67 C10 Manual Drum/Drum Brake Help

[A.Bursell]

Hello,

One of my projects on my 67 is getting the brakes in order so I can drive it. I did drive it home and I had about a 50% chance of getting brakes when I stepped on the pedal. I figured it was leaking wheel cylinders (which they all were). They are manual drum/drum brakes. I just replaced the ORIGINAL parts on the truck, and yes they were very worn out.

Cut drums (also drilled the rivets from the hubs), replaced and repacked bearings, new shoes and hardware, cleaned anything reused, new wheel cylinders, new soft lines, flushed brake fluid (which came out looking like MUD but is clean after 5 bottles of fluid) starting with LR and working my way closest using speedbleeders I decided to try.

I thought this would do it, but took the truck out to get the brakes adjusted and it is stopping much better, but it seems I still have similar symptoms. Sometimes I get good brakes, sometimes the pedal will go to the floor when I stop.

The only things left in the system are the hard lines and the master cylinder and what I thought was the proportioning valve. I don't believe the hard lines have a problem or I would see leaks someplace after putting so much fluid through the system. That leaves the master cylinder and proportioning valve. I have been searching around and it seems that the "valve" might be just a switch in my drum/drum application and not have any impact on the fluid.

Long story short, my questions are:

1) Does this sound like a master cylinder problem? (I hope so, since it's the only thing left!)
2) Is the "proportioning valve" just a switch in the drum/drum application -- can it go bad and cause me braking problems?
3) Is there anything I am overlooking?

Help and thanks,

Adam

[cdowns]

there is no proportioning valve in the drum brake systems what u have is just a distribution block

[68gmsee]

Re. questions

1. If all the air is out of the system, the master cylinder is the primary culprit when the brakes go all the way down. Easy and cheap to replace but be sure and follow directions for bench bleeding and rebleeding the whole sytem again.

2. The distribution block used on drum/drum is just that and probably not the cause of your problem with the pedal going down.

3. Looks like you covered all the potential problems.

[Stocker]

You've fixed / replaced nearly everything but the MC, so that would be next. I didn't see any mention of power brakes so I'm assuming they are manual. If power, you might have a bad booster or a problem with the vacuum to it. But I'd do the MC next.

[ole dollor]

i also vote for the master cylinder to be replaced and bench bleed it before you put it on, you may also have to bleed the whole system again....like others have said....they are cheep...but very important ....

[PanelDeland]

Do the MC.Chances are it's bad and even if not,everything else is new so it might get jealous and just quit on you if you don't give it some love.

[A.Bursell]

Great, thanks guys!

I'll go ahead and get a MC. Never replaced one before, but it doesn't look bad. I've read up on bench bleeding, I'll plan to do that and rebelled all the brakes of course. Manual brakes BTW in case I didn't mention.

I would like to know a little more about the distribution block. I can't seem to find replacements anyplace, so it's either really rare that they go bad, or really rare that anyone uses them- or both I guess. Can they go bad? Or is it like the hard lines that if they aren't leaking they are ok? I would really like to know I will have the brakes fixed this time and replace any more possibilities at the same time.

Thanks again guys!

Adam
Posted via Mobile Device

[Stocker]

Originally Posted by A.Bursell

I would like to know a little more about the distribution block..... is it like the hard lines that if they aren't leaking they are ok?

This. Unless it's plugged internally. It's just a chunk of metal that allows all brake hard lines to be connected to the master cylinder.

[c10srule]

master cylinder is bad, when they start sometimes youll have a good pedal and some times you wont, then you dont have a good pedal at all, if its the rear piston itll be wet on the firewall inside the cab where the brake rod goes through, if its the front piston the fluid just bleeds back into the system,

[A.Bursell]

Thanks again, I will get myself a MC and have some good brakes!

Adam
Posted via Mobile Device

[Wrenchbender Ret]

Any time you rebuild brakes on an old vehicle the master cyl. is the first thing to replace. On The old single MC you can generally put a kit in & get by but the dual MC its just as cheap to put in a reman or new. If you have bled the brakes good already & bench bleed the master cyl. it will probable be fine.

[A.Bursell]

Just realized I never updated this thread. I did put the new master cylinder on. Brakes are good. Well adjusted and stopping nicely.

Thanks for your help everyone!

Oh, and for any future searching. My firewall to master cylinder gasket was shot. I found a water outlet gasket at Napa that was a perfect fit. No trimming or anything necessary.

Adam

[Stocker]

Glad you got it fixed, and thanks for the update! Everyone should be that thoughtful...

[68gmsee]

Originally Posted by Stocker

Glad you got it fixed, and thanks for the update! Everyone should be that thoughtful...

X2- Updates help others that have similar problems. I've seen many times where a thread is dropped without an update or resolution posted.

Thanks again for update.

[ole dollor]

thanks for the update.....now you can go and have fun with your truck....