Rear Brake Problems

[c10seth]

Hello,

Long time lurker with a problem.

'71 C/10 2WD SWB
Power brakes
Power steering

She is having some rear brake issues. All the bias, it seems, is going to the rear and locks up the wheels when I brake. There is a loud, ominous noise from the rear drums when I brake and when I remove the drums, hot to the touch, the shoes are actually blistered. I've never seen this before. I've replaced the rear brake cylinders and the mater cylinder thinking that was my problem, but it persists. Any help would be greatly appreciated. Thank you for your time.

Kindest Regards,

Seth

here she is

[RexDodge]

Knee jerk reaction is that they are adjusted too tight (rubbing/friction all the time while driving). That could be from adjusting the shoes out too far or having the e brake cable too tight. Do you have any pictures? Sounds like you have had them off so I am sure you have eliminated a leaky seal.

[c10seth]

Originally Posted by RexDodge

Knee jerk reaction is that they are adjusted too tight (rubbing/friction all the time while driving). That could be from adjusting the shoes out too far or having the e brake cable too tight. Do you have any pictures? Sounds like you have had them off so I am sure you have eliminated a leaky seal.

I don't believe they are adjust too tight because there is no noise when I'm "just driving along" and the drum is very easy to removing when I have the wheels off. The parking brake hasn't work in 20 some-odd years either lol. I believe I have eliminated any leaks; as there is no brake fluid on the floor and there is always the same amount in the master cylinder. I will take some photos when I get home from work tonight. Thanks for the help!

Seth

[Tinkermc]

I would look at the prop valve, sounds like it could all be going to the rear

[c10seth]

Originally Posted by Tinkermc

I would look at the prop valve, sounds like it could all be going to the rear

The proportioning valve is the block with the one (1) wire attachment next the the master cylinder, right? When I installed the new master cylinder last week I bled all the brakes and the fluid at the front calipers flowed very well (a little dirty with some sediment). Can the proportioning valve be adjusted? I'll take photos of everything when I get home tonight. Thanks again!

Seth

[ChevLoRay]

Have you replaced the rubber lines on the rear brake system? If not, and they are the OEM pieces, they may have deteriorated and just won't let the rear brakes work properly.

The proportioning valve seems suspect, too.

[slikside]

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[custom1970]

Originally Posted by ChevLoRay

Have you replaced the rubber lines on the rear brake system? If not, and they are the OEM pieces, they may have deteriorated and just won't let the rear brakes work properly.

The proportioning valve seems suspect, too.

X2, the rubber lines swell over time and will let pressure in but not out, there by, causing the brakes to drag or not release.

[GuyO]

Nice truck. Because the rears are working we know they are getting fluid and you say they are not adjusted too tight. Logically it would be the proportioning valve. Keep in mind the end of the valve piston (looks like a rubber button cover) must be clamped and held in while bleeding. If not the brakes wont bleed correctly, making for disproportionate pressures. Good luck! G.

[c10seth]

Originally Posted by GuyO

Nice truck. Because the rears are working we know they are getting fluid and you say they are not adjusted too tight. Logically it would be the proportioning valve. Keep in mind the end of the valve piston (looks like a rubber button cover) must be clamped and held in while bleeding. If not the brakes wont bleed correctly, making for disproportionate pressures. Good luck! G.

"must be clamped and held in while bleeding". Ah, this I have never done before...that might help. I will do this as soon as I can...right after getting the house unpacked, finishing the motorcycle and changing all the fluids on the Subie. LOL. Photos are below as promised. I did not have a chance to pull the rear wheels last night to take photos of the drum mechanics. Thank you!

Seth

[c10seth]

Hey all,

I haven't had a chance to re-bleed the brakes yet. I had to put the bike back together after getting the forks refreshed and had to change the oil and front brakes on the better half's car. Hard life, right? . I'll be out of town for the next week, so she's going to have to wait a little longer. Thanks again.

Seth

[cdowns]

when u replaced the master cylinder did you make sure the actuating push rod for it was within spec of what is called for in the factory service manual

[c10seth]

Originally Posted by cdowns

when u replaced the master cylinder did you make sure the actuating push rod for it was within spec of what is called for in the factory service manual

Nope. I bought one from Autozone, bench bled it, installed it, and bled the brakes. I have an assembly manual, but would an Autozone master cylinder specified for this year truck be so far out of spec that it it would cause this problem? And when you say, "within spec" what measurement is that? Thanks for the input. I never thought that would be an issue.

Seth

[c10seth]

Ok,

Made some progress tonight. Now, when I took the prop. valve off I blew compressed air through it and and the small valve on the end actuated out. Is that how it's suppose to work? (assuming it's brake fluid and not air). Also, I have no clue why photobucket won't save my edited photos, so sorry about sideways photos.

[GuyO]

Hey, that is progress. The fact the centering valve moved is a good sign, it means it isn't stuck. Once you get it back together CDowns knows his stuff. If the push rod is the right length and it pumps like it is supposed to, with the brakes properly bled (prop valve button held in, then drivers rear, passenger rear, passenger front, drivers front with the bleeders higher then the hoses) and the prop valve centered the only thing left would be wrong installation or wrong parts in the rear drums. I have done rear brakes many times, they are simple; wheel cylinder, springs and caps, seperation bar, adjuster. BTW the bolt looks bad in the end of the prop valve but is being used as a threaded plug. You can get a prettier plug in any hardware store with a decent bolt/nut/stud/fastener collection. Keep us posted! G.

[c10seth]

Thanks for the reply, GuyO. I didn't write much because I was beat when I got back in last night. The bolt confused me once I saw the diagram for the prop. valve in the shop manual because two (2) line are suppose to go to the front brakes; not one.

I was also confused because the shop manual called out a different brake setup than what is actually on the truck (for a C10). Given the manual is a '72 and my truck is a '71 could be a difference?

I have bought new brake shoes and I will get the drums turned to be safe. I will re-assemble everything and see how it goes. Thank you.

Seth

[c10seth]

Ok. I think I figured the problem out. And I feel like an epic dumb*** if this is the problem. The brake plate that braces between the shoes with the springs on each end is missing from both drums. How the funky-wacos does that happen? None of the auto part stores around can get these, so I'll have to resort to online. If anyone knows where I can get a pair please let me know. I'll start with LMC. Thanks.

Seth

[LEEVON]

That'll do it! I hate brake gremlins.

[Daddy Brim]

Win I bought mine it was missing the parts for the self adjusters. Drove it for a year before I found out. I would try local parts stores first. They had all the parts I needed.

[c10seth]

Hey all,

So, I talked with a pretty knowledgeable guy at one of my local auto parts stores and he very confidently informed me that the brake strut bar and spring on each side is only for the parking brake...which hasn't work in 20 years. As we talked about it we dwindled my dilemma down to two options;

1) Either my ar-tard self put the brake shoes on backwards since one is short and one is long.

OOORRRRRR

2) the rear, rubber brake line is swelling on the inside. However, with this I can't believe it would be giving me the chatter, heat and noise I was getting at it's worst.

I purchased new shoes and had the drums turned and I will put this all together tonight. I would have done this all sooner, but it has been hotter than hell here for the last week. Thank you.

Seth

[c10seth]

IT'S FIXED!

The new wheel cylinder I bought was bad, so got another one, had the drums turned, bought new shoes, fitted a new section of brake line to the LR, the valve on proportioning block doesn't need to be closed when bleeding, and that strut bar had nothing to do with it.

Brakes feel so good and safely stop me. Yaaaaaay! ^_^

Seth