History:
51 F2
New lines, new hoses, new springs, new wheel cylinders, rebuild master, new front shoes.

Last weekend I took it out for a drive and noticed the brakes would fade pretty bad after about 20 minutes of driving.

Today, I replaced the front shoes(as the back ones are back ordered) and drove it. Brakes were AMAZING.....for the first 10 minutes. I am talking lock up the tires and all. After about 20 minutes of driving, they started to fade to where I felt unsafe so I came back home. All the pads rub minimally when the drums are rotated.

Rebled the entire system. Took it out again and the same thing. First 10 minutes are amazing, after that.....the fade kicks in.


What can be some causes that I can start looking at?

I DID NOT get the drums turned as they feel great and I can not feel a lip with my fingernail.


Also, when I rebuild the master, there is the rod that connects to the peddle that appears to be adjustable....any rule of thumb on that?

 

Chances are you have the shoes adjusted too tight and they're rubbing too much, getting hot and fading. You also want to make sure the rod to the master cylinder has a little play in it so there's no pressure on the plunger in the m/c while driving. That could also cause the wheel cylinder to activate and apply pressure to the shoes, causing the same symptoms. Finally, make sure you aren't one of those guys who drive with one foot on the brake pedal all the time. You see those people driving down the freeway with their brake lights on. ;p

 

Going to double check the shoes this week and back off a tad. At what point should you feel the brakes grab when depressing the pedel? It starts to grab id say almost 3/4 the way down.

 

 

 

How hot are the drums after driving?
Do you have an axle leak?
Are the backing plates grooved? Grooved backing plates restrict shoe movement.
Driving habits.....do you "ride" the brakes?
Denver??Mountains... Double clutch down shift....let the transmission do most of the slowing, apply the brakes for short bursts...let off apply...let off.

This is how I adjust brakes....

With the wheel up after adjusting the star....
I grasp the tire at the top. With just a little force but mostly gravity I rotate the the wheel, letting it go at the bottom. It's a natural motion....After I let the wheel go...
It should make One rotation.
Your brakes may not be adjusted enough.
Plan to do this several times. The shoes may not match the the drum. The friction material has to wear away enough for full contact. It may take several driving and adjustment sessions.
Drive....Check for excessive heat and odor....adjust...repeat.

 

My experience was very similar in the beginning...
In my case, it turned out that one of the brake line connections would leak but very slowly - it would take maybe 2 weeks for my brakes to fade. I thought I'd be doomed to bleeding brakes for the rest of my life...
Nope, one day I asked my wife to get inside and "pump the brakes but this time I asked her to hold them down with as much pressure as possible" and that's when I saw the leak. It wasn't much, but boy it made a difference.
To this day, I have NEVER had to mess with the brakes again - I do hate all the brake dust on my white walls for sure!
Paul

 

Typically brake fade happens because of heat.
On drum brakes if you ride the pedal a bit, the shoes will heat up, and in some instances you will literally have no ability to brake until you get off the pedal and let them cool.

It sounds like you are having a problem with residual contact causing heating, (The reasons for which are already listed above)

I would especially check for grooving on the brake backing plates.

Kirk

 

Do you have a brake pedal return spring? Without one the pedal can cause brake drag and fading.
Mark

 

I had a 50 Coupe that would drag the brakes.....
The longer you drove it, the worse it got.
I had it parked in the parking lot where I worked, a fellow comes in....Nope lights were off but just sitting there the brake lights were activated....

I had a flawed master cylinder casting. There is a check port that lets fluid back into the master. It was spotted but never drilled through. Thbis allowed pressure to build up and apply the brakes after 10-15 minute of driving. Also the brake lights would activate 15 minutes or so after the car was parked due to pressure not being able to return to the master.
An 8th or 16th drill (been a long time cant remember which) cured the problem...completing the spotted hole.

A missing or a weak return spring on the pedal will do similar as mentioned in another post.

 

There also needs to be free play in the pushrod/linkage when the pedal is returned. Otherwise fluid can't get back to the reservoir, or get from the reservoir into the system.