HELP! Residual valves

I need some help with residual valve before I go nuts.

I bolted a power dual master cylinder on my 41 Chevy (stock drums).
Everybody and his kid brother told me I need to have to 10 lbs residual valves in the lines.
So I added 2 valves.

What happens is, it brakes fine but it doesnt stop braking.
I adjusted the brakes as usual, but every time I hit the brake it doesnt relase, but blocks the wheels.

Any ideas?

Thanks, Frank

 

if the master is under floor,you need 2 lb in front and 10 in rear.

 

Also check the length of you push rod on the master a fraction too long and it will do this (but usually start out OK and after some driving get worse)

 

I was told 2 lb for disc brakes and 10 lb for drum brakes...

 

Yeah I always was told 10 kbs for drums.
The MC is lower than the wheel cylinders - that´s the reason for the valves, so they said.
I will check the length of the rod, but cant imagin what that has to do with it, but what do I know?

I dont know if this maters, but the brake switch (juice) is also "stuck" after I hit the pedal the firts time. That means the brake light stays on.
Maybe just deflective. Who knows? I saw them already broken, out of the box.

Is it possible, that the MC already has valves?
It´s one of those Bolt in kits with braket and all fo 41 Chevy.

Frank

 

take the valves off and give it a try, if it works fine then leave them off. i had trouble with them keeping the brakes on in a 29 chrysler, took them off and no more draging. with the brake pedal released then the rod should be loose.

 

I have 4-wheel disc brakes and have 2lb valves on both front and rear... I had a problem with the front brakes once they got warm that they were constantly engaged... i took the valve off the front and ran a drill bit through it so that it was completely open... my MC is just about level with the front calipers...

 

It's quite possible that the MC already has internal residual valves in it, many do. Also check the pushrod length, if it's adjusted out too far, it won't allow the piston to fully retract and will keep pressure in the line.

Edit: oops, Russco beat me to it...

 

With drum brakes he needs 10 psi in both.

 

Sounds like your linkage is sticking, and not letting the pedal return all the way. That would keep the brake lights on too.

 

Ck valves are not the prob. For one reason or another the M/C piston is not returning all the way. Could be the pedal pushrod/linkage to the booster or the pushrod from booster to M/C . Had a weird prob one time the piston retaining snapring in the M/C had one ear bent not letting the piston return all the way ,same symtoms. You do have a return spring on your pedal right? Make sure the pushrod has a bit of free play to the booster. If it does back off the nuts holding the M/C to the booster about 1/8" see what happens then. One place or the other is where the problem is. One other thing to check are all 4 wheels affected? If only 2 problem then could be internialy in the M/C. Let us know what you find.

 

is this piece of crap under the floor brake pedal assembly from those fine folks at mbm brakes?? does it sorta' bolt in..

 

Not exactly from mbm brakes, but I looked up the site and it seems to be the same kind of "bolt in" assembly.

Bolts right in, yeah right LOL. Especialy if you dont have a automatic setup, and need a clutch pedal, but that´s an other story.

Monday I go check the rod lenght and play. I led you guys know.

Thanks a bunch for your thoughts.

Frank

 

Had the same problem one time on a drum/drum setup. 10 lb residuals front and rear. They were initially bled using vacuum pump. Installed 'speed bleeders' and re-bled using pedal pump method (rear first/front last) Problem solved

 

Bleeded the sh....t out of it. Made sure the rod has play.
Still the same.

One more thing, bevore I bend new lines and remove the valves.

The MC is only a view inches away from the exhaust.
Also the lines on the other side are pretty cloose to it.

Is it possible that it´s symply getting fried?

Thanks, Frank

 

Stovebolt : go re-read post 11 ,loosening the M/C to booster. If the pushrod is to long from booster to M/C the brakes will drag. Have seen that happen.

 

do you have the residual valves pointed in the correct direction? in--->out.

 

It wouldn't matter if the M/C already has valves, they are no cumulative so even if you put two of them together, it's still only 10 lbs.
I really think you don't have enough free play in the push rod. I have seen cars that needed a 1/4" of play in the rod. After they get the brakes heated up the play was almost all gone.

 

Check the adjustment rod from pedal, got similar trouble with my setup (disc front,drum rear) , needed some real fine tuning to not drag the brakes, and to engage them right.
If you dont get any change doing this, remove a res.valve a time and check, it could be some inbuilt valve in the MC....

 

I agree that a 10 lb residual valve should not make this happen. I have seen this twice before - once with the pushrod too long (between the booster and the MC, not the brake pedal to booster), the other time was a defective MC with the return port hole not properly drilled. If the MC piston does not return far enough to uncover the port or if there is a blockage that prevents the fluid from flowing back to the reservoir this will cause your problem. Bum check valves could cause that too if they are closer to your master cylinder than the brake light switch.

 

O.K. I adjusted the rod between MC and booster all the way in.
I adjusted the rod from the peddal with plenty play.
Now I have allmost to floor the peddal to get any brake action at all.

Right front wheel is alright now - left still draging. When I adjuste it, it´s fine till the next time I hit the pedal.

Maybe my problem is not the valves but the shoes.
I got Bendix brakes on the rear (short shoe goes fron right?)
And the original Huck brakes on the front.
All my manuals show two shoes with te same lenght for Huck brakes,
but I got a short shoe in the front on those.

May that cause a problem?

Thanks, Frank

 

Has the car sat a while? The front wheel cylinders may be corroded or gummed up, causing them to stick. Also make sure the wheel bearings don't have excessive play and the shoe placement has to do with the brake design, self energizing-short front, long-rear and if both shoes have a fixed lower pivot point I would think the long shoe should be in the front because it is loaded harder on the drum by it's rotation.

 

Yeah, it sat for 3 years, and the cyinders where gummed up.
I cleaned and honed them carefully and put everything back together last week.

Slowly I run out of ideas.

Are you sure with the short shoe in the back for Huck brakes?

Thanks, Frank

 

I can't be sure, just trying to apply common sense thinking to it. You may need to find a manual for that particular model or call someone like this for help http://www.chevsofthe40s.com/

 

Did you ever try removing the residual valve to see if it made a difference? It may be as simple as a defective valve or debris in the wrong place. Also have you made sure the pedal itself is not binding? You can also push the pedal, check the drag on the wheel, release the pressure on the wheel cylinder by opening the bleeder and see if it frees up. That way you can tell if the problem is in the drum (wheel cylinder sticking, brake shoes binding) or elsewhere, like too much residual pressure, master cylinder piston/pedal binding or collapsed hose,etc.

 

Good idea - I try tat tomorrow.