Front Disc Brake mission impossible

[ebanville]

Here's the story. Installed a CB Peformance Wide 5 FRONT disc brake kit on my car in 2004. Only 10,000 miles on the brakes. Rear brakes are stock drum. Brakes were working fine when I pulled the transmission for some needed work. In replacing the clutch cable during installation of trans I pulled out the master cylinder pushrod to find it wet on the tip. Sure enough, leaking master cylinder.

Replaced it with German FAG master cylinder, bled the hell out of the brakes. Couldn't get consistent pressure. Bled them again and again with the pedal method, pressure bleeder and vacuum method. Same issue. Brought it to brake specialist and they spent hours working on it. No leaks anywhere. But poor brake action and pedal that goes all the way to the floor before engaging brakes.

Replaced the rear drum brake cylinders and checked lines end to end and found no leaks anywhere. Thought maybe the German master cylinder was bad out of the box, so we swapped it out with a Brazilian one. No difference. Very little pressure going to the front brakes.

Called CB Performance and they said it might be air trapped in the calipers so to pull the calipers off the rotors and hold the bleeder valve as high as possible and re-bleed. Did that. Still no help.

We thought maybe a residual pressure valve would do the trick, but CB Performance says NOT to install a residual pressure valve. According to them, they're only for FOUR wheel disc brakes. I only have disc brakes on the front wheels. Since my brakes worked before this transmission job, I have to agree with that.

So, any theories? Like I said, there are no leaks according to myself and three mechanics who I trust. They've been bled in every method fathomable. I personally pushed eight liters of fluid through those lines. At this point the mechanics are giving up and giving my car back to me since they're stumped. I'm stumped. HELP!

[57streetrodbuggy]

could you have a hardline that is rusted through inside the tunnel where you cant see leaks?
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[Teeroy]

Hard line goes along tunnel not thru it.
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[getgeoff]

Do you think that any time you were doing some tranny work that you might of pinched one of the brake lines at the rear which would cause a blockage or a restriction??? Because it was working fine untill you did some tranny work..right..

[Luft kühl]

You could try clamping the front soft lines closed with vice grips to see if you can get a firm pedal.

If not, try the same thing with the rear lines. This may help you to determine which brake circuit is causing the problem.

[Hotrodvw]

I had a similar issue, my rear brake line was rotten through, right where it enters the car by the pedals. They rust from the inside.
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Hose & Fittings

[ebanville]

In answer to responses in order.

Checked the lines to see if I pinched one in the back and everything is fine.

Can't pinch the fronts since they're braided stainless but the mechanic blocked off at the master cylinder and got a hard pedal with just the rear active, so it seems like a problem with the front. Then again, the back brakes are adjusted out pretty far (so I could drive to the garage using the e-brake), so it could just be that the little bit of pressure is enough to lock them up in the back.

Re-checked the lines (and yes they run along the tunnel inside the car, not through it) and could not find a leak anywhere. System is not losing fluid nor losing pressure when under pressure from a pressure bleeder so it would appear that there are no invisible leaks either.

[The Noof]

Make sure youhave at least .030 clearance between the brake pedal pushrod and the master cylinder piston.Try isolating the front callipers, one side at a time to see if it's a side specific issue.If not,and the pedal height is the same for both sides, try this:remove the callipers with the brake hoses attached.Pump the pedal untill the pads touch eachother.slowly push the pads back untill the callipers fit over the rotors with drag.Try the pedal now.If it's good, I will explain why.If not, disregard.

[ebanville]

Question about checking clearance. How do you get a feeler gauge in there to check the clearance? Never done it before.

[The Noof]

Can't,bro,but this is where "feel" comes into play:look carefully at the pushrod movement while SLOWLY moving the brake pedal from it's rested position.You should see about 1/4 to 1/2" movement in the brake pedal (measured at the brake pedal pad) before you "feel" the brake pedal pushrod touch the master cylinder piston.Look carefully when you do this, and make sure you're not feeling the play between the pin on the brake pedal that the pushrod mounts on, and the inside diameter of the pushrod itself.

[ebanville]

Thanks Nuff. Will check it in the morning. And will follow with doing the caliper bleed you spoke of. I'll post what the results are.

[ebanville]

Sorry, I mean The Noof.

[earthquake]

ebanville
Did you bench bleed the master before you installed it? I have heard that you can get air trapped behind the brake pressure switches, have someone press on the brake pedal and loosen the switches and see if there is any air in the master cylinder. I always bench bleed the master by filling a clean coffee can with brake fluid, put the master in the can and pump the pistons with a 3/8" extension untill there are no more bubbles, then clean the up with "Brake Clean" after, this works for me.

Earthquake
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[ebanville]

Didn't coffee can bleed it, but bench bled it in the car so to speak. Took someone's suggestion and had everything attached but the brake line going to the back breaks. Depressed the brake pedal, plugged the open hole in the master, then let the brake pedal back up so it sucked fluid in from the reservoir. Repeated until fluid was flowing out of the hole.

I'll add the brake sensor thing to my list of things to try since that's a new idea. Thanks!

[Jengel451]

Also try and crack the line going into the caliper and try and bleed that portion, then move to the caliper.

You didn't mention what style of M/C you have.

What method are you using to bleed? Mitivac? Pump and bleed? pressure?
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[ebanville]

Question about the coffee can bench bleed in case I decide to do it.
Once you've bled it in the can, how do you get it in place without getting more air in it? I'm sure you plug the holes with something, then put it in, but even then, don't you get air coming in as you connect the lines? Or is your method just to try and get out the stubborn bubbles that can hide in the bottom and use regular bleeding to get out the normal collateral damage so to speak?

[rearenddude]

maybe in left field here:

is the hand brake correctly adjusted? two-three clicks and there on?
had a similar issue, i had left hand brake disconnected after some service.
nearly all of the cylinder volume was used to displace the rear cylinders to the point of contact leaving next to no pedal left to generate pressure.

[ebanville]

Style of master cylinder would be a dual circuit type 1 '67 on according to the Wolfsburg West catalogue and same for the Brazilian one which I got at small car performance in Torrance. According to CB Performance, that's the type of master to use. It's also the only type I've ever used with this system and never had a problem like this.

As for the bleeder, it's a pressure bleeder I got from CB Performance. I learned the hard way about pumping it up to high. Got it up to 17psi and it popped off the darn reservoir and brake fluid went everywhere.
http://cbperformance.com/catalog.asp?ProductID=1184

The mechanics at Funk Bros. tried pedal bleeding, pressure bleeding and vacuum bleeding as well and same lack of result.

[ebanville]

Rear brake shoes are adjusted so that there's a way heavy drag when you try to turn then with your hand. When you pull up on the e-brake it clicks four times and that's it. Also, the e-brake cables are tightened all the way down.

[myb356]

Do the front calipers have two bleeders?....and are you bleeding the lower? (lower bad-upper good)