I have a 79 trans am with rear disc brakes. I replaced the back calipers to get the e brake working. I decided the system was due to be replaced and replaced the entire system front to back stainless lines New master, booster, calipers, proportioning valve, brake hoses……. all of it. the pedal sinks to the floor. I can’t find any leaks I verified the power booster has good clearance on the master cylinder I bled the brakes with a helper Bled the brakes with a pressure bleeder we’ve bled them about 6 times. when I push the brake pedal down. With the car off. The pressure holds. It doesn’t go to the floor. It goes halfway down. when I turn the car on. The power booster helps the brakes. The brakes go to the floor. if there’s air in there. I can’t find it or get rid of it I checked the proportioning valve. Put the tool in it. It’s not wet under the switch I set the pressure bleeder up. It lost 1 psi in 20 minutes. Could have been from the pressure bleeder to master cylinder adapter. I know the pedal is not supposed to go that far down. it stops the car at the end of the travel. But it’s dangerous and way too far. there is only 1 bolt for the pedal. I cannot figure out why there is so much pedal travel before it stops the car. I’m thinking about plugging the master cylinder to see if that changes anything I’m thinking about bleeding it at every connection the calipers move freely. the brake pads are new. I’m about to take it to someone else. I don’t even know what advice can be had that I haven’t done.
Did the system work properly after replaced the rear calipers, but before you replaced everything else? I usually suspect those funky calipers with parking brakes in them, first...either not adjusted, or air in them, or defective.. you made sure all bleeder screws are at the top of the calipers?
New = untested, not perfect. Disconnect and block off the line out to the rear. Test. Reconnect the rear, and disconnect and block the front. Retest.
As much as I love to rag on those calipers, I don't believe they are your issue. That particular MC is a bit of a ***** to bench bleed. Lots of areas for air bubbles to get trapped. If you try to bench bleed it in car, nose up, you will never get the bubbles out. On this MC the compensate port on the rear traps a lot of air bubbles and needs some serious persuasion. After initial bleeding there was still air trapped at the rear compensate port. Pushing the piston in a mm and releasing did help free more bubbles but this trick only worked for so long. Tapping with a hammer helped In the end, used a clean straight pick to persuade the rest of the air bubbles from the compensate port. Was pretty close to dis***embling the whole MC just to verify it was not a faulty seal. It was that difficult to bleed. Brakes are still solid on that car.
FWIW. There are three different MCs for this F bod. Manual Brakes 1" bore Power Brakes 1- ⅛" bore 4 Wheel disc 1- ⅛" bore Dunno. Tried bleeding like it would be mounted, on a vise, but that was just too much work. Forward piston/circuit bled pretty quick, rear piston/circuit bled normally, it was just the rear compensate port had quite a bit of air trapped and was not being cooperative.
The Jalopy Journal
