Thread: Brake troubles

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Ok guys I worked on the brakes today, no good results. This is what I did.

1. disconnected front brake line to isolate rear brakes. The high hard pedal disappeared.
2. tried brake no good
3. bled the stuffing out of them
4. tried brake no good, just slows the wheels
5. put a New ( not rebuilt) Master cyl. (1980 corvette disc/disc 1.125 bore) on by passed all valves bled them to death and tried the brakes, no good again
6. moved rear brake line from rear reservoir to front reservoir by passing all valves. no good again
7. tried emergency brakes they didn't stop the wheels either and I can't pull any harder on the handle. This is very baffling, the arms on the calipers only move about 1/4 - 3/8" and the wheels can't be turned by hand, under power @ idle they turn with no problem. The same arms when no brake pads are in place will move 1.5 inches.
8. Took a bunch of pictures to show you.

The rod going into booster moves about 2 inches in when bleeding the system.
With the valves closed and the front lines connected the rod only moves about 3/4".
With just the back brakes connected the rod moves about 1-1.25".
Very solid stream of fluid during bleeding.

I have the same rear brake calipers, I remembered something "specific" to the installation, here it is off MPB instructions, give this a try and let us know.
WARNING
FOR YOUR REAR BRAKES TO OPERATE
YOU MUST ADJUST THE REAR CALIPERS
When installing rear disc brakes with calipers that have an internal parking brake you must adjust or set the calipers
when installing. Failure to do so will prevent you from getting a firm pedal and you will have no rear brake function. You
must also set the parking brake every time you park to keep the calipers adjusted.
The caliper piston is adjusted outward by turning the nut on the lever or by cranking the lever. This ratchets the caliper
piston outward moving the pads closer to the rotor. If you do not do this the rear calipers will take up brake fluid but the
pads will never squeeze the rotor sending the pedal to the floor.
Only peform this adjustment with the caliper and rotor installed on the car. Start by spinning the rotor. Crank the lever
and spin the rotor again to see if there is any drag. Continue cranking the lever until there is a slight drag on the rotor.
Attach the parking brake cable. The caliper should now be adjusted. Repeat on the other side
"One of the biggest advantages of a disc type brake is that it has a fool proof self adjuster. Not so with the rear disc GM! The
rear calipers adjust off of the parking brake. The parking brake is incorporated into the caliper. You MUST set the parking
brake every time you park your car! Not many people do that nowadays because it is much easier to just put the transmission
in park and walk away! The rear caliper pistons utilize a "one way clutch" or "sprag" inside the caliper piston. When the
parking brake is applied the sprag senses when there is .030 or more clearance between the friction material on the inboard
side. When the distance is at least .030, the sprag turns inside the piston adjusting it out and keeping the rear brakes adjusted.
If you are not setting your parking brake with this setup EVERY time you park your car then two things will happen. #1 -
You will start to lose service brake pedal. #2 - The sprag will seize on the inside of the piston and will never work again.
NEVER buy these calipers from a rebuilder, because rebuilders use the old piston in most cases and the piston is the reason
the calipers were changed to begin with! Master Power Brakes uses only NEW calipers for this application! Also, when
replacing rear pads on these calipers, GM says to "get into the vehicle after you have installed the pads and apply the parking
brake 60 times". The short cut around this is to adjust the brakes out by unhooking the parking brake cable at the lever
and adjusting the pistons out using the parking brake lever and a .030 feeler gauge between the inboard pad and the rotor.
Then get in the vehicle and pump the parking brake 2-3 times."
Detailed instructions at http://www.mpbrakes.com/docs/orig-gu...STRUCTIONS.pdf

Matthyj Thanks for the info. I had done all those things in the past and tried them again today to no avail.
I bought a power bleeder also and bled the system 3 times with it. I put my 7" power booster on to see if that made difference, no difference. The calipers seem to function but just not enough pressure on the rotor.
With emergency brakes applied it still does not stop the wheels, I can't pull any harder on the lever.
Maybe some other type calipers ?

What does the caliper manufacturer say about it?

Navy, I've gotta admit when I read that set of instructions that Matt posted I was thinking that he'd hit a home run! I'm still not sure he hasn't, and I'm leaning towards the #2 result of not using the e-brake regularly: [QUOTE-Matthyj]#2 - The sprag will seize on the inside of the piston and will never work again.[/QUOTE]

I'm wondering if the sprag has not seized in your rear calipers. I think I'd be on the phone to Master Power Brakes to chat with them. Your symptoms seem to fit the description Matt gave to a T.
(I was typing at the same time 36Sedan was - we're on the same page!)

Originally Posted by rspears

Navy, I've gotta admit when I read that set of instructions that Matt posted I was thinking that he'd hit a home run! I'm still not sure he hasn't, and I'm leaning towards the #2 result of not using the e-brake regularly: [QUOTE-Matthyj]#2 - The sprag will seize on the inside of the piston and will never work again.

I'm wondering if the sprag has not seized in your rear calipers. I think I'd be on the phone to Master Power Brakes to chat with them. Your symptoms seem to fit the description Matt gave to a T.
(I was typing at the same time 36Sedan was - we're on the same page!)[/QUOTE]

The caliper works fine as far as the sprag thing goes. If I take a pad out and work the lever the piston comes out as is should, then I have to turn/screw in back down to allow the pad to be put back in place.
This brake kit came from Speedway but now I'm thinking I should have just spent an extra 300 and bought Wildwood with the disc with emergency drum brake set up.
This is what I should have bought to start with and I'd be done, I think. http://www.speedwaymotors.com/Wilwoo...set,34503.html

The whole darn thing to just very perplexing not to mention the time spent and I'm sure more money is sure to leave my pocket before this is over. Its just about got me %issed off.

Sometimes we just can't help ourselves. A while back I bought a couple of phenolic spacers (cheap off ebay) to keep my carbs from percolating the fuel out. I went to put them on today, removed both carbs, prepped everything, ready to go, spacers don't fit my manifold????? They said they would fit my carbs, which they will using the outer stud holes, problem, my manifold uses the inner stud holes.
The cheap becomes expensive, lol!

In post #8 on 12-24, I posted about those calibers being------and to get an OEM manual about the service/adjustment of them.
Do you have them on the correct side of the rear end? that is just as important with those adjusters as is the issue of the bleeder screws being on top----

and are the rotors the correct thickness for the vehicle the calipers are speced for????

Originally Posted by 36 sedan

The cheap becomes expensive, lol!

Boy, you hit home with saying that, sometimes I feel like I am the Lone Ranger in the rodding world with this scenario, this forum shows I am par for the coarse!
Navy, I wanted to let you know also that that the brake manufactures now claim there is a difference in a parking brake & a emergency brake, simply put a parking brake will hold the car from a stop in neutral, a emergency brake is for emergencys, sounds like its a play on words to sell something of lesser function & quality, but almost all manufacturers call them parking brakes now. I am thinking the same thing, the sprag is stuck swap a front caliper and a rear caliper (don't worry about the cable) and see if the fronts work on the rear, they have the same bolt spacing if I remember correctly.

Originally Posted by jerry clayton

In post #8 on 12-24, I posted about those calibers being------and to get an OEM manual about the service/adjustment of them.
Do you have them on the correct side of the rear end? that is just as important with those adjusters as is the issue of the bleeder screws being on top----

and are the rotors the correct thickness for the vehicle the calipers are speced for????

Jerry: Thanks for the in puts. The calipers can only go on one side and keep the bleeder on top so I'm thinking they have to be right. As for thickness the piston can move out a bunch and its all new so I'm thinking all is of right size ?

Originally Posted by Matthyj

Boy, you hit home with saying that, sometimes I feel like I am the Lone Ranger in the rodding world with this scenario, this forum shows I am par for the coarse!
Navy, I wanted to let you know also that that the brake manufactures now claim there is a difference in a parking brake & a emergency brake, simply put a parking brake will hold the car from a stop in neutral, a emergency brake is for emergencys, sounds like its a play on words to sell something of lesser function & quality, but almost all manufacturers call them parking brakes now. I am thinking the same thing, the sprag is stuck swap a front caliper and a rear caliper (don't worry about the cable) and see if the fronts work on the rear, they have the same bolt spacing if I remember correctly.

Yup I was going to try that but ran out of steam . The calipers are supposed to be emergency type according to the listing.

Originally Posted by Matthyj

Navy, I wanted to let you know also that that the brake manufactures now claim there is a difference in a parking brake & a emergency brake, simply put a parking brake will hold the car from a stop in neutral, a emergency brake is for emergencys, sounds like its a play on words to sell something of lesser function & quality, but almost all manufacturers call them parking brakes now. .

NAVY, I've got that Wilwood kit in mine, the "parking" or "emergency" brake is basically worthless! It won't hold the car on a hill and even if it's "on / engaged".. you can drive right over it without knowing it. I've done it a couple times so now I don't bother setting it.

I even added short pieces of metal to increase the leverage and it isn't much better.

More testing today. The e-brake arm on the caliper is only moving 1/4 to 3/8 when brake is set.
I removed the brake pad from piston side and moved the E-arm 3/8 to 7/16" dozens of times and no piston advancement, moved out but right back in when arm was released .
Moved the arm a full stroke 1 -1.5" and piston did advance. Whats this mean ? I wish I knew . Still can't understand the lack of stopping power when stepping on the brakes, only .015" gap between pad and rotor when brakes are off/at rest.
Does one side of the Master cyl.affect the other, I've been trying to work just one side of the cyl. so the front doesn't give me false high hard pedal. mumm ?

Yes it does-thats why oem setups have that combo valve thingie-dingie-------and your pad probably isn't setting on the piston at the .015 -------piston is retracted into the housing

You might want to look at rear brake package Ford Motorsports sells for rear disc around $300 complete just like what is on Explorer rears------

As I said earlier, I have the Explorer brake setup on my 46. Brakes work fine and the parking/emergency brake will hold the car in gear (NSRA Safety 23 test).