Brake Bleeding

[TeamRush]

No problem, pretty common mistake...
I ran into that a lot with motorcycles and cars people were racing... Everyone believes that Master Cylinder BORE will increase breaking pressures...
And it WILL NOT!

Smaller bore to raise pressures,
Longer bore/stroke to produce more volume with same pedal pressure.
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For discs, they use a LOT LESS fluid to apply than wheel cylinders/shoes do...

It make take more fluid to fill the caliper piston up, but once pads are in contact with the rotor, it takes VERY little displacement to apply the disc brakes...
Compared to the volume it takes to apply Drum brakes...

With wheel cylinders, there are smaller pistons, but there are TWO EACH in the wheel cylinder,
And they have MUCH farther to move than...

Disc brake pads do.
When disc brake pads release, the pads only move back as far as off gassing of the rotor/pads force them back,
Generally, around 0.030" from the rotor,
So the caliper piston only has to apply about 0.060" of an inch to apply full breaking pressure.

With wheel cylinders,
The shoes/pistons are retracted from the drums by springs, which compress the pistons back about 1/2" each side...
Even more if the adjuster isn't working correctly and kept snugged up like it should be...
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Remember,
When you are bleeding,
'Foam' is the hardest to bleed!

Moisture causes/creates bubbles, and pressure causes the bubbles to break up into 'Foam'...

FOAM will NOT progress one direction like bubbles will!
Foam is VERY good at taking the compression, then expanding when the compression is off,
(Take a look at what your couch cushions do every time you sit down or get up! Exactly the same thing in the brake lines when they 'Foam' up!)

SO!
It stays in place VERY well, especially in proportioning valves and such...
VERY difficult to blow foam out of anti-lock brake solenoids and and the bottoms of master cylinders, along with the aforementioned proportioning valve!

If you leave foam a day or two, surface tension will pop the smaller bubbles and then you can 'BURP' one large air bubble instead of just compressing/expanding foam!

Bleed until you get CLEAN FLUID!
If you don't, you may leave moisture, air, rust, ect. in the lines!
VERY bad thing to do!
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As for bleeding,
You need someone that will open up their mouth and sing out when they complete the task at hand!

You OPEN the bleeder,
Holler "DOWN",

The helper should depress the pedal to the floor in one smooth, even stroke.
When the pedal hits the floor, your helper should hold it there and holler back "DOWN".

When you hear "DOWN" you should close the valve,
and then Holler "UP".

When the pedal is fully "UP",
The helper should holler "UP"...

Repeat as many times as necessary to get a clean, even fluid flow out of the bleeders.

I've never heard of anyone using a 'Wood Block' under the pedal before, since in most vehicles, 'Half Way Down' has just started to compress the master cylinder piston,
And you are NEVER going to blow the air out of the master cylinder (or any where else) by short stroking the pedal...

[IN2DEEP]

Originally Posted by pontiac58

I dont understand what adujusting the rod has to do with the master leaking out the cap. Mine leaks because the top of the master was never ground smooth just part way

I "think" that the short rod was keeping me from getting ALL the air out of my system. Since I adjusted the rod my master cylinder has been dry......

[sourpwr]

Thought that I would post a quick update...

I ended up having to replace my 30 month old $200 Napa battery. This is the second 84 month battery that lasted 30 months for me. I would not recommend this battery to anyone.

So, Heather helped me to do a final bleed on the brakes. The peddle feels like it did before the wheeling trip, but not as good as I would like.

Eventually, I'll have to replace the master with one that moves more volume.

For those looking for a good reference site check out this site. They do a good job of explaining how the parts work together and the impact of changes.

Master Power Brakes - Welcome

Thanks for the help, cross your fingers that they hold.

-- mike

[CJ7Taz]

Originally Posted by sourpwr

For the record, I'm currently running a stock power brake booster and master with 3/4 ton chevy brakes up front and Caddy Eldorado's in the rear.

Are those Eldorado rear calipers standing straight up and down? An imaginary line through the bolt holes must be vertical. Otherwise, the bleed hole is not at the top of the cylinder and the trapped air above the bleed hole will never bleed out.

[sourpwr]

Correct. I did my final bleeding with the caliper off of the truck with the piston clamped, and the bleeder in a vertical position. I can not tell you how many times I took the calipers off of the truck and put them back on over the course of this bleeding fiasco.

-- mike

[CJ7Taz]

You don’t have to tell me, I’ve got the same calipers on Streetrod Manufacturing brackets at a 45 degree angle.

Have you gotten the e-brake to work adequately?

[sourpwr]

I really have not driven the Jeep enough with the Caddy brakes to have a well informed opinion on their abilities. However, thus far, they have partially performed. They will hold the Jeep in the driveway, but if I shake the Jeep it will creep. Therefore, I always chock the wheels or park in gear.

The biggest problem that I have had with the rear brakes, other than this fiasco, is that the drivers rear outer pad wore 80% through and the inner was hardly touched (5% worn). None of the other 3 sets of pads have worn unevenly, or as much. I see two things happening --the bracket flexes and twists when the brakes are applied and it looks like the caliper was not moving freely on the pins. I intend to stiffen the bracket and will just have to keep an eye on the pads to see if I get the same wear on the new pads.

For the record, the Jeep had been driven about 50 or 60 hours since installing the calipers. Most of that was offroad.

What has your experience been with the Caddy's? Any advice or words of wisdom?

-- mike

[CJ7Taz]

Originally Posted by sourpwr

I see two things happening --the bracket flexes and twists when the brakes are applied ...

That would indicate the brackets are not parallel to the rotors. Are they bolt on or weld on brackets?

The only other advice I can think of is to take the springs off the ends of the Jeep e-brake cables. The calipers already have a spring on the e-brake arm.

[TeamRush]

Originally Posted by sourpwr

I really have not driven the Jeep enough with the Caddy brakes to have a well informed opinion on their abilities. However, thus far, they have partially performed. They will hold the Jeep in the driveway, but if I shake the Jeep it will creep. Therefore, I always chock the wheels or park in gear.

The biggest problem that I have had with the rear brakes, other than this fiasco, is that the drivers rear outer pad wore 80% through and the inner was hardly touched (5% worn). None of the other 3 sets of pads have worn unevenly, or as much. I see two things happening --the bracket flexes and twists when the brakes are applied and it looks like the caliper was not moving freely on the pins. I intend to stiffen the bracket and will just have to keep an eye on the pads to see if I get the same wear on the new pads.

For the record, the Jeep had been driven about 50 or 60 hours since installing the calipers. Most of that was offroad.

What has your experience been with the Caddy's? Any advice or words of wisdom?

-- mike

I swiped the brakes off an '89 Full Size 4 door Cad that was wrecked...
Rears only, and they worked quite well...
AFTER I got the emergency brake pulled about 300 times to take up the slack in the 'Parking' brake side of things!
Didn't hold worth a darn until the thing adjusted up.

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!

What you are describing on the worn pads that caliper might not be moving on the pins...
Probably the piston not letting off like it's supposed to when you release...
Something is probably holding the piston OUT when it should retract slightly....
Usually with REAR brakes that have PARKING/EMERGENCY BRAKES,
This is the piston sticking....

New caliper should come with new pins (good remans do), and don't forget to goop them with 'Never-Seize' before you install the caliper on the pins/brackets!

[CJ7Taz]

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!

You using rotors stamped out of 14 ga sheet metal?

Mine don’t have much slack when I install the calipers with new pads and the pucks turned all the way back in the bores.

If I could turn them out, I would have to go one full turn. There is a short peg on the back of the inside pad that only fits one place into a hole in the puck.

The thread pitch is pretty steep, so one full turn would bring the puck in quite a bit.

More TR BS.

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?