengerGary
Re: All new brakes, low and hard pedal - 01/31/14 05:44 PM
Did a bunch of linkage adjusting and also adjusted out the booster push rod - much better, pedal no longer hard but still does not seem right.
Posted By: ChallengerGary
Re: All new brakes, low and hard pedal - 02/03/14 04:20 PM
Well took it for a ride around the block and i am still not happy. The rear brakes seem to lock up first and pedal is still low. WTH!
Posted By: Viol8r
Re: All new brakes, low and hard pedal - 02/04/14 04:28 AM
Assuming the lines are correct coming out of the master!?
Posted By: dangina
Re: All new brakes, low and hard pedal - 02/04/14 06:00 AM
do you have an adjustable valve on the rear line to adjust the rear brakes from overpowering the fronts?
Posted By: ChallengerGary
Re: All new brakes, low and hard pedal - 02/04/14 03:09 PM
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Assuming the lines are correct coming out of the master!?
yes, they are. Checked twice and then checked it again 
Posted By: ChallengerGary
Re: All new brakes, low and hard pedal - 02/04/14 03:10 PM
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do you have an adjustable valve on the rear line to adjust the rear brakes from overpowering the fronts?
Not yet. Guess that is the next step...
Posted By: brads70
Re: All new brakes, low and hard pedal - 02/04/14 03:29 PM
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do you have an adjustable valve on the rear line to adjust the rear brakes from overpowering the fronts?
Not yet. Guess that is the next step...
When I had a drum brake rear I plumbed in a adjustable valve for the rears. I also used the truck wheel cylinders. I never had to use the valve it was always wide open and never had a problem locking up the rears first?
Posted By: dangina
Re: All new brakes, low and hard pedal - 02/05/14 09:11 AM
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do you have an adjustable valve on the rear line to adjust the rear brakes from overpowering the fronts?
Not yet. Guess that is the next step...
When I had a drum brake rear I plumbed in a adjustable valve for the rears. I also used the truck wheel cylinders. I never had to use the valve it was always wide open and never had a problem locking up the rears first?
did you have a front drum setup as well? I have read that the problem lies more on when you have a disk front/drum rear proportioning valve when switching to disk brakes on all 4 corners
Posted By: ntstlgl1970
Re: All new brakes, low and hard pedal - 02/05/14 09:42 AM
Are all the caliper bores and wheel cylinder bores the correct size for that bore of master cylinder? (and what are they) Bendix or Raybestos catalogs used to provide this information. Is the brake light switch adjusted too tight (meaning the pedal cannot fully return) which would have the same affect as the master cylinder pushrod being too long and covering the rear compensating port in the master cylinder which would give a low pedal. As far as the assist goes, I'm wondering if the booster size is too small in diameter. Most of the OE mopar stuff was 10 or 11" if I remember right. Some of the street rod stuff use a small diameter dual diaphragm booster, but it doesn't sound like that is what you have. I can't think of any power brake old mopar with functioning assist that had a hard pedal with the engine running stock. "Squishy" is the term that comes to mind. as far as the rear brakes locking up (if the wheel cylinder bores are matched to the master), are the backing plates grooved? Are the primary shoes (shorter length friction) torwards the front of the car? Are the primary and secondary return springs in the right spots? Are the parking brake cables adjusted too tight?
Did the customer provide any info on how the brakes were before changing all this stuff? (was this a problem prior to changing the booster/master?)
Maybe start by isolating the master - replace one or both lines with a plug(s) and see if the pedal function is correct. we don't have any idea what the original application was for the booster/master on there now other than it came from ebay.
Posted By: brads70
Re: All new brakes, low and hard pedal - 02/05/14 12:59 PM
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do you have an adjustable valve on the rear line to adjust the rear brakes from overpowering the fronts?
Not yet. Guess that is the next step...
When I had a drum brake rear I plumbed in a adjustable valve for the rears. I also used the truck wheel cylinders. I never had to use the valve it was always wide open and never had a problem locking up the rears first?
did you have a front drum setup as well? I have read that the problem lies more on when you have a disk front/drum rear proportioning valve when switching to disk brakes on all 4 corners
I had the 11.75 discs up front and the smaller drums in the back.
10 1/2" I think it is? Cass supplied the 1 1/32 M/C if that helps? I replaced the stock diverter valve/p-valve? with the wildwood adjustable, but never had to use it, ever. Manual brakes , no power assist
Posted By: ChallengerGary
Re: All new brakes, low and hard pedal - 02/05/14 09:05 PM
The biggest problem is the system was pieced together via the internet by the owner. The car originally had front disc brakes. When I got the car, it was missing the booster/master, the brake lines were gone, there were no calipers or brackets (just rotors and 14" wheels), there was no distribution block. Even the firewall plate was missing. He bought the car in pieces and it was missing a TON of stuff. He then went ahead bought a bunch of stuff on eBay and I was tasked to take it from there.
I really think the problem now is the rear brakes are getting too much pressure before the front. An adjustable proportioning valve should remedy that. The pedal height and feel is now livable.
Posted By: ntstlgl1970
Re: All new brakes, low and hard pedal - 02/05/14 09:46 PM
Something else I thought of - is the power brake bellcrank in place in the pedal box??
this is the wrong application, but the right style of component
http://www.ebay.com/itm/MOPAR-75-79-B-BO...2af&vxp=mtr
Posted By: V8val
Re: All new brakes, low and hard pedal - 02/06/14 10:51 AM
Sorry to do my first post here, but it sounds to me like maybe the hole in your brake pedal arm is maybe in the wrong spot? Where the pushrods connects to the arm? An inch up or down can make a huge difference......
Posted By: ChallengerGary
Re: All new brakes, low and hard pedal - 02/06/14 02:42 PM
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Something else I thought of - is the power brake bellcrank in place in the pedal box??
this is the wrong application, but the right style of component
http://www.ebay.com/itm/MOPAR-75-79-B-BO...2af&vxp=mtr
Yes, it's in there.
Posted By: Supercuda
Re: All new brakes, low and hard pedal - 02/06/14 03:22 PM
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Sorry to do my first post here, but it sounds to me like maybe the hole in your brake pedal arm is maybe in the wrong spot? Where the pushrods connects to the arm? An inch up or down can make a huge difference......
Except that's not how Chrysler did it, see the Ebay link.
Posted By: ChallengerGary
Re: All new brakes, low and hard pedal - 02/06/14 04:11 PM
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Sorry to do my first post here, but it sounds to me like maybe the hole in your brake pedal arm is maybe in the wrong spot? Where the pushrods connects to the arm? An inch up or down can make a huge difference......
I will take a look at that - thanks
Posted By: moparpollack
Re: All new brakes, low and hard pedal - 02/07/14 12:08 AM
Those small Chinese brake boosters are complete junk. We have had better luck with small import booster that were used.
Posted By: V8val
Re: All new brakes, low and hard pedal - 02/07/14 08:32 AM
Oh I see, I've only seen a body stuff. Thanks for filling me in. I'm in Australia, all our Chrysler stuff is just a brake pedal with different positioned holes in the arm for different brake set ups.....
Posted By: Supercuda
Re: All new brakes, low and hard pedal - 02/07/14 06:02 PM
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Oh I see, I've only seen a body stuff. Thanks for filling me in. I'm in Australia, all our Chrysler stuff is just a brake pedal with different positioned holes in the arm for different brake set ups.....
Well, maybe Chrysler Australia does it different, but in US A bodies there is a, for lack of a better way to describe it, step down linkage between the firewall and booster to drop the pedal ratio in a power brake setup. In a manual setup the master cylinder just bolts to the firewall with a stiffening plate and different pushrod, same pedal assembly, no extra holes.
Posted By: V8val
Re: All new brakes, low and hard pedal - 02/07/14 10:44 PM
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Oh I see, I've only seen a body stuff. Thanks for filling me in. I'm in Australia, all our Chrysler stuff is just a brake pedal with different positioned holes in the arm for different brake set ups.....
Well, maybe Chrysler Australia does it different, but in US A bodies there is a, for lack of a better way to describe it, step down linkage between the firewall and booster to drop the pedal ratio in a power brake setup. In a manual setup the master cylinder just bolts to the firewall with a stiffening plate and different pushrod, same pedal assembly, no extra holes.
Well there ya go 
Thanks for the explanation 
Posted By: Supercuda
Re: All new brakes, low and hard pedal - 02/07/14 11:38 PM
Well, since y'all got the steering wheel on the wrong side they had to do something. Wouldn't surprise me if they used Holden (GM) sourced parts and I know GM, at least here in the states, does use different holes in the pedal setup.
Posted By: V8val
Re: All new brakes, low and hard pedal - 02/08/14 09:51 PM
Ha ha ha, maybe
