The Stovebolt Site Forums The Shop Area Driveline Rear Brake Issue '52 1/2 ton Chevy

Here's my problem/question.
We've rebuilt the brakes on my Dad's truck, 1952 3100 Chevy. The fronts work fine. The rear brakes seemed to be dragging.
We adjusted them down, removed drums and found this in the pic. Both sides looked like this.
The actuator pins coming out of the cylinders were pointing upwards and the shoes didn't appear to retract properly.
Same master cylinder as before with no issues. There was no tension on E-Brake cables as they were next to adjust.

New Napa wheel cylinders and 1 3/4" wide shoes with short shoe forward. 11" drum inner diameter. What am I missing???

Looks like the wheel cylinder has overextended. Possibly the adjusters were way too loose when the brakes were first applied. The wheel cylinders should be compressed (and checked that they don't leak), the shoes repositioned on the anchor pin and the adjuster extended so the drum barely slips over the shoes. It's possible that the retracting springs should be replaced also, but that doesn't seem to be the problem. What is the actual measurement of the drum diameter? If they've been turned too much that might be contributing to the problem.

I agree with Khansen. The wheel cylinder pistons do not seem to be retracting.

I’m not seeing the star adjuster or the spring on the bottom. I’m assuming the axle is blocking it in the picture.

Here’s a picture of mine, also a ‘51 3100. I’m not saying that this is your problem, but one thing I had some problems with installing the shoes, was the shoe retainer on the shoe anchor. The retainer slides over the shoe anchor and sits on a shoulder. When I tried to install the shoe return springs over the anchor, the retainer would slide off the shoulder. You can still install both springs but the retainer is not preventing the shoes from sliding toward the drum and opens up a gap large enough that might allow the condition you are finding.

I've removed the wheels cylinders and checked them. All good inside. No leaks. Both adjusters we're set for slight drag before test drive. I have considered the springs are just old and not doing there job anymore. May replace hardware anyway. Don't know actual drum diameter, but seem to have enough meat left to be safe. Thanks.

Yes, Adjuster was appropriate before test drive. I understand what you're saying about the shoulder. Have had trouble with that in past also. I now look from top down to make sure retainer is flush against anchor seat. I am looking for 2 new hardware kits. It appears in your picture, you have recently replaced yours? Where did they come from? PM me if necessary. Thanks.

For some reason your parking brake rod isn't engaging with your front shoe---and it has to do that for anything to work. Get a piece of wood and a hammer, put the wood on top of the shoes and gently knock them downward so they fit correctly on the top and while doing that try to catch that brake rod in the cutout piece that engages the front shoe. Your pins will self-align. If this doesn't work for you, you'll need to remove the front shoe spring and shoe and re-install so that it catches that parking brake rod like you see in Phil's picture. I'm not certain what you did to get this, but if you get the rod and shoe connected right, you ought to be in tall cotton.

The part in the yellow circle needs to slide over and fit about as far as the white arrow is pointing.

I can readjust the shoes to sit correctly on the anchor bolt with the parking brake lever positioned as you say. Then if I press brake pedal again, with or without the drums on, the shoes and cylinder actuator rods end up in basically the same shape again. Done this several times already. It seems that the return springs are strong enough as they're pulling the shoes back up towards the anchor bolt. It's as if the fluid is not allowed to return to the Master cylinder and that's what's causing the actuator rods to deflect upwards as in my picture. The return springs seems to be working against the wheel cylinder pressure? Master Cylinder was good before we tore down rear end...

The top of the shoes have a semi-circular part that fits around the anchor bolt. There's a possibility either the shoes are worn or the anchor bolt is worn. Normally, the shoes wouldn't ride up over the anchor bolt. I would check the shoes to be sure they aren't worn or the anchor bolt isn't worn. See the attached pic

The springs may actually be too weak, because they should pull the shoes back toward the anchor bolt after they've been expanded by the wheel cylinder.

Most online venders carry them. I got mine from Chevs from the Fortys. Here is some links.

https://www.chevsofthe40s.com/detai...urn_and_Adjusting_Springs_Passenger.html

https://www.chevsofthe40s.com/detai...old_Down_Kit_For_2_Wheels_16_Pieces.html

You should never press the brake petal without the drums on as that will pop the wheel cylinder pistons out.

Once you get the shoes seated on the anchor pin and all the springs shoe retainers on, put the drum on and run that adjuster out until you get a drag on you drum. At this point follow the instructions under “Major Adjustment”adjustment found in the 54 Chevrolet shop manual. The ‘54 is the same as our ‘52.This involves adjusting the shoe anchor in addition to the shoe adjustment. I’ve linked that section if you don’t already have it.

http://chevy.oldcarmanualproject.com/shop/1954truck/54ctsm0513.html

In the picture the shoes at the top look like they go around the backing plate at the top were as on phaks picture they go around the pin at the top .It could be the picture but it doesn’t look right .

As for something preventing brake fluid from returning, it is a slim possibility that you need to replace the flex line going from frame to the differential. These can deteriorate from inside out and I suppose it is possible a breakdown in that line or somewhere else in the rear line is preventing the forward/backward flow of brake fluid. There is only one line going from up front to the rear axle and only one flex tube in the rear and it would affect both sides of the axle. But that is sort of a long shot. As mentioned above, don't press the pedal until the drums are back on and the shoes are reasonably adjusted. If you have the proper shoes and you've installed them correctly, adjusted them and the anchor pins aren't just flat out ruined (another pretty slim possibility in my experience), your shoes shouldn't be able to do this...that is to say there should not be enough room in there to allow movement like this.

My shoes are relatively new but I will inspect anchor bolt to be sure it's still serviceable. Thanks.

Phak 1, Thanks for the links on hardware kits. That's what I'm looking for.
I'm also going to bleed the system thoroughly per the Shop Manual and your link and see where that leads me.

KEVINSKI, Yes, the pic doesn't exactly do situation justice. I have repositioned shoes several times around anchor pin and they do the same thing again.

Jon G, Our flex line was DEAD and we did replace it. As well, we had to replace the steel line from the divider block around the battery box back to that flex line down to the axle.

ALL, considering how much of the system we've worked or replaced, is it possible there's just still some air in the lines or in the Master Cylinder somewhere causing this issue???

Thanks to all for the help and suggestions.

I don't think air in the fluid would cause that. It's something mechanical at the wheels.

BTW, GM used the same brakes on 1/2 tons from 1951 up thru about 1972, so should hardware kits and other parts should be readily available at your FLAPS.

Like Phil said, In the service manual, it says under brake shoe replacement:

11. Centralize brake shoes and set anchor pin, then adjust all brakes and cables.....

The instructions for setting the anchor pin are in items 17 thru 19 on page 5-12 of the 48-51 service manual.

Its possible the master cyl. pushrod is out of adjustment & not letting the piston come back all the way to relieve the pressure.
Also if the emergency brake cable is stuck or out of adjustment.
Have you compaired the new shoes to the old ones? There might be a difference. Some used a different type of pushrods from the wheel cyls.
Try opening the bleeder valve & see if you can't push the shoes back in.

By any chance did you change the drums or have them cut recently?

Can you give us a picture of the adjuster?

Your profile says you live in the "South". are you close to Boiling Springs, SOUTH carolina? if so I'd be willing to come take a look. My 52 panel has the same brakes.

Looking at that photo again I don't think you have the right wheel cyl. Those old ones used external boots. The long push rods don't match The cyl.
George

Phak1 your photo shows you have the primary & secondary shoes reversed.

The push rods look OK, but the wheel cylinder is definitely funky looking. Not like the ones shown in the service manual with external boots.

I was hoping nobody would notice that! I know the primary goes toward the front. Hey, I got 3 out of 4 right! Senior moment! LOL!!!

The funny part about this was I noticed that the shoes on the OP’s picture were different that mine and I started to type a post and decided to look at more pictures to make sure I was right. After reviewing the pictures I knew that mine were wrong. I have a vague memory about noticing that and fixing it just before I buttoned it up but I’ll have pull the drum to be sure.

If you look at my picture, I have the same wheel cylinder, and they work.

It's gotta be the anchor pin adjustment then.

Since we changed only the wheel cylinders during this round of maintenance, it stands to reason we might have to adjust anchor pin. I never consider that before. Will definitely give it a go!

The master cylinder worked before maintenance so I've sorta ruled that out for now. Also, E=Brake cable are free and slack. They were next for adjustment when we discovered this problem.
I can open bleeder screw and shoes will return to normal, ie snug around the anchor pin. As per a suggestion here, I'm going to check wheel cylinder pushrods are appropriate length.
Thanks.

Drums haven't been cut recently. Adjusters are correct, clean and freely moving.
Thanks.

Thanks for the offer, but I'm in the central Arkansas "South" area.
I'd love to see your panel truck though, so would my Pop.
Thanks.

Wheel cylinders are from NAPA, of course made overseas now, but correct as of 2 days ago per a phone call. The old cylinders have external boots, but newer "replacements" seem to have the internal boot.
I am intrigued by your idea of the pushrods being incorrect. But, since these are replacement wheel cylinders, not an unusual item to replace, wouldn't you think all other OEM parts would work with replacement wheel cylinders?
Thanks.

I'm gonna try this tomorrow and see if that helps. Headed for a camping trip this weekend, so won't get much done till Monday though.
Thanks.

If it all looks normal & the brake drum will go on after you open the bleeder screw, & as long as no one has pushed on the brakes with the drum off, You have something building up pressure. If you haven't serviced the master cyl. recently now would be a good time to do it. It is easy to hone it out & put a kit in it. Most of the time you do not need a new one.
George

Quick update: It looks like the combination of new rear brake hardware and a Master Cylinder rebuilt kit from NAPA has fixed our issue. I'm not sure which one did the trick, but by the look of the brown MUD we found in the guts of the Master Cylinder, I'd say that was probably it. Since we were there, I replaced bushings on the clutch/brake pedals and readjusted pedal clearances. As always, there's never a good place to stop on these old rigs. But I got to spend a few more mornings with my Pop, so it was worth it for sure.

Thanks to all who brainstormed and threw out ideas. It's nice to have this knowledge base and all the experience right there for the asking.

Glad to hear and thanks for the update!

I agree and have tapped into this knowledge base many times!