Major brake issues, help please

[Mike (Asheville)]

Originally Posted by RichardJ

>>from Chris_oz
Is the master cylinder returning all the way back? <<

>>from 88Stanger
I have checked the distance the rod is extending from the booster when the brakes are depressed fully.<<

I tried to reread all the posts and I'm not sure how the booster pin length was checked. The retracted pin length is what is important and must be checked.
Loosen the MC and space it away from the Booster with a couple of thick washers or anything that will temporarily separate them. Try bleeding again.

Almost certain to be this ^^^^.

Remove the nuts that secure the master cylinder to the booster. Then slowly push the master cylinder along the mounting studs until it's seated properly in the booster. If you feel any pressure at all the pushrod is either too long or not fully seated within the booster.

[88Stanger]

Mike,
I did check that depth. I used depth gauges and a micrometer, I also used the putty idea and it checks out to spec that wilwood requires.
Really appreciate the idea though.

[Mike (Asheville)]

Originally Posted by 88Stanger

Mike,
I did check that depth. I used depth gauges and a micrometer, I also used the putty idea and it checks out to spec that wilwood requires.
Really appreciate the idea though.

I appreciate what you're saying but having done it several times I've found it almost impossible to "measure" the length since the master cylinder recesses into the booster by about a half an inch. Feel is a more reliable indicator. This may be one of the only times where "you can be too short but can't be too long."

[AussieinNC]

This might be a silly question...but have you screwed down the knob on the proportioning valve prior to bleeding the rears?

Rotate the knob clockwise at least ten turns, then try bleeding the system again...

Also, I assume you are using the old "have a buddy press the pedal down then crack open a bleeder" technique? I stopped doing that a while back...I now use a power bleeder with a plate attachment that covers both master cylinder reservoirs....pump it up with a full load of fluid, then starting at rear open each bleeder until a full stream of fluid comes out.

Makes bleeding a one man process...

If this gets your brakes functional, back off the proportioning valve knob conterclockwise 8 turns...then give it a little test drive....

To increase rear brake pressure turn the knob clockwise until the rears lock up a little too easy, then back it out one turn at a times until it feels good for your driving style.

[88Stanger]

Originally Posted by Mike (Asheville)

I appreciate what you're saying but having done it several times I've found it almost impossible to "measure" the length since the master cylinder recesses into the booster by about a half an inch. Feel is a more reliable indicator. This may be one of the only times where "you can be too short but can't be too long."

Mike, I went and tried your idea. After putting in couple washers the space at the pedal before you feel it against something is now further down then before.
I understand your concern about the pin being recessed into the booster. I took a machinist flat ruler and laid it against the booster wall, then took a depth measurement to head of pin from a the flat surface of the booster, then did the opposite (sort of) to the MC. Did a little math and have 1/8th inch gap. Then I tested this with the clay on the booster pin and attached the MC fully, it too showed about 1/8" gap.
With your idea of the washers doing what it did makes me think it is ok. What you think? What I'm feeling at the pedal what it should be if it is done correctly?

[88Stanger]

Originally Posted by AussieinNC

This might be a silly question...but have you screwed down the knob on the proportioning valve prior to bleeding the rears?

Rotate the knob clockwise at least ten turns, then try bleeding the system again...

Also, I assume you are using the old "have a buddy press the pedal down then crack open a bleeder" technique? I stopped doing that a while back...I now use a power bleeder with a plate attachment that covers both master cylinder reservoirs....pump it up with a full load of fluid, then starting at rear open each bleeder until a full stream of fluid comes out.

Makes bleeding a one man process...

If this gets your brakes functional, back off the proportioning valve knob conterclockwise 8 turns...then give it a little test drive....

To increase rear brake pressure turn the knob clockwise until the rears lock up a little too easy, then back it out one turn at a times until it feels good for your driving style.

May I ask where you got the power bleeder and the MC lids?
I have the adj. Prop valve all the way open. I know this is open because i used a pressure gauge 1st on the MC, each port, then on the prop. Valve and both had same # of about 1000lbs without vacuum ti the booster.

[dbm52]

with 1000 to 1500 psi at the rear brakes you should have plenty of brake. is it possible you have mounted the calipers upside down, ie the left caliper on the right side & the right caliper on the left side this would put the bleeders on the bottom. the bleeders must be at the top of the caliper

[88Stanger]

Originally Posted by dbm52

with 1000 to 1500 psi at the rear brakes you should have plenty of brake. is it possible you have mounted the calipers upside down, ie the left caliper on the right side & the right caliper on the left side this would put the bleeders on the bottom. the bleeders must be at the top of the caliper

Blenders on bottom. Checked many times. Lol

[HO455]

What parts have you not changed since you started? I couldn't see where you changed the rear hose since you started the thread. You said it was new and you inspected it, but have you done your pressure test at both ends of the hose? Yours wouldn't be the first new part to be defective. I have seen hoses that work when straight or at low pressure, but kink up internally under pressure or bending.
Good troubleshooting isolates the problem area. Define the problem. Verify the source as pass or fail. Then spilt the system in half and verify pass or fail. Keep dividing the system until you have isolated the failure point. Don't assume any part is good until you test it under load.
So you have good pressure at the caliper. FALSE
You have good pressure at the master cylinder. TRUE
You have good pressure at the outlet from the proportioning valve. TRUE
Next step is go to a convenient pressure test point between the proportioning valve and the caliper. Like the hose connection to the hard line at the frame. Or at the axle end of the hose. Or at the double male connection under the passenger seat floorboard.
Good luck.

[71threequarterton]

Originally Posted by 88Stanger

May I ask where you got the power bleeder and the MC lids?
I have the adj. Prop valve all the way open. I know this is open because i used a pressure gauge 1st on the MC, each port, then on the prop. Valve and both had same # of about 1000lbs without vacuum ti the booster.

Check this out, this is the one I just got: https://www.youtube.com/watch?v=2MmKaa3IVMo

There are a lot of different MC lid adapters available and you can buy a kit with the one you need.

[RichardJ]

>>88Stanger #33

Originally Posted by dbm52

with 1000 to 1500 psi at the rear brakes you should have plenty of brake. is it possible you have mounted the calipers upside down, ie the left caliper on the right side & the right caliper on the left side this would put the bleeders on the bottom. the bleeders must be at the top of the caliper

Blenders on bottom. Checked many times. Lol <<


?

[LH Lead-Foot]

No photos of rear caliper yet, but every post is good information. As a retired ASE Master tech, I grew in the age or rebuilding components, not opening boxes.

When it comes to rear disc w/E-brake, the piston screws in for new pads or out for service. Working the lever to advance the piston(s) toward the rotor is required. Yes, it take a long time to get all of the air out the line to both rear calipers, but you indicated 1000 - 1500 lbs. with little fluid. You will not get as much as front in normal conditions, but you have all aftermarket components with a knob on the proportioning valve. You're on your own there with customer service on speed dial.

I don't know what the answer is for your magical mystery tour of 2018's winner of the most expensive/longest brake job... and still no rear brakes.

Your pressure should work and the rears take little volume to move the piston(s).
Pressure bleeder, yes! Buddy pumping the pedal, press twice, then hold. Open blender screw, pedal drops. Repeat until no more bubbles. Easy right?

In short, everything should work! I know as well as anyone, that to go fast, you need to stop very well. But WoW, surrr do look perrrty!

Glad I used all GM parts to get disc brakes on my 1967 C10.

[88Stanger]

Originally Posted by RichardJ

>>88Stanger #33


Blenders on bottom. Checked many times. Lol <<


?

Lol, my bad, they are on top. Sorry about that.

[88Stanger]

Originally Posted by LH Lead-Foot

No photos of rear caliper yet, but every post is good information. As a retired ASE Master tech, I grew in the age or rebuilding components, not opening boxes.

When it comes to rear disc w/E-brake, the piston screws in for new pads or out for service. Working the lever to advance the piston(s) toward the rotor is required. Yes, it take a long time to get all of the air out the line to both rear calipers, but you indicated 1000 - 1500 lbs. with little fluid. You will not get as much as front in normal conditions, but you have all aftermarket components with a knob on the proportioning valve. You're on your own there with customer service on speed dial.

I don't know what the answer is for your magical mystery tour of 2018's winner of the most expensive/longest brake job... and still no rear brakes.

Your pressure should work and the rears take little volume to move the piston(s).
Pressure bleeder, yes! Buddy pumping the pedal, press twice, then hold. Open blender screw, pedal drops. Repeat until no more bubbles. Easy right?

In short, everything should work! I know as well as anyone, that to go fast, you need to stop very well. But WoW, surrr do look perrrty!

Glad I used all GM parts to get disc brakes on my 1967 C10.

Thanks for the response. I started out this journey with just a front disc conversion. All seemed good, then I decided to go to a rear disc conversion using all GM equipement, rear calipers are from 1980-1985 Cadillac Seville, rotors are from 1990s GM truck, all 6 bolt pattern. I bought a disc/disc prop. Valve and got no rear brakes. Worked and worked on them, bleeding for hours, still no brakes. Replaced all hard lines, checked for leaks, still to pressure at rear brakes. Front worked great. In this time, I found the rims I wanted, but they came only in 5 lug, so I changed out to 5 lug. Not hard really, not to expensive, but still no brakes. After all this and so frustrated I contacted WilWood. They emailed me quickly and we emailed a couple times. In this time I decided to just go all out and get Wilwood system front and rear. It is their lowest set, but nice stuff. I have not tried them yet because I need to order new flexible lines at each caliper due to different banjo size, BUT the calipers take standard GM brake shoes, D52 and D154. So this weekend I'll install the new lines and give them a shot.
After all this, not sure who was the first to mention it, but I believe the issue wuth the original GM stuff is as you said adjusting the rear caliper piston, of which I did not do, nor did the instructions I got did not mention doing this and I have never really worked with this type of caliper before.
Oh well, the new Wilwoods look nice and are rebuild able. Not that this justifies getting the Wilwoods, but I like them.
I'll post how the new Wilwoods work. Lol now I'll have a full rear conversion to sell. Lol