At my wits end, hoping anyone here can help with advice. I've been trying to rebuild the rear calipers on my 85 Trans Am. Bought the upgrade kit from the dealer for new pistons, complete seals, and beefier springs for the emergency brake.

My problem: I cannot get a good seal around the emergency brake actuator screw that extends past the rear of the piston. Getting fluid leaking out no matter how many times I disassemble, try new seal etc. Must be some key part I'm missing?

Been using the disk brake caliper tool from OReilly's rental program, have tried pressing the piston fully into the bore, screwing it in, etc.

Any help would be MUCH appreciated. Been screwing around with these since October.

Thanks for any tips!
Matt

 

I never took mine apart but once the Piston is in have you unscrewed the parking brake actuator screw to get the sealing surface past the seal lip?
also if you want pm me your email address I can send you photos of the caliper rebuild instructions from my '88 shop manual.
Dave

 

How much of a leak? It is normal during adjustment procedures to have a little fluid to come out. When you put your actuators back on, there is another seal/washer that they hold against the back of the caliper that helps seal around the bolt. It shouldn't be a lot and shouldn't run out from depressing the pedal if your actuator arms are on.

 

Thanks for the offer! I have an 85 manual that has been getting a lot of use!

Honestly, it has altered between little leaks and big ones. I've had each caliper apart a couple of times. Currently, I think the passenger side is ok, but cannot fully bleed it out and test with driver side leaking as badly as it does.

Does the parking brake need to be adjusted first before trying to seal and fully bleed out the brakes? I have been trying to get the brakes bled first, then was going to tackle the parking brake.

 

These Parking Brakes are a PITA. If you look at how everything needs to be set up for them to work, I don't know how you separate the two TBH. When installing the calipers, the pads need to be set to very close to the rotor, I actually set mine where they seemed to just kiss on the rotor. Then proceeded to get my brackets set in place. Knowing that a little fluid may seep, I figured a little air may get in. So, I got all of mine set before I started bleeding and confirmed parking brake functionality. I don't think there is a technical reason you can't, but it may cause you to need to re-bleed. I actually pumped mine up and applied as much force to the pedal as I could, pulled the parking brake as hard as I could, and then bled mine to get the last little bit of air out. I guess I thought of it this way, if the parking brake doesn't work I would have had to remove them again to figure it out, so might as well confirm function before bleeding. Though, I will say adjusting out the equalizer bar and removing/installing the springs on the arms multiple times is also a PITA. Basically, these brakes are a PITA

I had some stubborn air in both fronts and rears when I re-did mine and had to bleed them a few times to flush all the old fluid and get all the air out. Keep in mind mine got a new MC, braided lines and proportioning spring while I was at it. Also, on a tip from Daferris above, I actually gravity bleed mine at each corner to fill them before I started trying to get "ALL" the air out. Eventually it ended up being gravity to fill, vacuum, and then the two man method on the front until I had the pedal feel I wanted.

Can you post a picture of how much leakage you are getting? I don't think I ever tried to actuate mine without the actuator arms installed. Possibly, you could just install your arms so the nut will hold the arms and seals against the adjusting screw to caliper body and see if that seals it up.

 

Thanks for all the info! I will work on the parking brake to get it adjusted in, then try bleeding again. My cables are fairly tight, as that was part of my rear brake rebuild (new cables on both sides). I've been bleeding with the actuator arms installed as well. Sounds like I might need to work the parking brake lever a few times first.

These brakes have been a challenge for sure! I've never struggled so much to rebuild a set of calipers, but I think this is the only set i have done with this style of parking brake integration. Hopefully my last!

 

I will admit I swapped out mine for LS1 rears when I put in the 10 bolt so I had a better choice of gears than the 2:77's it had new.
i really don't miss the old iron calipers either

 

Progress today. After reviewing the assembly manual pictures, I realized I had installed the thrust washer in the wrong order. I put it on top of the piston then screwed in the actuator. WRONG! No wonder the o-rings weren't sealing and keeping fluid out. After reassembling both calipers, I've got them bled but managed to suck air into the master cylinder. D'oh! Have that to deal with now. Fingers crossed.

Wrong. Thrust washer between actuator screw and piston.

Right. Thrust washer seals between acutator screw and caliper housing.

 

Yup, I can see that being a problem.

You have to remove and bench bleed the MC on these cars, which means and entire system bleed following. Been there, done that.