Brake stuck (again) , wheel cylinder blew out

[MilesnMiles]

Ok, this is an odd one and I’m currently stuck. When I first got my car I notice that if I reversed a little fast there was a clunking noise somewhere at the rear end. A few days later noticed a hot rear brake drum, posted on FB about the struggle to get it off. Did eventually and found the spring for the star wheel hanging loose, fixed it and drove on.

Today whilst driving out I noticed my brake pedal was sinking too much, I managed to get back through town constantly pumping the brakes and arrived in one piece. Here’s where it gets wierd..
I checked 3 of the wheel cylinder and noticed one had a slight leak. I checked the MC and noticed a tear in the diaphragm and thought that may be the cause.
I then reversed the car down the drive and heard some nasty metallic nose from the rear, suddenly lost all pedal and stoped the car via handbrake before I crashed it
A quick check showed that the rear wheel that I’d had trouble with previously had completely blow out and there was fluid everywhere. I’m sure something is wrong with the brake parts but no idea what.
Any ideas what happened here?
Also, the drum
is stuck on and refuses to come off and I’m stuck.

[Dave999]

sounds like

1) the problem drum was out of adjustment with the shoes backed right off and the adjuster fell out of its proper position
2 reversing triggers the auto adjuster which probably didn't auto adjust, the lever just pushed the adjuster out of its position further rather than winding the star and expanding the length of the adjuster against the shoes and retracting springs
3) you got by, by applying the brake which must have wedged the adjuster and stopped the cylinder blowing out
4) the adjuster eventually fell out leaving the shoes flapping
5) pressing the peddle now allows the cylinder to fill and push the pistons right out of the cylinder causing catastrophic brake failure..

probably not that
but you ended up with flapping shoes and it allowed the brake cylinder pistons to go past their end stop and out of the cylinder.

usually an issue with badly worn shoes and drums that have been worn away to 1/2 their wall thickness.....had the same problem on a split screen VW drums were way past their sell by date with a ridge of about 2 mm out of spec..by a mile.

massive loss of fluid from the Master Cylinder, can suck the top gasket or diaphragm down so low it rips. it usually has 1 or 2 dimples in it to cater for this but they can only stretch down so far and the rubber degrades anyway

Dave

[Dave999]

drum stuck is probably caused by shoes rammed right round past the anchor pin
and a massive step or lip between the swept area and the edge. potentially not 2mm but any lip will cause this

screw driver in through any hole and try and loosen them off
wind the hub back and forth with a bit of angle iron, long lever, bolted across 2 of the studs, you need to get the shoes back into more or less the At Rest Place, you may snap the studs i have a bag if you are stuck

a BFH might be necessary

or borrow a hub puller and suffer the fact it will probably bust/bend the shoes and the puller

look up duo servo brake bendix to see the parts

[Dave999]

see if that adjuster falls out (bottom) any pressure applied by the cylinder (TOP) to the other end of the shoes just drives them round and allows the cylinder to pop

the adjuster will fall out if you wind the star around far enough to make the end caps get to the end of their thread
that auto adjust lever can do this if the shoes and drums are worn past their lowest...i.e out of specification

have you done a bit of reversing recently??

it activates and winds the star round every time you reverse and can wind the centre section out of the threads of the cap section that fits into the shoe.

i took the auto adjuster out of my charger as i was sick of getting binding rear brakes every time i reversed....
the aussies do an RT only spring set to achieve this bottom spring slightly longer so it goes shoe to shoe not front shoe to a hole in the adjuster
or i guess you could potentially use one from a 10 inch drum on a 9 inch drum or an 11 inch drum on a 10 drum

picture isn't mopar so the adjuster set up isn't quite the same in respect to spring mountings and its missing the hand brake rod/beam

[MilesnMiles]

Thanks Dave, triffic answer/explanation as usual.
In order, yes I reverse 15 yards out of my garage every time I use the car.
The catastrophic blow out occurred when reversing.
I could hear something metallic as I was pumping the brakes to get home safely literally yards from my house.
Looks like I’m into a lot of new parts and chuck the adjuster away (it’s safe to do that?)
Il try your tips on drum removal, it locked before so probably time for a new drum too.

[kma176]

I have a few second hand brake parts for my 71 B'body if you need them?

[MilesnMiles]

Thanks fo the offer, much appreciate that. I’ve already ordered a bunch of parts from Rockauto.
Dave was spot in with his diagnosis as usual. Pic shows the carnage

[Dave999]

you can run the adjuster lever fine if the shoes and drums are in nice and new or at least new like condition

and of course you need that bit with the star shaped wheel on it.......thats vital

issues start when everything is too far worn out

you can get drums for yours relatively easily

i have a a combo that isn't made in US. a 9 inch drum with the 5 on 4.5 PCD for the wheels

i guess yours will be 9 or 10 inch with the small PCD...i.e rockauto probably sells the stuff

don't worry about the distance you reverse, its application of the brakes reasonably hard when rolling backwards that triggers the adjuster.

application of handbrake might as well, discussed with blue and phil at the weekend i can't remember which shoe gets the main shove from the lever when you put on the hand brake.

dual circuit master cylinder might be a plan.......!

Dave

[MilesnMiles]

Yeh Dave, I think the first time I heard something awry was when I bought the car, fanged it into reverse quite hard when Turing round at a fuel stop and heard something ratchety, in hindsight I would say tat the adjuster was playing up. I also noted that the handbrake was mega efficient too, but may also have led to the brakes initially sticking on. Anyway, large order from Rockauto on its way currently.