Rear brakes real hot

[ESP47]

This is a 68 Barracuda with an 8 3/4 that I picked up about 10 years ago. Looks to be a stick A body housing. No idea on the year. It has Mark Williams axles and green bearings. I also rebuilt the center section and changed the ring and pinion plus all the bearings.

I'm shaking the car down after rebuilding most of it and I can smell the rear brakes when driving. I got it back home after a 2-3 mile jaunt and used a laser thermometer on the rear drums and got readings as high as 500* on the drums themselves. 110* on the axle housing and for whatever reason I forgot to take a reading of the center section.

Rear drums measure 10". Shoes measure 2.5". Drum shoe surface roughly 2.75".

I loosened up the rear drums adjustment farther than what id normally run and I readjusted the parking brake. I can turn the wheels by hand with the car jacked up.

Took it back out and I'm getting the exact same issue. Any ideas on what I'm missing here?

 

[Darter6]

Disconnect the left and right brake cables at the clip from the front cable(s).
Had the same with mine and it was the cables needed cleaned and lubed.
They moved but not enough to release completely.
Also check the spreader bar(s) for the park brake. I had a car that had the wrong size.Too long.
My 2 cents.

 

[Murray]

If needed, the rear e-brake cables can be removed, cleaned up and lubed.

 

[MDchanic]

Yes, you can have an emergency brake that appears to function (gets tight when pulled, loosens up when released), but both cables are darned near completely seized.

Happened to me. Very frustrating, because I KNEW the cables were free.

As soon as I disconnected the cables and pulled on the ends with a pair of Vise-Grips, I was shocked by exactly how much they didn't move.

It's usually best to just replace the cables. Sometimes they can be loosened up, and sometimes they can't. Replacements are cheap.

Also, note that you can't effectively adjust the emergency brake with the car on the lift, as the wire runs below the driveshaft, and if the rear wheels are hanging, the driveshaft will also place some tension on the emergency brake cable, messing up your adjustment.

– Eric

 

[jrc4y4]

I ruined my rear brakes because my e brake cables were hanging. Would act released but would tighten up while I went down the highway. Used it as an opportunity to swap to an 8.25 from 7.25 though lol. Happened on a road trip. Removed the brakes and put vise grips on the brake line and made it the last 100 miles on just front brakes. I’d replace the cables if that’s what is going on with yours. Good luck!

 

[AJ/FormS]

You got any up and down play on those axles?

Maybe check that your compensating ports are open, at the bottom of the Master cylinder..

 

[Dana67Dart]

I'm assuming automatic.


Get the rear safely on jack stands. Start the engine and with you foot on the brake put the car in drive.

Take you foot off the brake and give it some gas till it's in 3rd gear.

Let it run at about 60 for a minute or so then put on the brake till they stop. Do this a number of times.

Then let it spin far a few minutes and check the drum temp, the center of the axle temp and the temp under the pinion.

A fresh center section will get hot till it breaks in.

I put a temp probe on my center and kept the temp under 200 f or so.

I also had brakes issues, but I tracked mine down to over turned drums 10.100 ( just a number for illustration) and 10.000 shoes. Only a small portion of the shoe is touching the drum. I put the used shoes back on and the issue went away.

What I did was drive for a mile or so and found a place where I could come to a stop with little or no brake application (slight incline) then I measured the drums in each side and the center of the axle and compared left to right. Once they were both running the same temp and not heating up just running I figured I had found the sweet spot for adjustment.

Side note: be sure your adjusters are on the correct side or every time you apply the brake they will tighten.

 

[ESP47]

Thanks for the replies guys. I haven't been able to mess with the car until today.

I'm 99% sure my star wheel adjusting screw is too long. I looked in a box of old parts and I have another star wheel in there that is shorter than the ones that are on the car currently. Does anyone know if there's supposed to be different lengths between the years or if it's dependent on brake shoe width?

 

[Dana67Dart]

You have 69 and up brake hardware. Spring in the adjuster cable.

The adjuster pulls up to make the adjuster lengthen.

68 and down pushes down on the adjuster.

Be sure you have the correct adjuster for the hardware

 

[ESP47]

You have 69 and up brake hardware. Spring in the adjuster cable.

The adjuster pulls up to make the adjuster lengthen.

68 and down pushes down on the adjuster.

Be sure you have the correct adjuster for the hardware

The adjuster I'm using came with the hardware.

I'm just not sure if I have the wrong mix of parts or what. I don't know what year vehicle this 8 3/4 came out of or what type of backing plates are on it. I have 10" shoes that are 2.5" wide. They might be 68 shoes. Hardware is 69+ like you said.

I have the adjuster screwed all the way in and the parking brake cable disconnected and I can't even get the drum to go back on over the shoes. Nothing looks out of the ordinary. No weird wear patterns of anything like that. Parking brake cable moves freely but I figured I'd disconnect it just to rule that out completely.

 

[Dana67Dart]

Are the top of the shoes touching the center post?

69 up adjuster all the way in

If the shoes are 2.5 then you have BBP B,C,E body backing plates. If your drums are A body SBP there is a problem there.

Or if you have 10x1.75 A body Backing plates and 2.5" shoes that's a problem.


A body 10x1.75 backing plates will be about 0.56" from the ruler to the seat the shoe rides on.

 

[ESP47]

Are the top of the shoes touching the center post?

69 up adjuster all the way in

View attachment 1716402544

If the shoes are 2.5 then you have BBP B,C,E body backing plates. If your drums are A body SBP there is a problem there.

Or if you have 10x1.75 A body Backing plates and 2.5" shoes that's a problem.


A body 10x1.75 backing plates will be about 0.56" from the ruler to the seat the shoe rides on.View attachment 1716402551

Thanks for the pics and your time. I appreciate it.

They're touching the center post if I slap them inward but they might hang off them 1/8" of an inch or so.

I measured my adjuster wheel and I'm getting the same measurement as you.

I don't know if brake shoes are measured in a literal sense but mine are 2.42" wide on the caliper.

I also don't know if there's an official way to measure the drum contact area itself but from the outer lip of the shoe contact area to the inner part of the drum is 2.88" on the caliper. That is the flat contact area in total.

The backing plate measurement I'll have to try tomorrow if I can even get an accurate look at it since the axles are in. The rear has aftermarket BBP Mark Williams axles and the drums aren't redrilled.

 

[ESP47]

I found some 2" shoes and put them on and I still have the same issue. Searching on here, I also completely forgot that I posted a thread a couple years back where I was dealing with a very similar issue with a different 8 1/4" rear end on this same car. I wound up swapping that to the 8 3/4" before I ever got the chance to drive the car.

My "fix" in that thread was cracking the bleeder and pushing the shoes in until they made perfect contact with the center post. Well it doesn't look like that's really a fix because the same thing is happening again with this rear end. It seems as if the evidence is pointing to a hydraulic issue rather than a hardware issue.

@67Dart273 said "Make CERTAIN your master is properly returning and relieving at the ports (bottom of the reservoir)".

Can you give me some more info on that? Other than pulling on the brake pedal to see if there's more travel left in it, I'm not sure how to go about troubleshooting that in a more professional manner.

 

[Dana67Dart]

Do you have power brakes?

The rod is adjustable and should not be longer then the depth into the master.

 

[mopar head]

Maybe the flex hose has collapsed and not letting fluid return.

 

[ESP47]

Do you have power brakes?

The rod is adjustable and should not be longer then the depth into the master.

It has manual brakes. "New" master cylinder and I rebuilt an original prop valve.

Maybe the flex hose has collapsed and not letting fluid return.

I'll give it a once over this weekend but it's a brand new hose with about 15 miles on it.

 

[Inertia]

Not the problem, but the wire adjuster cable in first pic is trapped under the tin/curved wire guide, likely impairing self-adjister.

The return springs shouldn't overlap (criss-cross) at the top.
(Not the problem your looking for).

 

[nutz]

the top of the shoes should rest on the top post ,if not your p-brake is miss adjusted or p-brake cross bar is wrong /in wrong

 

[ESP47]

the top of the shoes should rest on the top post ,if not your p-brake is miss adjusted or p-brake cross bar is wrong /in wrong

Looks like I have a hydraulic problem. One shoe on both the pass and driver side of the car will sit off the top post by about 1/4". This is with the parking brake and the cross bar strut disconnected and removed.

I placed the cross strut back in, cracked the bleeder and the spring tension pulled the shoe up to the top post. Drums go on fine after that. I'll pump the brakes a bunch with the drums on and everything seems okay but as soon as I take the car out and drive it (with the parking brakes disconnected), the shoes start dragging and the rears start smoking in short order. Jack it back up, take the drums off and sure enough, one shoe on each side is 1/4" off the top post. I can jiggle the strut when this is happening so it's not causing the issue.

I bought an aluminum MC from Dr. Diff so I'm hoping that fixes it. I was going to get that anyway to give me a little more clearance with my headers so hopefully it kills two birds with one stone.

 

[nutz]

Would pump it up and Crack it at the master
Could be a brake hose

 

[67Dart273]

If something is wrong AKA wrong master/ linkage problem/ length of pushrod, the master piston may not be returning, and holding pressure in the system. Try cracking the tubing at the master, and or have someone work the pedal and be easy, slow and careful, look in the master reservoirs and see if fluid is returning through the ports in the floors of them. I say be careful, because sometimes then can spurt up, get on the paint, or even in your eye.

 

[65 Cuda 340]

If something is wrong AKA wrong master/ linkage problem/ length of pushrod, the master piston may not be returning, and holding pressure in the system. Try cracking the tubing at the master, and or have someone work the pedal and be easy, slow and careful, look in the master reservoirs and see if fluid is returning through the ports in the floors of them. I say be careful, because sometimes then can spurt up, get on the paint, or even in your eye.

Had a problem with my brakes not releasing with my 49 Dodge. Professional mechanic friend of mine suggested the port in the floor of the (single pot) M/C was clogged. Sure enough, it was. Just look for fluid coming up from the floor when you apply brakes. I had been about ready to buy a new master cylinder. He took me to a guitar shop to get guitar string. Poked that into the port and got it cleared up. Brakes fixed. Cheaper than a new master!

 

[ESP47]

Thanks guys I'll get a helper and get a visual on the fluid in the MC before I swap it out.

 

[Inertia]

If the shoes are loose enuff to come off the top pin, that indicates to me the adjusters are so loose to give them too much room to move around.

Do you have a hard pedal right at the top of travel, or do you have to pump once or more to get resistance from the pedal ?

The adjusters prob should be a dozen turns or more out from screwed in, - when put together with the shoes on the top pin.

Try putting it together with shoes on top pin. Keep slipping drum on, if it goes on easy, lengthen adjuster, slip drum on, - repeat, - with shoes on top pin till drum won't slip on.

Shorten adjuster a coupla turns, slip drums on, test drive. when properly adjusted, the shoes shouldn't move more than 1/8 inch each or less, never mind shift up off the pin.

Install emergency brake hardware

Good luck

 

[RGAZ]

Is it me or does that brake have the wrong spring on the right? It appears to have two of the front springs because I thought the rear spring was shorter than the front.

Maybe I am seeing things?

RGAZ