under floor brake wil never bleed..any ideas?

Just to be clear... the bleeders are on TOP of the calipers, correct??

 

Maybe its time to cap the lines going to the front or rear to isolate where the leak is?

 

Some thing to try.
Jack up car and see if you can get front wheel to hang.
Now just crack one bleeder little and pump till fuild comes out.
Now see if you can get it to drain out by graivty.
Always keep MC full.
Now do other side. must drain on own.
now let rear to hang do same.
If that does,nt work get another MC.

 

The fact the system has never been right might be the result of how/where the pedal assembly was installed. Did you ever check to make sure the master cylinder can be fully stroked (both systems open) before the pedal runs out of stroke, or hits the floor? This has to be verified, or you'll never get a good bleed.

Also, make sure the booster push rod has about .040"-.050" clearance with the primary master piston. This check should be made with full available engine vacuum, normally 20"Hg, in the booster.

 

Ok, Yes the bleaders are on top.
Ill give the idea a shot and do some measureing.
I never did try to blead it while running..the wifes scared to sit in it alone while running!

 

Chubbie,
I want to give Jason's method a shot but I've got a question before I start it.
On the first cylinder "pressure it with the syringe full of fluid" means till I see it start to fill the MC? I ask because I'm confused when you go on to say "now to the other side
THIS TIME pressure till your wife sees fluid above the holes in the master cyl."

Thanks,
Terry

 

It is usually recommended to "bench bleed" master cylinders before installing them on the car. It is possible that you have air in the master cylinder still.

I will read the rest of the thread and see if I have any other suggestions.

Brian

EDIT: Are your residual valves pointed the proper way for the flow? Im not sure how yours are marked, but it should be labeled.

 

I had a car with the same problem. I bought a power bleeder that clamps to the top of the master cylinder which you put pressure to and forces the fluid through the master cylinder and too the wheels as I went through everything you did. I cranked the pressure higher than recommended and I found a leak at a fitting. It did not show until the pressure was high enough to expose it. Hand pumps to not build enough pressure to find the leaks that are slight.

 

bad front hoses and check the rear hose too for swelling

 

Have used the syringe method with good success also-just crack the bleeder you are pushing fluid through-start at the right rear,left rear, front right,front left (assuming left hand drive and MC on left side of car) push the fluid back into the MC-sure gets the air out of the system

Also not a fan of DOT5 Fluid-I had trouble getting a firm pedal and when switched out to DOT 3-life got better in the brake department.
one more thought..
Have you confirmed the correct pedal ratio??

 

1" m/c bore sounds small for 4 disc calipers.
Pressure bleed from either m/c, or w/c should eliminate all air.

Bruce

Works good
lasts long time

 

OTerryO!!
yes i know i ramble on.....here work with me you should always bleed the furtherest from the master cyl.( i dought it makes a difference) so say, start at the right rear. all you have to do is preasure past the "T" ( i make sure im long past the "T") go to the other side of the rear and preasure till you are sure you are into the master. the process is the same for the front. one syringe full should fill a wheel cyl. all the lines and the master cyl. if it doesn't. you can't stop and just fill the syringe.. because now you have air again, right?? just like when you preasure the second side, you will have air between the brake fluid. so make sure you don't stop just because there is b fluid in the master..keep preasure on till you are sure your second push is thru. try it!!

 

Master cylinders will bleed themselves but the push rod has to be adjusted so the small is exposed in the cylinder when there is no pressure on he brake pedal. Have you adjusted this rod correctly or did you not know about the adjustment.

 

When I replaced my master cylinder and all the brake lines last, I first bench bled the master cylinder, then installed it after I had all my brake lines in place. I cracked open all the bleeds at all the wheels just a bit and pumped the pedal till I could tell it was building some sort of pressure. I then closed off all other wheels except the one with the longest brake line run, had someone else in the car pumping the brake till I could hear/see no more air coming out of the line. Repeated this process in the order of the length of brake line about 4 times. I agree with others, if this bleeding process is not working... then sadly, you must have a bad part somewhere

 

Yes!! Is this just an assortment of parts or is it parts matched to work together?? A brake system is just that, a SYSTEM. At a factory the parts are DESIGNED to function as a SYSTEM. Does your little booster run out of vacuum (stroke) before it can stroke the master cylinder sufficiently?? Does the master cylinder have enough stroke & diameter to fill the calipers??

One person said,"I cracked open all the bleeds at all the wheels just a bit and pumped the pedal till I could tell it was building some sort of pressure...................".

When you do this you are sucking air into the system. Never let the pedal up with any cylinder (caliper) open.

As somebody mentioned, a fitting can leak without showing without pressure on it. There is almost no pressure with a bleeder screw open. Air will suck in through a leaking fitting that does not show even under some pressure.

 

Those underfloor kits they don,t have any way to hook a return spring.When the pedal is up the lever should be at rest hitting the bottom of floor.
You want to use all the travel it has and very little free play to MC.
When I said let it run i meant let graity run to no air seen.

 

A good tip here. You may also want to wash down every related surface with water (let dry or blow off with compressed air) so they're clean, then you may see that minor seepage if it exists.

Look for any funky loops in the lines that may trap air. But your RVs should overcome that.

Another good one is to drop your calipers and wheel cylinders below the master level temporarily and bleed it. Use c-clamps on the wheel cylinders and place a block of wood between the pads in the calipers.

Bob

 

You are a lucky man. I can't keep the wife out of mine, the upside is that she wins and doesn't break stuff.

 

If any part / line is higher than the master, use residual check valves as close to the master as you can get them.

 

I just put an entire Wilwood system in my 56 F100. I put my master on the firewall so I did not need residual valves. If your master is lower than the calipers then you will need the 2 lb residual valves. Be sure to install them oriented correctly. Bench bleeding the master is a must. The master came with a kit that had two clear hoses that were routed back into the master reservoir I noticed that when I bench bled, the master would push and pull fluid in and out of the reservoir. Keep pumping until you see no more bubbles. The master must be level when bench bleeding. Good luck.

 

You may have to refine your approach and change your prospective.
Start at square one and assume everything is suspect until you verify its correct, VS - everything is fine until you verify it being wrong.

Square one would be checking for matched components.
Two, pedal ratio and adjustment of rods.
Bench bled, capped and tested master independent of system.
Inspection of all fittings and flairs. Burrs on the brass or crooked flairs cause trouble. The threads do no sealing, its the mating surfaces.
RVs for proper orientation and operation.
Then start the bleeding procedure.

It's not that hard to out smart brake fluid.

 

I didn't have a problem with the pedal arm returning until I mounted a '52 Chevy mechanical brake light switch under the toe-board. The effort required to overcome the internal spring on the switch was so great that I either had to come up with a remedy or drive around with the brake lights on and pedal partly depressed.

Here's what I did;

I'm not a technical writer, but here goes;

I got two washers (one that is a little bigger than the MC bore, and a smaller one that fits tightly inside the small end of the rubber boot) with holes in the center that are just a bit bigger than the push rod. I put the small washer inside the boot, pushing it all the way to the end (the way my push rod is set-up with a heim joint the small end of the boot rests on the lock-nut). Next I stuck the push rod through the hole in the boot and the washer that's inside. Then I put a small coil spring over the rod, inside the boot (the coil spring needs to have an ID that's just a bit bigger than the push rod's OD and be the correct length and spring rate for your application). Finally I put the big washer in place over the rod and inside the boot, placed the rod inside the MC, attached the boot to the MC and
bolted the heim joint to the pedal arm.

To simplify...........the coil spring over the push rod is pushing against the MC and heim joint lock-nut, with the big washer keeping the spring from entering the MC bore and the small washer protecting the boot.

My pedal now fully returns and everything is inside the rubber boot nice and neat.

 

unkledady I think we did about the same thing.
The adjustment nut on push rod bent piece of medal 90degs with hole for return spring and hooked to frame.This was a kit for the 39 ford and i to used a 52 chevy brake switch.My brake lights were on till the re turn spring.I had a speedway mc i couldn,t get to bleed and it was junk,got a NAPA one and good to go.

 

When you bleed it out take some line clamps and pinch off all the flex lines. If the pedal stays hard and doesn't bleed off when you let it sit then you know the system is good from the pedal to the clamps. If it is still going soft then your problem is between the pedal and the clamps. This will help split the system in two in a diagnostic sense. If the pedal stays up with the flex lines clamped off, release the clamps one at a time untill the pedal goes soft this is the part of the system that is giving you grief. Then you only have to diagnose from the clamping point out to the caliper on that branch.

 

We get spanked at work if anyone EVER pinches a flex line. New or old.
It could break the inside liner!

 

yup. also consider plugging off fronts or backs to eliminate 1/2 of the system at a time. narrow down your problem. good luck...jack

 

you are emptying the m/c before getting full pedal

your pedal should be firm near the top of its run

your firm pedal could be the bottomed out piston

check rod length and petal swing

start over

 

Ok.not much time to work on it this weekend but I checked with wilwood and I need the residue valves 2 lb for disc and yes they are in the correct direction.
I checked for leaks, re tightend everything measused piston/pedal travel. blead it again. same thing .
Its pumps up and stays firm..put the tools away and test it again and its almost to the floor....then riped my hair out and the wife too away the crow bar I was going to beat the car with!