Major brake issues, help please
 

I have been fighting a brake issue for far to long. I have little to no pressure at the rear, here is what i have and here is what i have tried:

1969 C10 complete rebuild from ground up with LS conversion
all new brake lines installed, front to rear
Disc conversion on Front and Rear
new POL Wilwood power booster, dual master cylinder and Disc to Disc prop valve

I am trying to bleed the brakes and the rear bleeders have only a small amount of fluid coming out, with little to no pressure. This is after an hour of bleeding the brakes the good ole way with buddy on the brakes and me bleeding.
The master cylinder does have the plug installed where the warning light goes
no leaks to date

i have checked the distance the rod is extending from the booster when the brakes are depressed fully. there is full travel on the brake pedal also

i did pre-bleed the master cylinder also with a bleeder kit

So thats where i am. I am just frustrated. i have searched and tried what i know of so far other than connecting the rear line directly to the master cylinder and seeing what pressure i have then. i do have an adjustable prop. valve from SSBC valve that i also plan to try after the direct connection.
I am open to any and all ideas at this point.
Thanks in advance for any help.

Re: Major brake issues, help please
 

If it were mine, I would disconnect the brake line going to the junction at the back and see if fluid comes out strong when your buddy presses on the pedal. If you're getting fluid there, keep working your way toward the rear brakes and see how the flow is at the brake line going into the rear caliper.

It may not be the fix, but it will give you information to help diagnose the problem.

Re: Major brake issues, help please
 

Did you change the pedal ratio?
Does your prop valve have a reset button in the front like this one (black cap)?
https://leedbrakes.com/i-19296666-pr...isc-brass.html

Re: Major brake issues, help please
 

2X this. You may have a bad hose at the axle. I would start at the top of the hose. Then you have divided the system in half. Depending on whether you have pressure or not decides which direction you go next. Either way Saxart is spot on. Trace back to see where the first place pressure is present.
In my world the hose is more likely to be defective from the factory than the rest of your new components. That being said I have had several new master cylinders not work out of the box. Mostly due to debris in the bore preventing the seals from trapping fluid to make pressure.

Good luck

Re: Major brake issues, help please
 

x3 for a collapsed or degraded rear axle hose (just a guess though!)

Re: Major brake issues, help please
 

I thank each of you for the responses!! I really appreciate it. So frustrating.

So with anticipation of this, I ordered a brake pressure kit. I completely agree with find where the pressure is first, then find where it is not and addressed it then.

Re: Major brake issues, help please
 

great advise

Re: Major brake issues, help please
 

All good suggestions from others...lots of very knowledgeable folk here....

I suspect the proportioning valve has sensed the bleed process, tripped over and blocked off the rear brake circuit...

Did you use the tool to stop the prop valve from tripping over? Like

https://www.classicindustries.com/pr...2.html#reviews

If the rear hard line before the flex hose has little to no pressure, the prop valve has tripped over...

Remove all switches from the prop valve and master cylinder and jump on the brake pedal once real hard...the trip valve will usually reset itself.

Also, try bleeding the system using a pressure bleed canister tool with and adapter to fit the top of the master cyl...

Constantly pushing the pedal only aerates the fluid and causes more issues.

Finally...hope you are not using DOT 5 fluid...its is silicon based and not suited to most aftermarket systems...stick with DOT 3 or DOT 4....

:chevy::chevy::chevy:

Re: Major brake issues, help please
 

Ok, well i decided to order all new hard brake lines from classic industries, pre-bent for my truck.
Got them in and went ahead and installed them. Damn, its nice to use stuff already pre-bent.
So now here is what i have:
from POL i ordered their Power booster, Wilwood 1" piston master cylinder and disc to disc prop valve. I bench bled the Willwood master and got all the air out of it. Then installed the brake bleed tool into the prop valve (Like the one AussieinNC posted). I did need to remove the piston and re-install it to a position that is correct and allow the tool to be installed correctly, into the v notch as it should.
Then i installed all the brake lines from front to rear, front and rear systems including across the rear axle. The only items left not changed out is the rubber hose from the frame to the axle, which is brand new, but i checked it out and it appears to be working fine, not blocked.
After all this, i vacuum bled as much as i could, then had a buddy over and do the you push the brake, hold it and i open the bleeder. We did this and still at the rear, little to no pressure and the pedal does not go all the way to the floor, like the fronts do.
Now im really frustrated!!
So, i started the pressure test from the rear towards the front. I still was not getting the pressure i should, so i worked my way forward, still nothing.
So, what to do now. I took off the master cylinder with the prop valve attached and thought, i want to do a test, basically a pressure/bleed attempt with the prop valve attached, and dang, lots of air came out, so i kept bleeding it until all the air was done.

Could the air in the prop valve cause the issue?

This weekend im going to re-install the master and prop valve after i bled them both and give it a try.

Re: Major brake issues, help please
 

Is the master cylinder returning all the way back? I have seen it many times the pushrod is too long, not allowing the piston to return all the way, it can stop the flow of fluid into the body of master cylinder bore.
Bench bleeding it and all is good, on the car no flow.
Check that you have free play when the pedal is at rest.

Re: Major brake issues, help please
 

Chris_oz
I measured the distance your asking about and used some clay to check distance and it's all checking out.
Out of just raw frustration I order the adjustable Wilwood prop valve and bracket that goes together.
Thanks for the thought, any others?

Re: Major brake issues, help please
 

Yes absolutely yes

Re: Major brake issues, help please
 

Ok, got new Wilwood adjustable prop valve. Bled the master cylinder, then attached the prop valve and bled it. I then attached the master to the brake booster, then blocked off the front port on the master cylinder and added a pressure gauge to the rear port. Pressed brakes and get a reading of about 1000lbs, reversed this and got the same. Then i for giggles, i started the truck (LSMotor) and get about 12" of vacuum at idle without it being tuned. Then i hit the brakes and get about 1500lbs of pressure on each, it did help to rev the motor a bit to get the vacuum up a bit, again just for giggles.
So now i installed all new brakes lines, front and rear. Checked for any leaks, none.
Now, i go to the passenger side rear to do the brake bleed, having buddy to the pumping of the brakes, i turn the brake bleeders and some fluid comes out, not alot, but some and not under much pressure, but he gets nothing at the pedal. This is different than the fronts. If i do the front brakes, the pedal moves towards the floor as i turn the bleeder screw and bleed the front brakes, but this does not happen to the rear. We continue to bleed the rear and still nothing, no pressure at brakes shoes. I unscrewed the banjo fitting from the left side and asked my buddy to press the brakes pedal and tell me if he feels the pedal move, he said he did a bit.
Bascially, if i smash the rear brakes to the floor, i an still rotate the rear wheels if in neutral.
Any other ideas? Damn i just want to drive the damn thing!!!!

Re: Major brake issues, help please
 

If you have fluid coming out of the hoses at the rear calipers when they are disconnected but none or very little coming out of the rear caliper bleed screw I think there is a problem with the rear calipers. Manufacturing defect?? I'd take them apart and verify all is good with the fluid path.

Re: Major brake issues, help please
 

Have you adjusted the rear calipers so that the pads are almost touching the rotors? If you try to bleed them without the resistance of the pad to rotors, you could just be cycling the pistons in the calipers. I'm not intimately familiar with rear discs, but I've seen where not being properly adjusted was an issue. The fronts don't use a parking brake for the take-up due to wear, like the rears do.

Re: Major brake issues, help please
 

Steevee, I did not, but out of just dire want, i just ordered the Wilwood rear conversion and front disc brakes. Always wanted them, so now is a good time to "justify" it to myself. Lol

Re: Major brake issues, help please
 

The emergency brakes have to be adjusted up on rear disc brakes. You will get weak fluid flow and you will be able to turn rear brakes with pedal pushed. Don't ask me how I know this 3 day disaster. I can't tell you what to do but I can tell you what not to do!

Re: Major brake issues, help please
 

I can't speak for the Wilwood brakes but the CPP rear disc brakes suck! I hate I ever spent the money on them. I never have gotten them to work as good as my old drums did. I have spent weeks on them adjusting them and bleeding them. They are the worst upgrade I ever done.:chevy:

Re: Major brake issues, help please
 

Well that unfortunately sounds like it could be the issue, as we have done everything else. But, I did buy all new 2 piston wildwood for rear and front. That way I'm all Wilwood.
Thanks for all the input. Maybe it will help others

Re: Major brake issues, help please
 

Which Wilwood adjustable prop valve and how did you plumb it? Would really like to see a clear picture of the plumbing.

Re: Major brake issues, help please
 

This is another great point , the majority of aftermarket brake systems have this issue , and it is hard to diagnose , kicked my butt for a year on a chevelle

Re: Major brake issues, help please
 

I bought stock replacement lines from classic industries. The master and adjustabke prop valve and booster are the all black kit offered by POL. They plumb together with supplied lines. Then I installed the stock lines for a 1969 short fleet side. My 2" drop spindles and such came from CPP.

Re: Major brake issues, help please
 

That's a clean looking proportioning valve. I like it! :metal:

Re: Major brake issues, help please
 

Thank you sir. Been a long ride, but almost done. Fully rebuilt LS motor is just waiting to go to tuner, but need brakes 1st. Lol these just showed up for the front replacements, rear shows up today.

Re: Major brake issues, help please
 

>>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.

Re: Major brake issues, help please
 

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.

Re: Major brake issues, help please
 

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.

Re: Major brake issues, help please
 

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." :lol:

Re: Major brake issues, help please
 

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.

:chevy::chevy::chevy:

Re: Major brake issues, help please
 

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?

Re: Major brake issues, help please
 

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.

Re: Major brake issues, help please
 

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

Re: Major brake issues, help please
 

Blenders on bottom. Checked many times. Lol

Re: Major brake issues, help please
 

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.

Re: Major brake issues, help please
 

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.

Re: Major brake issues, help please
 

>>88Stanger #33

Quote:

Originally Posted by dbm52 (Post 8363585) 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 <<


?

Re: Major brake issues, help please
 

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.

Re: Major brake issues, help please
 

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

Re: Major brake issues, help please
 

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