under floor brake wil never bleed..any ideas?

I installed a underfloor brake kit on my 55 5 years ago and it has never been right..finley this year I but 4 wheel disc, a wilwood 1 ' bore master, small duel diafram booster, new braded hoses all around, new calipers and even bought a bleader kit.
it still has air in it. my wife and I blead it 50 times and went through gallons of fluid..I tryed everything and it still feels spongey and the pedal goes to the floor after it sits for a few ..There still can not be air in it ..can there?
Anyone have these issues or have any ideas besides bleading again?

 

Look at the one man half brained tech week winner's entry.

 

do you have residual valves in the system? 2lbs for discs.

 

"Pedal goes to the floor after it sits for a few"...

Definitely grabbing air from somewhere. Brakes have to be air-tight. If it goes to the floor, it's leaking somewhere without a doubt.

If you have a "stronger" pedal at the time of bleeding than a couple of hours later tells you is small...but definitely still there. And if it's grabbing air, then it's leaking fluid. Look and you will find a fluid coming out somewhere if your bleeding gallons of fluid to test it.

 

I had very good results using my Mityvac to bleed mine [underfloor]...
dave

 

make sure all your lines are secure and not hanging loose. I have seen this cause the same things you are telling us about. I know you know what you are doing but also make sure the bleeder screws are at the top of the caliper. Watched a guy bleed his for about a week straight until he discovered he did that by accident. Hope this helps RED

 

i had 2 different cars that took on air with out leaking fluid. one was "rotor run out" the other was a wheel cyl. they are hard to find. a friend of mine( HAMBer) told me about the syringe!!! go to a large animal vet. and get a big plastic syringe. now fit the end with 10 inches of 1/4" hose, i put a zip tye on it to keep it from sliding off. fill it with brake fluid, hold it so the air goes out the top.

with cover off the master cyl. remove most of the old fluid. go to the wheel bleeder and preasure it with the syringe full of fluid. now to the other side this time preasure till your wife sees fluid above the holes in the master cyl. stop. go to the front and preasure one side till you are sure you are past the "T" now to the there side. it sould be bled!!!!!!

$10 bleeder!! none better!! I no longer even bench bleed useing the syringe method! THANK YOU Jason!!!!!

 

Here's a couple of pictures of the syringe. Nothing could be easier. anybody want to buy a piece of shit mityvac?

 

Just to be sure, Did you pre-bleed the master cylinder before you installed it?

After 50 tries you should see fluid if you have a leak. If not then I'd call Wilwood and talk to them about the residual valves and the possibility of a bad MC.

 

I had this problem with my studebaker wagon.. losing peddle that is.. What is on it for calipers?? later GM ones have what they call Zero Drag calipers.. you will never get a older master cylider(MC) to work with them.. you need a late model MC to go with the Calipers.. S10 were bad for this..I ended up putting a S10 MC on it to fix the problem.. as for air you need to preasure bleed the system. if you have any line that are higher then the MC then air will hang up here and you will chase it for ever.. preasure bleeding will get the air..

 

That syringe trick is the greatest bleeding idea EVER! Is there a particular order you should do each wheel?.. I vacuum bled mine and it took a few tries before i had a happy pedal.

 

I had condition similar to what you describe with my 32. The master I bought was suppose to have residual valves "built in"..................... it did not. I finally put a pair in it and has worked great since then.

 

A spongy pedal can be caused by the master cylinder being too small. It runs out of fluid pressure before the bakes are against the rotors or drums. The master cylinder does not have enough displacement.

 

I had this problem in my model A, changed out to a larger MC...BRAKES!!!!

 

the syringe will push or pull brake fluid, but the preasure bleed works best. to answer.. they say start the furtherest from the master, and work towards it. so thats what i do. we kind of make up the rules as we go. the best part of the syringe "preasure bleed"is i no longer bench bleed master cylinders. just put them on and preasure them up!!

 

I'm gonna vote residual check valves on this one. The key being under floor master cylinder. When the calipers and wheel cylinders are above the master, gravity has a tendency to drain the fluid back into the master. This is what the aftermarket check valves are intended to do. They hold the fluid and a small amount of pressure back in each line going out to each corner and prevent drain back.

 

I had a problem getting my Merc's brakes to bleed completely when I put on front disks and an under floor master cylinder. Since mine was a dumb mistake, maybe no one else is thinking of it. I mounted the right side disk on the left, and visa versa. The result was the bleeder valve on the disk cylinder was not at 12 o'clock, more like 10 o'clock. After I tried every bleeding technique me or my buddies could think of, I called the manufacturer who told me the disks were misslabeled. But i should have figured it. Bottom line, make sure the bleeders are as close to straight up as possible!

 

+2 on the RPVs. drums all the 'round and a MC under the floor and it stops great. And hey chub, i kinda make it up as i go too. Must be somethin to do with growin up in iowa... Council bluffs til i was old enough to run for it.

 

Thanks for your help guys.
I would bet on the residuel valves also, but it says nothing about it on the wilwood papperwork si I will need to give them a call to find out if they are built it or needed.
Its the only thing I can think of. I belead them with the motive pressure bleader through the master and through the calipers and the same with the pumping the pedal way. i even cam up with a way with a clear hose into the fluid bottle to pump out and suck up the fluid so I can watch for air.
there is no air in the system when bleading but there is when it sits and I need to pump it back up.
I replaced every brake part 2 times now I have the best of parts and the same problem.
If it were sucking in air it would leak fluid under pressure..correct?
Im almost at the point where I stck it all back up on the clean and smoothed firewall..that would suck.

 

Since you have all new Willwod parts this anecdote probably won't apply. A long time ago I rebuilt a master cylinder and tried about a hundered time to get the thing to bleed. I just couldn't get enough pressure. Finally I matched the old piston to the new one and found the new one was shorter. Back to the parts store, got the right piston and ...problem solved!

 

Cooking syringes are also a great source.

I want one of these babys!

 

Under the floor master cylinders have worked for years.There is no reason to blame the location of the master cylinder. Vern Lacy from the early v/8 garage is on the Ford Barn. He sells brake kits for old Fords. Post your problem on the Ford Barn v/8 site and he will probably reply. You might title your post "Vern Lacy brake problem". I think his website is Early v/8 Garage. He is in California. I still think the master cylinder is too small or the brakes need to be adjusted tighter. I hope you tells us what you actually did to correct this problem.

 

"and went through gallons of fluid"
Please advise what brand of fluid you are using, I want to buy stock in the company. The spongy feel may be air in the line, but the pedal to the floor after a few is a residual pressure or a bad MC problem.

 

like i said before...i had 2 cars that took on air and didn't leak fluid. the 1st one was rotor run out the other one had a bad wheel cyl. it was new and every thing was painted or powder coated... so i knew it wasn't leaking. i started changing out parts some lines i was on my 3rd try! till i changed out the last piece

 

Look real close at your calipers and make sure that the bleeders are on the top. It is most common on front calipers, sometimes you will find one that the bleeder is on the bottom, if that is the case it will never bleed.

 

One thing about the residual valves is that they don't just hold pressure and keep the fluid from draining back.They keep a little pressure on to hold the seals tight against the pistons in the calipers and wheel cyls.I would never build a car with an under floor mc with out residual valves.

 

Good info/food for thought. I just finished bleeding the brakes on an old lincoln that only has a proportioning valve. What a chore, with fingers crossed I got it right.

Problem on the old Lincoln that I ran into is that the instructions that came with the hydraulic booster were to not bleed the master, so dummy that I am I didn't bleed the master first. That is a lot of damned air to pull though the brake lines, I'll bet the master got filled a dozen times at least before I was pulling a solid stream (I use a vacumm bleeder, I am now getting anchors tatooed on my fore arms so when I wink I'll look like popeye).

 

You need residual valves in the lines to keep the fluid up in the calipers.

 

I to believe it's lack of RV problem but it's easy to eliminate if it's the M/C or not, plug the outlet holes and push on the brake pedal, is it hard? Hold pressure or does the pedal go down? Let sit hit it again, hows it feel? This will only tell you the condition of the seals in the M/C and or trapped air in M/C.

 

I have the corect residue valves and a adjustable prop valve.
Can not be the master because it did the same with the corvette master as the wilwood.
Its a bit better than it was but with all new parts it should be perfect.
I can pump the brakes and it feel like the pedal stays up ,but I put my tools away come back and its down near the floor again.