Brakes: 1950 Champion; Will not maintain brake peddle

[Buddyfaulk]

I have a 1950 Studebaker Champion. The hill-holder has been removed.

I changed the master cylinder, rear brake shoes and the wheel cylinder on the passenger side.

I have bleed the brakes and can achieve a firm peddle, however if I let the brake peddle return it's normal position and wait 30 seconds, when I press down the peddle goes to the floor. Then I have to pump the peddle to have brakes.
What is my problem?

[RadioRoy]

It's likely that you still have air in the system, or your shoes are not adjusted properly.

[63t-cab]

Did You Bench Bleed the Master Cylinder ?

[Buddyfaulk]

Did You Bench Bleed the Master Cylinder ?

Yes, I did bench bleed the master cylinder and all for wheel cylinders. Several times.
Being the hill holder was removed. Would this have an effect on the brake system?

[jclary]

A few thoughts...Although I've never experienced the problem, we've had others to mention making sure your master cylinder rod is adjusted with enough "free-play" that the master cylinder piston can fully return. Also, make sure your master cylinder cap vent is clear.

For brake adjusting...always adjust the cam until the wheel locks. Then back it off until you feel a tiny bit of contact. If your brakes are original, that goes for each shoe. Even with the automatic adjusters in place, you need a good initial adjustment.

For bleeding...did you have someone to pump your brakes up for bleeding, or did you use one of those bleeder bottles, or the Mighty-Vac bleeder pumps? I've experienced a situation where those bleeder tools are not aggressive enough to purge all the air. There are places, where air bubbles will not purge without aggressive pressure. What happens is that an air bubble sits in a high spot while the fluid moves under it. Only someone with strong leg pressure, applied to the pedal, when the bleed screw is opened, will the air bubble be dislodged and flushed out.

I had a situation with a spongy pedal that always had to have a couple of pumps when coming to a stop. It never went to the floor, but only got a good pedal height with a pump or two. Usually working alone, I tried the little gravity bottles, and the Mighty-Vac. After several bleeding sessions, the result was always the same. Finally, I enlisted my ex-college football player son-in-law, to pump the pedal for me. It worked. Enough pressure to dislodge all the air, and I had full reliable braking.

[TWChamp]

If the pedal feels firm on the second pump, then I'd think the shoes need to be adjusted tighter.

[nvonada]

It sounds like you are saying the pedal goes to the floor on the second pump. Sounds like something in the master cylinder to me. If all else fails you can buy some 1/8" pipe plugs and plug the outlets to the master cylinder. At that point the piston should hardly move at all before getting rock-hard. You can then hook up one brake line at a time to isolate where the problem lies.

Nathan

[345 DeSoto]

Bad Master Cylinder...

[StudeRich]

It does appear that either there is WAY too much movement of the Shoes before contact with the Drum or the M/C Piston is bi-passing fluid, New sometimes is NOT Good!

Have you checked the fluid Level after the failure happens? A slow Leak in the lines or other location will cause this.

[Buddyfaulk]

I would like to thank everyone for their replies.

Car Condition:
1950 Champion Studebaker
Hill-Holder removed by previous owner.
Brake lines leaves the master cylinder with a 3/16" line. Connects to 4-way brass fitting, one for the supply, one for the rear, one for the front and one other for the brake light switch.
Front brakes shoes are half the thickness of a new shoes

Original Problem:
After driving the car for approximately 20 miles the brakes will apply themselves (with NO movement from the brake peddle) creating a drag. Brake lights are on. The system will self relieve the pressure over night or by relieving the pressure by opening a bleeder valve.
Found that the rear passenger side wheel cylinder had a small leak and the return spring was broken.
Brake peddle adjust was adjusted way to far in. No free play at all.

What I've done:
Installed new master cylinder, part number NAPA-M2796
Flushed all brake lines
Installed new shoes on the rear
installed new wheel cylinder one rear passenger side
Installed new return spring to rear passenger side
Adjusted brakes for all four wheels
Bleed the brakes by vacuum and foot power. Have pushed 32oz of dot-3 brake fluid through the system
Adjust the brake peddle free play to about 1/8"

Problem:
After pumping or bleeding the bakes I have a firm peddle half way of the peddle travel. When I let the peddle return and wait 30 sec to a min when I press the peddle again it moves completely to the floor with no resistance. I can pump the brake peddle several times and will achieve a firm peddle, but only half way of travel. This cycle will repeat over and over.

Plugged the outlet of the MC, Peddle will move half way of its travel before getting a firm peddle, will maintain this over time.
The only way I can achieve a firm peddle at the top of the peddles travel is to adjust the rod about half way into the piston. (I know this is not correct)

Does a Studebaker without the hill holder have a different MC or some type if valve, like an external Residual Pressure Valve? I understand there is a residual pressure valve built into the MC.

I am a mechanic with 30 years of experience. I have worked on a lot of brakes systems, I have never experience something like this.

[StudeRich]

Wow! It would appear that you really HAVE done everything right!

No there is NO difference anywhere on a Car with or without the Optional Hill Holder, except of course the Lines and number of ports in the Brass Block on the M/C.

I am leaning toward the Fact that this IS a '50 Champion with those funky automatic adjusters and non self energizing Lockheed Type Brakes.

So you have ALL of the special hardware correctly installed for the Auto Adjust feature?
How much oversize on the Nine Inch Drums?

[jclary]

How about taking and posting some pictures of your brakes. Especially the front. If the automatic adjusters have been removed, a special cam adapter must be installed.

Otherwise, you'll never be able to adjust the front shoes. I think it's only Champions that reguire those adapters.

[rkapteyn]

Sounds like you need to bleed the brakes some more or your adjusters are not working properly.

[Dan Timberlake]

"Plugged the outlet of the MC, Peddle will move half way of its travel before getting a firm peddle, will maintain this over time."

That sounds like somewhat of an issue, all by itself.

Can you look into the MC to see if the cup squirts and moves over the replenishing port immediately?

==============

Have you been able to test if the pressure still builds up and is applies the brakes over time?

[jclary]

When I made my comments in post #12, I was out in my barn playing with an engine, and checked the forum using my iPhone, (which I absolutely hate, 'cause I have not learned, or gotten comfortable with it). There is an important reason to know all the car's original components are in place. That is the reason for my request for you to post some pictures. Now that I've come in the house, where I have access to equipment I'm familiar with, I will post pics of the special adapter I was talking about in post #12.

Many people do not like the automatic adjusters Studebaker used up until 1953. So, lots of folks tossed them. In order for some models to work as manual individually adjusted brakes... a large "roller" was placed over the car's adjusting cam. It looks like a flat washer, but the manufacturer called it a "ROLLER." I have included a picture of the instructions, a Roller, and the box they came in. The pictured Roller is for the rear, because I'm still using the automatic adjusters on the rear. The front Rollers do not have the "clipped" area and are perfectly round.

Here's the pics...