67t5ponycoupe

It sounds like an adjustment problem on those rear calipers. I would not do anything with proportioning valves or any other kind of valves until you get a pedal back. Adding more stuff is just going to complicate things. The set up you have should be able to give you a pedal. I would try talking to the guys at master power brakes and see if they can help you.

71stang99

No it did not. I was looking through the NPD catalog last night and noticed that they sold one of those. I thought this would be easy as MPB did not advertise needind any valves or additional parts when I ordered. Only in the instructions received did they mention a proportional valve possibly being needed if the rear brakes lock up. I'll post up my results once after I get ahold of the tech line and see where it goes from there. thanks

JMD

A 10 PSI rpv is TOO MUCH for disk drakes, a 3 pound RPV is more in line with what might be used but you should not need one because the m/c is above the brakes on your application. (this applies to disk brakes only)

A PROPORTIONING VALVE WILL NOT improve your pedal, I guarantee this 1000% X 10,000...

You MIGHT end up needing a prop valve, but this has nothing to do with your lack of pedal, and spending time and money adding the prop valve WILL NOT solve your current problem.

You can be about sure that either your m/c is broken or,,,, most likely,,, YOU HAVE AIR IN your system....

Did you check your calipers for bleeders on THE TOP?

If you want to buy something to fix this issue, (which I think would be dumb at this point) buy a new M/C wit a bore size compatible with your brakes.

What kind of calipers does your brake kit use? Are you running a stock m/c?

these details might help some if you have an equipment mismatch, but still, you have air in your system.

Sometimes it is a bitch to get air out. What procedure are you using to bleed your system?

71stang99

The car stock was 4 wheel manual drum. I replaced everything to convert it to a power brake system. Complete spindles/calipers/proportioning valve/power master cylinder with booster/brake switch/power brake pedal assembly and aftermarket slotted/drilled rotors. This was about a year ago. The car has been driven ~500 miles and the brakes worked extremely well.

To match the front I bought this kit from MPB DB1517BHPR (I dont know if that will show up as a link) <http://www.mpbrakes.com/uploads/products/DB1517BR-Installation%20Instructions.pdf> The calipers are supposed to be from an Eldorado Cadillac and the rotors are Trans Am.

Bled the MC by disconnecting the lines at the MC, attached a fitting with hose back into the MC and pumped the pedal until any air bubbles stopped. Reattached the lines and put the lid on the MC, went to the passenger rear, attached a clear hose and catch bottle, let opened the bleed screw 1 turn and had the wife slowly push the pedal all the way down while I held the bottle above the bleed screw. When the pedal was all the way down I closed the bleed screw while she held the pedal down. Did this twice on each side of the rear, bubbles ceased to appear. Went to the front and did the passenger side first then the driver in the same manner. Hardly any bubbles if any showed on the front system. Also I checked the MC between each bleed to make sure that the MC stayed full.

Bleed screws are in the 12 o'clock position with the bleed nipple pointing towards the front of the car:

Perhaps it is the rear brake adjustment but again I thought they were ok as the rear rotors had a slight 'drag' as the instructions mention.

"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."

67t5ponycoupe

Ok this may sound stupid but I'll say it anyway. You can isolate the rear brakes by putting a clamp on the rear flex line going from the body to the axle. If you are will to do that I and then check the pedal it would aleast tell you if the problem is in the rear. It is not great for the flex line but you don't have to leave it on there long. With the line clamped check the pedal. That should help to isolate the problem.

If I were you I would be quickly getting to the point of putting the drums back on.

tx65coupe

I would probably put the rear drums back on. Rear drums are more than adequate for the back.

blue66mustang

If you only pumped the brakes twice for each corner I guarantee you still have air in the lines. There is no way you moved ALL of the fluid and air from the master cylinder all the way to the rear in just two pumps. NO WAY. Bleed them about 10 times at each corner keeping an eye on the fluid level in the M/C. Just refill it from the bottle you use to bleed.

JMD

Bingo!

+1

It does not take much air to make brakes inoperable.

and,


Parking brake adjustment will make NO difference on the way disk brakes are designed to work. Disk brakes are not meant to be adjusted.

And for what it is worth, at this point I would make the disk brakes work, after spending the time and $ putting them on I would not go back to drums only to STILL have air in the system.

71stang99

Update-I finally had a chance to work ont he car and they were bled just fine. The problem was the Ebrake adjustment which has to be setup right for the rear calipers to engage. I ended up doing a search on google for gm brake adjustment and saw a few how to's which were better then the MPB confusion. I still probably have to go back and adjust the Ebrake cable but the 10 mile city drive worked great and the brakes look sharp (painted the calipers blood red to match the front along with matching rotors slotted/drilled. I never did mess with any additional hardware. The cable adjustment appears critical as both calipers keep the adjustment this way when the brake is set. Thanks for the assistance.

67t5ponycoupe

I'm glad you figured it out. The ebrake on the rear disc set up can be a pain because it is had to integrate disc brakes and emergency brakes. Volvo had one of the smartest set ups I have seen. They machined the inside of the rotor to be like a little mini drum. Then they set up a small set of brake shoes in there to set the ebrake. It was completely separate from the disc brake and seemed to work quite well. Again, I'm happy for you.