The Stovebolt Site Forums The Shop Area Driveline Brake issues with CPP front disk kit...

So, initial bleed of brakes and test drive did not go so well. Spongy pedal that requires pumping to keep pressure up and brakes somewhat working. Multiple conventional bleeds does not expel any air or improve pedal. Did the following:

Adjusted rear drums a bit tighter, helped.
Checked pushrod. ok...all the way out.
Clamped/pinched all rubber hoses closed and pedal went hard...this is good.
Removed rear brake clamp, pedal stayed firm with a bit more travel. Good.
Released one front side clamp, pedal got soft. Not good
Released second front side, pedal got softer still. Not good

Bleed again, no joy. So, I was thinking air trapped in hard line bends that are above fluid level. But, clamping rubber lines says this is not the issue. Front calipers move/flex slightly upon applying brakes...could be a contributor.

Now I am thinking I need residual valves for front calipers to prevent fluid drain back to lower master cylinder. What do you think? Anything else I should do or check?

Going to call CPP on Monday.

Find out if fronts or rears are holding/actually braking. See if one is not. Residual valves needed for shoes, usually not for pads. If you told CPP you had rear drum and front disc, they would have sent the correct parts to you or advised what you needed. Proportioning valve, residual valves, bleeding instructions, etc. Never had a problem with installing front disc from CPP. Spongy=air=leak, need to vacuum bleed or wrong components.

Thanks for the response. I bench bleed master. All wheels actually do hold and I can drive the truck and stop, just not confidently or with authority. Pedal to floor unless I pump them, then more stopping power. I did purchase rear drum, front disk kit. Another possibility is pads retract too far and not enough pushrods stroke to compensate. I do get caliper mounting plate flex which concerns me.

If your brackets, callipers and rotors are from CPP, should be no flex. Pads only relax not retract. If you can pump up the brakes, that does usually mean air in system. Be sure to examine, with a good light, all areas of truck for leaks. The leak does not always drip to floor or is not easy to find. A fluid leak is also an air-in leak. Could be at any fitting joint/hose joint/banjo. What exactly is flexing and what direction? What truck is this? Good that you bench bled MC. After no leaks found, Bleed and bleed again. Some bleed methods don't work so good by yourself. The residual valves are necessary because the shoes do retract allot because of the big springs. They get too far away from drum and the Res Valve keeps the pressure "on" them. Be sure you have those in the correct port(s). If residual valves are present and in correct place, I say it's air in system or leak and needs more bleeding. You are pumping up the fluid AND the air to get stopped and when no pedal pressure, system looses fluid volume sort of. If you don't pump, does it go to floor or just near floor. Like you said you did, recheck the shoe adjustment again also, drum should stop turning then back off til starts to move....barely.

Did you get the master cylinder with the kit?

Yes. Front disks, master/booster/proportioning valve kit all from CPP.

Rear brakes don't seem to be the issue because if I clamp the front rubber hoses closed, then the pedal is firm and almost immediate...like I would expect. Shoes are adjusted so slight drag is felt and then adjusted backed off 3 clicks.

I did have a small leak at one front caliper line splice block. But, with hose clamped closed, this did not make a difference and pedal remained firm. This tells me problem is at caliper.

Sure sounds like air in the system

I don't think lack of residual valves is an issue
I'm not using them on my system and have great pedal pressure
I'm using a manual master cylinder.

It does indeed "feel" like air in the system. But, no amount of conventional bleeding expels any additional air. Bleeder nipples are at the high point of caliper. Dang this is frustrating.

You might want to consider getting a motive products power bleeder. They are not real expensive and I have had great luck using it. It also makes bleeding the brakes a one man job.
Are the brake drums new? How far are the brake pads retracting from the rotor after you press the brakes? That is the reason for using a residual valve, it keeps the pads close to rotor without dragging. The master cylinder doesn't have enough volume to fully push the pads against the rotor with one pump if they are to far away.

Mine feel the same w/a manual CPP disc kit and no air, no leaks. The pedal initially feels too soft compared to what I am used to in modern power braking. However, I am able to lock em all up if I push the pedal firmly and in casual stopping if I pump it once pressure builds and I don't feel like I might need to stand on it while waiting for the light to change. This happened with the CPP and POL Corvette MC as well as the CPP Mustang type MC I am currently using. I don't know how much of this is simply because they are manual brakes (my buddy's '52 F1 feels the same with a similar manual kit) but have noticed a significant amount of flex in the CPP/POL MC bracket which may be causing some of the issue. I was considering adding an additional gusset to the bracket as well as switching to steel braided soft lines to see if that helped.


The residual valves actually keep the MC from siphoning the fluid from your calipers/cylinders when your MC is located under the floor. If your MC is in the stock location, you should be using a 10lb valve on the rear and a 2lb valve on the front. This is important when the truck is lowered, in my case, the MC is below the calipers but even at stock height it can happen on an incline.

that small leak you found may be introducing air into the system?

I while back I remember reading a post where a guy had a bad new M/C out the box

bad new M/C out the box = BOOB (Bad Out of Box).

Anyway, I called CPP. Their initial response was that I did not bleed the MC properly. I left the master cylinder connected to the power booster and was told that is wrong because I do not get full stroke and end result could be air left in MC. I find this hard to believe since clamping hoses results in hard pedal. But, I will remove MC and bench bleed again. Then when that does not work, go from there.

Spongy is one thing, but if pedal goes to floor, that's a big problem. You need to read CPP instructions again. It specifically states that you must remove all components from MC. Use short long strokes and tells what to plug off and where to attach enclosed bleeding kit and to make sure MC is off the truck and level. I think that is your problem. The first step in your "pinch hose" test is to plug the MC and test, if that gives hard pedal, proceed to release one clamp at a time until spongy. That is supposed to identify the circuit that is faulty. I think all that is a bad idea. If MC is bled and each wheel is bled and no leaks, it will not be spongy with good parts, correct fluid and proper valves. New wheel cylinders in rear? As last resort, check under the wheel cylinder boots for small leaks.

All brake components are new. spongy pedal is due to calipers. Like I said before, with hoses pinched closed, the pedal is immediate and hard/firm. Release rear hose and pedal remains firm, but less immediate. Release one front caliper at a time and I start to loose the pedal. How can this be a MC bleed problem. To me, if I have air in MC, I would get spongy pedal with hoses clamped off. Does not compute.

But, I will do what CPP suggests to make sure. I am anticipating nothing will change. But, if it fixes the problem, I will be sure to admit fault.

I don't know or trust your hose method. I would have to experiment more. Like: reverse your statement and release front first and then try releasing one at a time and like I said, plug the MC off first and all that.. I don't think you are proving anything except you have air in the system. The callipers relax, they don't really retract, they are always almost in contact. Proper bleeding will fix it. You already bypassed an important part of install....you are guilty
Go to the instructions and follow exactly. I read them on the CPP website.
I understand your logic about it all and how could MC air cause it. I don't know, but a theory could be that the spongy is at the plunger stroke and that the air "bubble" stays in the MC or in a "chamber" for only the fronts or rears. I don't know how air manifests itself in a system. If you see a bunch of bubbles when bench bleeding, you will be happy.

http://www.classicperform.com/TechBook/BrakeBleed.htm
Scroll down to MC section.

Thanks Bart. Yes, I read that instruction set you linked to long ago. I bench bleed all air out of MC will the assembly still connected to the booster. So, yes it is possible that short plunger strokes did not get ALL the air out.

By pinching the rubber hoses (one at each caliper and one at rear axle) closed, I effectively take the calipers and wheel cylinders out of the equation. With the hoses pinched closed, fluid cannot move, past the pinch, to the caliper or wheel cylinder. So, any air in the calipers or wheel cylinders is taken out of the equation. Now, the fluid has no where to go, so the immediate and hard pedal is surely expected. But, to me, if there is compressible air in the MC or anyway in the hard lines between MC and pinched part of rubber hose, then I should expect to get a spongy pedal as the air is compressed. No spongy pedal, no air. This is why I doubt I have air in the MC.

I will do as you suggest and release front first. This might tell me something about the proportioning valve not behaving properly.

Update: Well, it seems CPP was right and I had air in the MC. Removing the MC and bench bleeding, sans booster, did expel more air. Took me awhile as my installation prevents removal of the MC without first removing the transmission cross member. I have a brake line routed on the rear side of the cross member. But, luckily, the line starts at the proportioning valve on one side of the cross member and ends at a splice block on the other side. Like I planned it that way...hmmm maybe or maybe not as I can't remember. I still have not bleed the brakes as my helper was MIA, and tonight we are all too busy.

I think you are getting somewhere now David. Good job! Lets hope all goes well.

Update:

Bled brakes last night and no joy...still have soft pedal to floor. This after removing MC from booster and bench bleeding again. Suggestions?

You have spoken about the proportioning valve several times, you have mentioned residual valves once saying "maybe I need them in front". Do you have them and where are they in the system? They are typically mounted right on the prop valve, a 10 lb for rear and 2 lb for front as has been said. You may only have one for rear. Be sure it's there in the correct port ,before the split, and is not backwards. It may have come pre mounted. You should have one front line with a split to left and right and one rear line with split to left and right. Is that what you have?
Ok David, you have three possibilities, not correct/missing parts, bad parts or you have it plumbed wrong. My suggestion: Instead of having everyone ask you "did you do this or did you do that" etc. (like I'm starting to do)
Why don't you tell us exactly how it's plumbed from MC on out. Explaining every fitting, valve and how lines are split...every detail. In doing this you may see the problem yourself or someone may catch it. I know it's a simple system and you know what you are doing but we have to start this way. We have all stared right at a problem and not seen it for days. Also include what is NOT new at front brakes and what is NOT new at rear brakes. Take off rear drums and inspect each rear brake assembly to see all parts present and installed correctly. Compare to a picture from a book or the web. Visually observe the front brake operation. Keep an open mind. Do not assume anything is correct. Look at it as if you are somebody else. Something bigish is wrong. If all pans out, maybe you have a bad part. If you decide to post the info, look at the whole system again before posting, don't guess it's right. This is the quickest way to get help from afar without a bunch of back and forth. You don't need the hose squeeze test anymore. It is not identifying anything. Can you see the fluid level in MC? or is it blind? Please examine every inch of the system for a fluid leak with a good light.

David, all good info has been posted but I'll add my experience.

I went through similar problems getting my stock Hucks setup after a full 100% brake system rebuild.
My pedal was spongy and I'd have to pump the pedal to get a good hard brake pedal.
My problem ended up being that I had several very small leaks.
They didn't leak much but I figure the leaking would suck air back into the system when pressure was relieved which added to the problem.
I had 2 3-way blocks that leaked and one fitting one a rear wheel cylinder. After I found and retightened those joints I've had no further brakeing problems.
How i found them was to have a helper working the brakes while I was under the truck inspecting each and every junction.
Good luck
Dave

Thanks guys. Leaks have been identified, corrected and fittings are dry. I spoke with both CPP (supplied MC, booster, and prop valve) and Brothers (supplied disk brake conversion kit). CPP agreed that the clamped hose test means no air in system from pinched hose to MC (due to hard pedal with all four brakes pinched off). Was not too worried about possibility of air in short line that goes up above MC fluid level and back down to prop valve. Suggested I bleed at prop valve fitting just to be sure. CPP wants me to adjust rear shoes tighter. Basically adjust so wheel will not make 1/2 rev by hand. Then leave it that way without backing off adjuster. CPP is concerned about flex in front caliper and mounting bracket. I will inspect to ensure pads are contacting disk square. Talked to Brothers about this as well and they want me to inspect caliper casting and pin to ensure caliper is moving on pin properly. CPP also wants me to remove caliper for bleeding and insure bleed valve is perfectly at 12:00 position...its more like at the 12:30 position while mounted.

Here is how system is plumbed:

Front (actuator rod end) MC reservoir/port is plumbed to rear inlet port on prop valve. Rear MC reservoir/port is plumbing to front inlet port on prop valve. front outlet ports on prop valve plumbed to calipers (one for each, no shared line). Rear outlet port on prop valve plumbing to rear "T" on axle. "T" plumbed to each rear wheel cylinder. There are no residual valves installed in the system. Both CPP and Brothers said not absolutely necessary and will only result in more immediate pedal, but will not fix spongy pedal. All hard lines are 3/16".

So, my plan of action. Tighten up rear shoes. Pinch all hoses closed and ensure I still have hard pedal. Release rear hose, check for firm pedal. Inspect and correct caliper/disk alignment issues, if any. unclamp one caliper hose at a time and fix pedal feel before unclamping other/last caliper. Fix pedal issues with last caliper.

After that, if I still have issues, I am getting my shotgun out.

I would be worried about the rear drum brakes being adjusted that tight. A very slight drag is what you want. Anything more will create lots of heat and other problems. Or at least that's my thoughts.

Since brake shoes are new, I am thinking a tight setting will be ok as the shoes will wear/fit into the drums and loosen up quickly. I will keep an eye on temperature for sure for the first few miles.

Is that how CPP recommends running the front?
On my POL kit I used one port for the front and a T
A the time I was installing it I found a diagram showing it run that way. But as everything else with these kits, nothing is definitive.


What method are you using to bleed?
2 man? 1 man?

I did mine one man with a brake line submerged in a jar. I could see when there was no air.

I discussed with CPP how the prop valve was plumbed and he said I did it correctly. I have the valve plumbed like this.

2 man bleed method.

One thing I did not mention is that I get good flow out of rear wheel cylinders when I crack open the bleed screw. On the front not so much.

Wish I had Speedy Valves to make it a one man job.

1.Your plumbing drawing says 10 Lb residual, I guess it's there or built in? Also says you can use a "T" in front. Residual is just a big long fitting at the rear port.
2. Nice to buy all at one place!
3. Be careful taking instructions from a supplier that did not supply the parts.
4. 12:00/12:30 sounds like 180 degrees off, Are you saying the bleed is down at the bottom, close to the ground type bottom?
5. The tight shoes will not hurt and are necessary for now to be sure it's not that. Once found, can go back and loosen a little if you want. You are correct, they will conform after a while.
6. The vendors are going to blame the other guy.
7. "Valves won't fix spongy pedal", tightening shoes won't fix spongy pedal, flexing plate won't cause spongy pedal.....air in system will cause spongy pedal, bleeder not high up will cause air, leaks will cause air. Dads is correct, now you have to see if bubbles come out, can't do a leak to ground bleed. Have to have a method that you can see if air is purging and then sucking in again. Because that's what it seems like. It would be odd to be getting air in and no leak. But the fact is spongy is air, unless contamination.

That front bleed screw should be right on top.

My P.O.L. Has it there when bolted in.
....pic....


If its not dead 12:00 when bleeding it can creat an air pocket in the caliper piston.

One good thing about the one man kit is that you run a clear hose from the bleed screw and run it to the accumulation jar that is sitting at a low position.

You can tell when all the air is out just by looking at the clear hose




Instead of clamping brake hose you can just plug one front port at a time and test, leaving one circuit installed. The plugs should of come with the prop valve.

A bit more work but you might be able to tell if its the front left or front right that's the issue.

My cousin just had a problem with his brakes after we had to take it all apart to install a SBC in it.It turned out to be one of the brake pads,caliper, was hung up on one of the sliders.It all looked good but the bracket was flexing just a little.We took it apart and got it to move free and all is well.It's on a 54 1st with a CCP kit.Same soft pedal as you.We also thought there was air in the sys.



Pete

I wonder if the valve inside the proportioning valve is off center? If you are getting good flow at the rear and not at the front that is an indication that the valve is off center. You should try bleeding the line for the front brakes that goes into the proportioning valve, see if you have good flow going in to it.

Sounds like Pete may have your answer.

It's fixed. Problem was caliper mounting plate not manufactured correctly. Basically, the front brake pads were not parallel to the brake disk. So, it took too much pedal travel to force the pads to the disk. Contact was on edge of pad only. Both front calipers had this problem. Using a large crescent wrench i bent the bracket to allow proper alignment. Careful measurement to ensure top and bottom mount were same distance from rotor and parallel. Pads now make even contact and pedal does not go to floor and performance is good. All visual flexing/movement of caliper when brakes applied is gone.

To be clear, CPP was the MC cylinder/booster manufacturer. Brothers was the disk brake kit manufacturer. Neither blamed the other and were generally eager to help solve the problem.

The caliper bleeders are virtually straight up if not at 12 high, just a bit off vertical like if the hour hand was at 12:30 or less. It did not matter. With caliper removed and pads blocked in place, I could get no additional air out of system.

I do not have any residual valves added. It is my understanding that proportioning/balancing valve has 10 psi residual valve built into the rear outlet port.

Thanks much to all who offered suggestions. They all got me thinking.

Glad to hear you got it fixed. Thanks for letting us know what you did to fix it. Don