Topic: Help with rear disc brakes!!

[mattblack84]

my 79 trans am has been sitting for a while and i finally got it back from the body guy and am going through the car slowly what are my best approaches for repairing the rear brakes there is no leaks but there def not grabbing and i was thinking new pads and rotors but isn't there somthing with the calipers on these i'm looking at the service manual and am a little confused any help would be greatly appriciated!!

[Tin Indians Rule]

I'm going to hold off responding and see if Evan jumps in here. I know he just went through the wringer with his so I'll see if he or others pony up advice first.

[mattblack84]

well let me know so I can get my baby fixed!!!

[eroc022]

yup, these are a headache.... they have to be so accurately set with the emergency brake in order to get a good pedal feel...  I think Renovations has the link or pdf file that describes how to do it the best... its in the service manual as well... basically you will have to get the emergency brake as close as possible to engaging then you can bleed the brakes normally, to get the emergency brake set right you have to take off the inside lever and manually adjust the depth that the inside pad sits... by turning the shaft clockwise or counterclockwise the pad will move in and out... get it to where it touches the pad, and then just barely back it off of it so you have no drag.... then reinstall the lever, and bleed the brakes as normal... new pads and rotors are always a good idea too.....

[jjr]

 From what I've seen and experienced the rear calipers are kinda
suspectable to corrosion from "not" using the parking brake every
time.

 Most folks buy rebuilt units rather than to do them themselves.

 You have to follow the very detailed instructions on setting them
up correctly, something I have to review each time I do a set.

 The rear discs work both by fluid and by mechanical means and so
setup is special.

 You'll need a few tools, a special one to be able to get the piston
at the proper depth, do you know which one I mean?

 Then there is a trick to the bleeding, if you aren't careful you
may create a difference in system pressures and trip the proportioning
valve to lock out one or the other system (front/back). Often the
old friend in the car pumping the pedal procedure does this.

 How where you planning on bleeding the system?

 Joe

 

[eroc022]

Joe, I reverse bled my system by feeding the fluid in through the caliper into the master cylinder... no air is in the system, but yet I still have a horrible pedal feel... whats the trick for the rest of it? its about to just go to the shop...

[jjr]

 While I love and have used the reverse method, it's not 100% either.

 The thing that works is a obscure tool that holds the end of the pin
on the prop valve in place keeping the shuttle from moving. On the
aftermarket valves, a temp replacement for the differential switch
has a solid tip that prevents the shuttle from moving.

 Have you seen this?

 Joe

[eroc022]

my disc brake valve doesnt have a pin on the end..... solid brass but I do know what you are speaking of....

[kc79ta]

Joe, I reverse bled my system by feeding the fluid in through the caliper into the master cylinder... no air is in the system, but yet I still have a horrible pedal feel... whats the trick for the rest of it? its about to just go to the shop...

Eroc, That might be your problem. Unless you pulled the MC back off and bench bled it after. I no pro on brakes, but I remember hearing that reverse bleeding a system with a tipped back MC can trap air in it that can only be bled out with it level on a bench. Just a thought before you spend some $$$ at the shop.

[jjr]

 The brass one... then:



 Joe

[eroc022]

aha well I found out I have a leak somewhere too. front brake resivoir is much much lower now than when I did this... I think its all coming off and hydroboost is going on.....

[mattblack84]

well i found out today it is my rear calipers no adjusting, the screw moves a little i'm thinking i might be able to fre them up been spraying pb blaster and working the ebrake.

[mattblack84]

Well got the e-brake to move every thing there ok, but the levers in the calipers themselves don't want to move much should i rebuild or try and free them up?

[eroc022]

They shouldn't move much except for to clamp down on the rotor..... Very tight tolerance with them

[mattblack84]

ok but how do u get the piston to come out so i can put it against the rotor?