Brake Bleeding

[sourpwr]

Originally Posted by TeamRush

Now I screw the pistons OUT to take up most of the slack before I put the caliper/pads on the rotor!
Saves a TON of time on the E-brake handle or pedal!

I ended up using some long handled pliers and cycling the e-brake lever at the caliper several times to tighten them up.

Originally Posted by CJ7Taz

Thinking of this, sourpwr, was the peg on the back of the pad in the hole in the puck on yours? If not that would be enough to cause the caliper to cock when the brakes are applied and bind on the pins.

You said you can see a twist and I took that to mean end to end across the top of the bracket. Maybe you just meant the bracket was flexing.

What did your worn pads look like? Was one end worn more than the other or was the top edge worn more than the bottom?

I'm pretty sure that the peg on the pad was lined up properly with the recess in the caliper piston. The pad was evenly worn front to back and top to bottom. Just not inside to outside.

I'm pretty sure that it was the bracket flexing which looked like a twist.

The calipers really are a pain to get back to "normal" for new pads. I ended up using large channel locks gripping the top edge of the piston. It took several attempts to get the peg lined up properly. Rotate the piston, then cycle the ebrake lever.

It was very difficult to find new pads to go into these calipers. Neither NAPA nor Advanced listed rear pads for a '76 caddy. They both tried to sell me the "metric" pads. Advanced had them listed but, I don't know if it was a manufacturing error or what, but the inner pad did not have the peg. Heck, it did not even have the top half of the backing metal. I ended up finding pads at the new joint in town, I forget the name.

I also found out that the local NAPAs are no longer accepting used oil. Apparently they were paying hefty fees because the used oil was contaminated.

-- mike

[sourpwr]

I now have a more plausible explanation as to why the pads wore unevenly.

I'm still running 15" rims. I have ground all (4) calipers to increase clearance. However, you can see the wear marks on this rim that indicate interference between the caliper and the rim. I venture that with a little dirt and mud thrown in to the mix that could keep the caliper from releasing properly.

-- mike

[sourpwr]

I picked up a '73 Corvette Master for power brakes last week. I spend the day today installing it. I think that it took all of 5 hours to do. I still want/need to replace/remove my combination valve at some point. However, in order to do that I will need to replace all of my brake lines as the ones entering and leaving the combo valve are in pretty bad shape.

So here are a few pictures.

The first is the brake booster.

The second is the non-adjustable plunger.

The third is the back of the Jeep master

The forth is the back of the Corvette master with my high tech plunger extension. The Corvette master had a much deeper "hole" than the Jeep master. I needed to make up about 1.4 inches. So I took a 1.5 inch bolt and cut it down to so that I had the correct lenght. Unfortunately, I cut about 0.1 inch more than needed.

The fifth picture is my bench bleed setup. The new master was pretty neat with the bleeder screws. I bleed in in the vise for a bit, then put it in the Jeep and bleed it some more before hooking up the brake lines.

The sixth picture is the routing of the brake lines so that they could reach the correct holes in the master. The Jeep and Corvette master have the holes reversed.

I ended up bleeding all four corners three times, then took it for a spin. The peddle does not go all the way to the floor anymore, which is what I wanted. I only tried stopping from 25 mph to 0, but it did feel more responsive.

-- mike

[sourpwr]

Last one.

When I took the wheels off, I could see where the caliper was scrubbing the wheel still. I still need to clearance the calipers further or step up to a bigger rim/wheel combination -- you know what I want to do...

-- mike

[TeamRush]

Originally Posted by sourpwr

I ended up using some long handled pliers and cycling the e-brake lever at the caliper several times to tighten them up.

Wish I would have though of that ahead of time...
Instead of masturbating an E-brake handle until I had tennis elbow!

[IN2DEEP]

Glad you got the brakes working better....... but shouldn't the brakes be WORSE with this new (larger bore) master cylinder?

All the math and theories in this post seem to say your pedal should go to the floor a lot easier than with the old master cylinder.........

[CJ7Taz]

Originally Posted by IN2DEEP

All the math and theories in this post seem to say your pedal should go to the floor a lot easier than with the old master cylinder.........

Nope, bigger bore means more fluid moves so the pedal wouldn’t go as far down.

For the same pedal pressure, it is putting the same pressure on the fluid in the master cylinder. Because the cross-sectional area is bigger, the pressure is distributed over more fluid resulting in lower fluid pressure per square inch.

[sourpwr]

I have not spent much time in the jeep since replacing the master. However, the peddle does not go all the way to the floor. It might take a little more pressure on the peddle to stop, but not enough that I really notice it. The Jeep has one of the softest peddle of all of the vehicles that I drive.

-- mike

[pacman77]

the size of caliper or master cylinder bore should not effect the brakes performance it the pressure in the system thats important as long as there in no air in the system or leaks the brakes will function safely.

[CJ7Taz]

Originally Posted by pacman77

the size of caliper or master cylinder bore should not effect the brakes performance it the pressure in the system thats important as long as there in no air in the system or leaks the brakes will function safely.

You need to study up on hydraulics. It’s the pressure that has nothing to do with it. 10psi is enough if the slave is large enough. 100,000psi is not enough if the slave is too small.

The ratio in size of the master to the slave, the length of the pedal arm, the effective diameter of the contact area, brake type, and tire size are some of the most important factors.