Why - only one caliper works

[Shugalou]

Ok guys in my ongoing saga to get the brakes work I am still having problems.

I can get pedal pressure - but not firm.

Everything is new other than rotors and pads there was plenty of material on them. (New booster, master, lines, prop valve, stainless lines, calipers, wheel cylinders spring kit)

Front right caliper will grab and hold the rotor.

Front left no resistance (nothing on the rears either). I have checked for leaks, bled and re bled and re bled - no bubbles just clear fluid.

I have a new CPP prop valve but there are no leaks.

I am at a loss and am trying avoiding have it towed to a shop...

Can it still be air in the system or is something not working right

[Shugalou]

Something I just thought

I guess I could remove front left caliper and see if I pump if the piston moves

These are remanufactured units - and they are supposed to match the rotor size (heavy duty brake option supposedly) do these units fail often?

Thanks guys

[70CHEVYBB]

Have to ask. Is the bleeder on the top of the caliper on the lefg side. I have seen many calipers on upside down

[Shugalou]

Yes 70 bleeders are on the top and on the correct sides - I have been doing much reading with all the problems I've been having and when I replaced the calipers I was able to avoid this mistake.

While I was in bed thinking about the problem I recalled that this caliper didn't allow the brake pad to side flush against the piston and some material needed to be ground down on the caliper to allow for proper clearance...I wonder if this could be causing the issue?

I'll try to inspect later today

[Keith Seymore]

Originally Posted by Shugalou

I guess I could remove front left caliper and see if I pump if the piston moves

Be careful if you do that. Put a wood block or something in there, otherwise the piston can come all the way out of the bore.

K

[Shugalou]

Thanks for the heads up Keith will do - I guess give it an inch or two clearance to see if I can get it to come out?

[Shugalou]

When I just inspected I could move the inside pad just a touch - this leads me to believe that the piston isn't coming out at - this was with the pedal pressed down and pressure built up.

[f.monroe]

Just for clarification. Did you replace the rubber hoses that go from the frame to the caliper. If not its probably collapsed internally. If you did then you probably have a bad replacement hose , caliper or something.
Good luck with it.
Frank

[Shugalou]

Thanks for the advice

however I have replaced the rubber flex lines with Russell stainless lines.

I'm wondering if remanned calipers are known to fail?

[71swb4x4]

Originally Posted by Shugalou

I'm wondering if remanned calipers are known to fail?

Everything is known to fail. Brand new stainless steel lines, calipers, refrigerators, chainsaws...you get the point. Don't look past something just because it's new.

[Dead Parrot]

Sounds more like either a bad MC or bad Prop valve.

IIRC, 68 and newer brake systems are designed so that any one failure will not cause a complete loss of stopping ability. Many years ago I put that to the test when my 68 Impala blew the left front hose. Right brake still worked. Don't remember if the rear brakes worked or not.

[Shugalou]

Parrot I have a 78 and I think with this setup if there is pressure loss in one of the chambers it will close off (pop the pin out) either the fronts or backs.

This is setup front and back larger part of the MC is for the front disks.

I called CPP tech line (very helpful) and he suggested it could be a faulty caliper. He recommended swaping calipers and bleed with bleeders facing up before attaching. If I can get the other caliper working on the left side I know I have a frozen caliper.

[Shugalou]

Yeah I know everything is prone to failure...ha this brake job has been one failure after the next...I'll be checking the calipers tonight if I can.

[Shugalou]

Ok guys a bit of an update.

So I took the suspect caliper off and found that it looked like the piston was partly coming out at the top. I took a look at the brake pad and sure as **** it wasn't seating properly against the non piston side. So part of the brake pad stuck out. I took off other side and tried those pads and no luck either.



So I grinded down the brake pad points hoping that would fix it. I was worried if touched caliper it would be less easy to return. Well that didn't work so I had to grind the high spots down



So I get these down to a point where the pads seat properly. I'm all excited to test everything and I think to myself - if there was offset pressure due to that bad seating could it have damaged the bore or seal. So I rub my finger over it and...



I'm guessing this is screwed now? I'm thinking I'll try to return it for a new reman. Pain in the ass

[foamypirate]

Just an FYI, those sections you ground down where the pad wasn't seating, are supposed to be like that. There are two small tabs on the brake pad that you need to insert into the caliper, and then that top piece that wasn't seating where you ground the caliper down should be somewhat tight going in. Instead of grinding the caliper to fit it, you should have unbent the two small tabs a little bit. Those tabs are what hold the pad tightly into the caliper, otherwise you'll get clicking on stops as the pad moves around. That pad doesn't move inside the caliper, it moves WITH the caliper, so it needs to be held tightly in place.

[Shugalou]

Foamy thanks for the heads up - Yeah I could see the purpose of the tabs so I didn't grind them off but ground the underside to see if they would fit.

I took the caliper back and got a replacement no problem and the pad fit fine.

So later on tonight I will install and bleed and see if that fixes the prob

[Shugalou]

I installed the new caliper thinking this will fix everything...

Well it was weird while bleeding no clamping force on either side. Eventually I got some clamping and I thought OK it's just a bit more air to expel. Then I couldn't get clamping force again on the rotors.

bled both fronts multiple times and still no better...

do you guys have any suggestions?

[foamypirate]

I'd look into exchanging the master cylinder.

[piecesparts]

Originally Posted by f.monroe

Just for clarification. Did you replace the rubber hoses that go from the frame to the caliper. If not its probably collapsed internally. If you did then you probably have a bad replacement hose , caliper or something.
Good luck with it.
Frank

Yes, that is what I was hoping to see sopmeone say.

[Shugalou]

Well I already ruled out the bad caliper.

I am beginning to wonder if the master is bad if I stroked it too much ha ha. Friggen jack off faulty replacement parts

[mrolds88]

Start bleeding the whole system. Loosen the fittings at the M/C and work your way down the system. Every joint. One at a time. Slow single "pumps" per each fitting. Don't "pump them up". Any air in the system will scatter and you'll never get pedal.

[Shugalou]

Mr Olds,

Thanks for the tip, I was pumping them up prior. I wonder if that was my prop.

I will try your suggestion over this weekend and hopefully report back with some positive results.

[Shugalou]

Over the weekend I was able to build up some pressure and when the brake are applied the fronts now grab. I still don't have correct pedal and the rears aren't working...at this point I think it has to be air in the lines and adjust the rears along with the emergency brake cable.

[KQQL IT]

The proportioning valve is stuck.
Took mine apart, recentered the valve, gravity bled. Finally got brakes on my 73.

[Keith Seymore]

Originally Posted by KQQL IT

The proportioning valve is stuck.
Took mine apart, recentered the valve, gravity bled. Finally got brakes on my 73.

x2. That was my thought as well.

K