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rear brake problem

bing

Donation Time
Greetings Earthlings,
The right rear self adjusting brake freezes up. You could say it is over adjusting. Gets hot and smokes. This has happened twice. Any thoughts on what might cause this?
 

DanR

Diamond Level Sponsor
Bing, While I do not have an answer to the cause, to disconnect the auto adjuster if possible, may eliminate the problem.

DanR

P.S. Check for it returning to the correct position after braking or utilizing the park brake.

Maybe some lubricate?
 

hartmandm

Moderator
Diamond Level Sponsor
The auto adjuster makes very minor adjustments as the shoes wear. It only adjusts when using the handbrake. Most likely, the auto adjuster won't actually adjust to account for shoe wear.

The WSM provides details about the drum brake operation and what to watch out for. It details the wheel cylinder expands and one shoe makes contact. Then as the wheel cylinder continues to expand, the other shoe makes contact. Once hydraulic pressure is removed, the return springs retract the wheel cylinder. But the wheel cylinder and shoes need to move easily against the mounting plate to allow the wheel cylinder to retract and to centralize itself. Otherwise, the wheel cylinder won't retract, or centralize, and a shoe can remain in contact with the drum.

Pull the drum and check if the shoes & wheel cylinder move freely. The shoes have lubrication points where they contact the plate. The wheel cylinder should be lubricated where it contacts the plate. Also lubricate the U-shaped retaining clip on the backside of the plate. Verify the U-shaped retaining clips for the wheel cylinder are mounted according to the WSM.

Mike
 

beamdream

Gold Level Sponsor
I have found that over the years, with infrequent use, the cylinders tend to corrode and the internal seals stick in one position usually causing the brake to remain on.

Quickest way to determine a particular cylinder fault is to crack the bleed nipple, let a little fluid out and see if the wheel frees up.
 

mikephillips

Donation Time
The auto adjusting rears tend to have, even with use, the adjusters seize up. So check those along with everything else. Also make sure the wheel cylinder can move a bit side to side as it should for self centering of the shoes as they wear and adjust out. Sunbeam didn't use the self adjusting very long, going back to manual adjusting during series V production, probably due to the problems noted above.

Also, these seem to be the same as the MGC rears, so just another source of potential parts to search for.
 

PETER CLAYTON

Donation Time
Bing,are you sure it's the adjusted that's the problem? It could possibly be the flexi hose is collapsing internally acting like a one way valve and not letting the fluid return to the master cylinder. To test, pump the brakes hard, (may be easier if you have an assistant to do this) and with the pedal released, test for residual pressure by cracking the bleed nipple open. If the fluid shoots out under pressure the hose is the usual culprit. Replace to cure.
 

RootesRooter

Donation Time
Worn brake return springs can make the rears feel like they've frozen up. Do your brakes feel permanently locked up or do they unbind shortly after coming to a halt and a few pumps of the pedal?
 

bing

Donation Time
The right rear stays locked up. I received new springs, cylinders and a hose and will have it fixed next week if I don't get stuck with jury duty, ugh.
 

bing

Donation Time
I wanted to let all of you contributors know the cause of the problem and the fix. It was a hyperactive adjuster on steroids. Replaced all the brake parts and disabled the adjuster.
 

JSLoeffl

Gold Level Sponsor
Question for "bing" or others. I see in your old post from July 2017 you had to disable the self adjuster on the RH rear brake on your Series V as it was hyper and was over adjusting the brake. Were you ever able to determine why it was self adjusting itself too tight, or are you still running with it disabled? I recently got my Series V running again after sitting in the shed since 1988. Went through all the brakes and replaced most items that were bad from sitting (hoses, hydraulic cylinders, etc.). I now have the same problem you had. My RH rear brake self adjusts itself too tight and drags. I have taken it apart a couple times now and have had to loosen up the adjustment so the brakes don't drag and get hot. But after driving it for awhile it self adjusts itself too tight again. It is only the RH side that is adjusting itself too tight, the LH side is working fine. Note: I did not replace the brake shoe return springs. Is it possible the springs are too weak to fully collapse the shoes when the brakes are released that the self adjuster tries to make up for the additional distance when I use the parking brake, hence eventually over tightening the brake??? All comments are welcome as I would like to locate the problem, rather than just disabling the self adjuster.
 

rixter

Gold Level Sponsor
I have the early series V self-adjusting brakes and have not had an issue as yet (knock on wood). I did read of potential issues that had them discarding these in favor of the non-self-adjusting type in later series V models. So when I saw a tip in the Alpine Guide related to self-adjusting brakes, I mentally noted it in case I ran into issues. I offer that up in the photo shot below for forum discussion as I've not heard of this anywhere else and am not sure of it's effectiveness.

Rick

self adjust brake.jpg
 

hartmandm

Moderator
Diamond Level Sponsor
A weak return spring could be a candidate.

The WSM mentions the wheel cylinder and shoes need to be able to move fairly easily against the backing plate. I think if the wheel cylinder and shoes do not move easily that can result in a shoe being in contact with the drum when the brakes are not applied. I ended up re-using the original shoe retaining springs, since they were shorter than the new springs and applied less force on the brake shoes against the backing plate.

Mike

upload_2021-3-8_16-51-32.png
 

JSLoeffl

Gold Level Sponsor
Mike
Thanks for that information. I did replace the brake shoe retention pins and springs with new ones from Classic Sunbeam. I will check to see if I kept the old ones in my junk pile. If my memory serves me, I do believe the new ones were longer as shown in your picture. If I find the old ones, I will compare them, and if indeed shorter I will re-install the old ones as you did to see if this helps. Thanks again for the response.

Joey
 

Mike Broome

Silver Level Sponsor
My August 1967 built S5 has the self adjust brakes and having been caught out twice by a locking left rear wheel, I bent the adjuster arm away from the adjusting cog. Easy to do and no further locked wheels.
 

Shannon Boal

Platinum Level Sponsor
My Alpine V just did this at the SUNI VII in Mo......could not figure it out until the rear hose started leaking. The driver's side (left) wheel would get hot and drag, loosening the bleeder would free it. That hose went fifty-plus years, but it failed....

Bing,are you sure it's the adjusted that's the problem? It could possibly be the flexi hose is collapsing internally acting like a one way valve and not letting the fluid return to the master cylinder. To test, pump the brakes hard, (may be easier if you have an assistant to do this) and with the pedal released, test for residual pressure by cracking the bleed nipple open. If the fluid shoots out under pressure the hose is the usual culprit. Replace to cure.
 
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