Brake issues driving me bonkers!

[supertrkr]

Hey guys. I'm having trouble with nailing down a brake issue. So here's the skinny.
1968 C-10 with manual brakes
CPP Disc brake conversion rotors calipers and spindles.
CPP 1" bore disc/drum aluminum master with prop valve
Ford 9" out back with drum brakes

So here's the issue and what I've tried. My pedal is garbage. The pedal goes 3/4 of the way down before the brakes start to work. I've bench bled the master 3 different times. I used a power blender to bleed 3 16 oz bottles of brake fluid the the system. I clamped off all the brake lines and the pedal is rock hard. I unclamp the rear line and the pedal goes down about 1/4 inch. I reclamp the rear line and undo the front clamps and the pedal goes back to crap. The rear brakes are adjusted up. I know that's telling me that there is a problem with the front somewhere between the clamp and the caliper. Has anybody experienced this? I spoke with a CPP tech and was told I had a problem that had them stumped. Basically they sold me a longer rod and clevis for the pedal against my better judgement. Any advice would be GREATLY appreciated.

[dmack91]

Just a basic question. Are the bleeder screws on the front calipers at the highest point in their (the caliper's) reservoir? I know some of the calipers can be mounted on either side but it puts the bleeder screw low and allows air in the internal cavity above the bleeder screw.

Good luck with it - you already found the problem it took me 2+ weeks on my 9". I hadn't adjusted up the rear star adjusters. Felt stupid but at least it was a simple fix.

[Blown06]

What dmack said, seen it before where calipers get mixed up or you get the wrong part.

[supertrkr]

Both bleeder are facing up. I don't know the master might be bad or the prop valve or a caliper or two. Driving me crazy! Lol

[supertrkr]

Hey dmack I had one of those moments too. Lol couldnt figure our why the front hoses were leaking. Well they were on upside down. So don't feel bad. Lol

[Blown06]

Bleeders are at the highest point? Not just facing up but take a good look and see that the are at the highest point. Not being a wise butt or anything, tried chasing a similar problem with a friend on a jeep. Bleeders weren't at the highest point, leaving an air cushion in the caliper. Found out we had been given the wrong caliper to begin with.

Sounds like air in the caliper though, that's about the only ideas I can toss out without actually putting my hands on it. I'd be interested to hear what you finally find though, good luck.

[supertrkr]

Originally Posted by Blown06

Bleeders are at the highest point? Not just facing up but take a good look and see that the are at the highest point. Not being a wise butt or anything, tried chasing a similar problem with a friend on a jeep. Bleeders weren't at the highest point, leaving an air cushion in the caliper. Found out we had been given the wrong caliper to begin with.

Sounds like air in the caliper though, that's about the only ideas I can toss out without actually putting my hands on it. I'd be interested to hear what you finally find though, good luck.

I'mgoing to pull the wheels tomorrow to verify that the calipers are straight on the brackets and I'll look at the way the bleeders sit too. But I remember correctly if I swapped the calipers the bleeders would be on the bottom. I definitely check it again. Thanks for the info.

[cdowns]

did you adjust the pushrods for proper operation?

[geezer#99]

Did you change the pedal ratio?
With a booster you need about 4.5 to 1 ratio.
Manual brakes have a 6 to 1 ratio.
Easy fix is to drill a hole 1 inch lower in the pedal and move the pushrod there.

[70CHEVYBB]

Are the hoses new?

[Xeen]

Originally Posted by geezer#99

did you change the pedal ratio?
With a booster you need about 4.5 to 1 ratio.
Manual brakes have a 6 to 1 ratio.
Easy fix is to drill a hole 1 inch lower in the pedal and move the pushrod there.

+1

[tony58]

Originally Posted by supertrkr

Hey guys. I'm having trouble with nailing down a brake issue. So here's the skinny.
1968 C-10 with manual brakes
CPP Disc brake conversion rotors calipers and spindles.
CPP 1" bore disc/drum aluminum master with prop valve
Ford 9" out back with drum brakes

So here's the issue and what I've tried. My pedal is garbage. The pedal goes 3/4 of the way down before the brakes start to work. I've bench bled the master 3 different times. I used a power blender to bleed 3 16 oz bottles of brake fluid the the system. I clamped off all the brake lines and the pedal is rock hard. I unclamp the rear line and the pedal goes down about 1/4 inch. I reclamp the rear line and undo the front clamps and the pedal goes back to crap. The rear brakes are adjusted up. I know that's telling me that there is a problem with the front somewhere between the clamp and the caliper. Has anybody experienced this? I spoke with a CPP tech and was told I had a problem that had them stumped. Basically they sold me a longer rod and clevis for the pedal against my better judgement. Any advice would be GREATLY appreciated.

I would suspect the cheap Chinese master to be bad on the front circuit. Make certain you have it plumbed correctly, the front port goes to the front brakes on that master. I'll bet if you go buy a 1" bore master (not from CPP) and change it it'll work

[supertrkr]

Originally Posted by geezer#99

Did you change the pedal ratio?
With a booster you need about 4.5 to 1 ratio.
Manual brakes have a 6 to 1 ratio.
Easy fix is to drill a hole 1 inch lower in the pedal and move the pushrod there.

The truck is originally a manual brake truck. Feel free to correct me if I'm wrong but the pedal ratio should be correct. It had 4 wheel manual drum brakes from the factory. With that being said the ratio should be correct?

[supertrkr]

Originally Posted by 70CHEVYBB

Are the hoses new?

Yes the hoses are new and not flexing when pedal is pressed.

[supertrkr]

Originally Posted by tony58

I would suspect the cheap Chinese master to be bad on the front circuit. Make certain you have it plumbed correctly, the front port goes to the front brakes on that master. I'll bet if you go buy a 1" bore master (not from CPP) and change it it'll work

I'm about ready just to do this just for the hell of it if everything else checks out.

[my67c20]

So when you unclamp the front lines the pedal goes to crap, correct? How far are the pads moving? What is the rotor thickness? Sounds like you are pushing a lot of fluid.

[Xeen]

Originally Posted by supertrkr

The truck is originally a manual brake truck. Feel free to correct me if I'm wrong but the pedal ratio should be correct. It had 4 wheel manual drum brakes from the factory. With that being said the ratio should be correct?

I think he assumed you purchased a power booster with your new master cylinder, I did too.

[geezer#99]

Originally Posted by Xeen

I think he assumed you purchased a power booster with your new master cylinder, I did too.

Yes I did!!
Next question is:
Did you install residual check valves (2# front, 10# rear) or did your new master come with them?

[supertrkr]

Originally Posted by my67c20

So when you unclamp the front lines the pedal goes to crap, correct? How far are the pads moving? What is the rotor thickness? Sounds like you are pushing a lot of fluid.

The rotors are new and have never been turned. As far as piston travel I haven't tore that far into but stay posted it's happening today. Lol

[supertrkr]

Originally Posted by geezer#99

Yes I did!!
Next question is:
Did you install residual check valves (2# front, 10# rear) or did your new master come with them?

I didn't install any valves. The new master came with a new prop valve and according to CPP tech all 3 times I've called I was told I didn't need either of them. But when they say "you have a problem that has us stumped" I'm losing faith in their tech support real quick.

[geezer#99]

You always need check valves unless the master has them already.
The older masters had them in the ports.
They keep the fluid (under slight pressure) in the line and keep air from being pulled in on the cylinders.

[ERASER5]

X2 on the 10# residual valve for the drums. The 2# valve for the front is optional. sometimes you need it, sometimes you don't. If I were you, I would install both and recheck. On some systems, the 2# front residual valve will drag the front brakes. If it does, the heat will keep adding pressure until you are near locked. Rare occurrence, but it can (did) happen.

[supertrkr]

Originally Posted by ERASER5

X2 on the 10# residual valve for the drums. The 2# valve for the front is optional. sometimes you need it, sometimes you don't. If I were you, I would install both and recheck. On some systems, the 2# front residual valve will drag the front brakes. If it does, the heat will keep adding pressure until you are near locked. Rare occurrence, but it can (did) happen.

OK so the beautiful tech support is full of crap. Lol Now with these valves do they get plumbed before or after the prop valve?

[tony58]

Originally Posted by geezer#99

You always need check valves unless the master has them already.
The older masters had them in the ports.
They keep the fluid (under slight pressure) in the line and keep air from being pulled in on the cylinders.

NO disc master comes with a residual pressure valve. They are commonly used only when the master is lower then the brakes so fluid doesn't drain back to the master. Drum masters usually had them, it's to help overcome the high force of the drum shoe springs so the brake shoes move without delay due to high spring pressure. With that said you can install 2lb RPV on disc's but in this case he has a problem and a RPV will just put a band aid on the problem. I still say the master is faulty, buy a cast iron 1" bore master and try it, worst case you're out $30 if it doesn't solve the problem. CPP should be sending you a new master but they hate having to warrant their junk Chinese parts.

[supertrkr]

Originally Posted by tony58

NO disc master comes with a residual pressure valve. They are commonly used only when the master is lower then the brakes so fluid doesn't drain back to the master. Drum masters usually had them, it's to help overcome the high force of the drum shoe springs so the brake shoes move without delay due to high spring pressure. With that said you can install 2lb RPV on disc's but in this case he has a problem and a RPV will just put a band aid on the problem. I still say the master is faulty, buy a cast iron 1" bore master and try it, worst case you're out $30 if it doesn't solve the problem. CPP should be sending you a new master but they hate having to warrant their junk Chinese parts.

Plus they're a P.I.A. to get a hold of. If I went with a master from a manual brake 69 corvette and used the CPP prop valve, would that combination work?