Master cylinder and brake cylinder specs?

[mohammad]

Hell friends,

I am wondering if anyone can tell me the inner diameters of both the master cylinder and the brake cylinder? If possible a bore and stroke and a total brake fluid volume would be ideal. I am interested in finding out if the auto-adjuster wasn't working, say if the teeth on it were worn down, if it would be possible to brake at all? Because if the brake cylinder volume is close to the master cylinder fluid volume that it may not be possible to brake.

[Fopeano]

Short Answer: You're not going to lose your brakes.

No matter how worn that auto adjuster is, the wheel cylinder (US terminology) will never over-extend and leak out. I think that's what your asking. Even with the shoes worn all the way and metal to metal, you would have to be listening to that grinding for a long time before the pistons will come all the way out and leak brake fluid. Even if that were to happen all all brake fluid possible leaked out, you would still have the one front and rear brake working on opposite corners.

That is why there are two pipes coming out of the master cylinder. There are two separate hydraulic systems coming off the master cylinder to if there is a fluid leak happens, you still have half the braking system available. When that happens, which I've experienced many times, the brake pedal feels scary and the braking you do have throws the car off balance. If a person experiences driving like that and doesn't have it fixed, they deserve the consequences.

[mohammad]

Short Answer: You're not going to lose your brakes.

No matter how worn that auto adjuster is, the wheel cylinder (US terminology) will never over-extend and leak out. I think that's what your asking. Even with the shoes worn all the way and metal to metal, you would have to be listening to that grinding for a long time before the pistons will come all the way out and leak brake fluid. Even if that were to happen all all brake fluid possible leaked out, you would still have the one front and rear brake working on opposite corners.

That is why there are two pipes coming out of the master cylinder. There are two separate hydraulic systems coming off the master cylinder to if there is a fluid leak happens, you still have half the braking system available. When that happens, which I've experienced many times, the brake pedal feels scary and the braking you do have throws the car off balance. If a person experiences driving like that and doesn't have it fixed, they deserve the consequences.

You are correct,

I attempted to change my own brakes once and I did one side, couldn't get the drum back on then re-installed the old shoes. When doing so I forgot to install the spring that goes from the auto adjuster to the trailing shoes and i intentionally did not install the lower main spring that holds the shoes together, as i only wanted to drive a few km to go to a mechanic(photo attached). The brakes worked after the reassembly, both the service(foot) brake and the e-brake worked. After a few meters of driving, the auto adjuster fell out of place causing the complete failure of the parking brake of that one side of the car, and the brake pedal went to the ground. The other hydraulic system of the two you mentioned was working.

The mechanic says that the brake cylinder pistons were found dangling freely when he disassembled the drum as the shoes had slid down when the auto adjuster fell out of place.

My questions are as follows:
1. if i had changed shoes on both sides and forgotten the spring that connects the auto adjuster to the trailing shoe could i have caused a complete loss of all service(pedal) and emergency brakes?
2. Did me not installing the lower main spring that connects the middle of the two shoes together contribute to the cause of this failure?
3. should we not be concerned that the failure of this one spring can cause a loss of brakes?
4. Does the space even exist for a worn set of shoes to slide down off the pistons? Its possible that this could have been caused by me when I pulled all the way on the e-brake? maybe the parking brake lever pushed against the cylinder and forced the shoe downward off the piston?

[Fopeano]

1) I'm not sure, but it's possible
2)probably not
3)Even if that happens, you'd still have the brake system on the other side working before total failure.
4)I'd be surprised. Mirages that come in with the shoes metal to metal don't normally have the pistons extended outside the wheel cylinders. It has to be extreme neglect for that to happen. Even still, the shoes are a precise fit in the drums and can't fall out of place to allow the wheel cylinder to over-extend. They would have to be shattered apart for that to happen.

I'm thinking several things...

-The white spring in your picture could pull the shoes/pistons in far enough into the wheels cylinder to leak if the adjuster were not there to limit it.

-In the picture, the lever attached to the handbrake cable is way too far out. You usually have to loosen the adjustment on the handle inside the car to allow that lever to sit almost completely behind the shoe. With new shoes assembled properly, you can't get the drum on unless there is no tension from the cables.

-These brakes are not easy to do or set up properly

-We had a car a couple months ago that had rear brakes done at a Midas and paid big money. The pedal went to the floor, and my guy working on it nest to me couldn't get the new drums off to even figure out what happened. We fixed it by installing a used rear axle beam and brake assembly. We will never know how a professional screwed that up so bad that we had to scrap the whole thing. If a paid professional can ruin this brake job, you can too.

-Looking at the picture again, the white spring looks bowed like the forward shoe isn't hooked behind its retainer at 3 o'clock on the backing plate.

[Wallythacker]

-We had a car a couple months ago that had rear brakes done at a Midas and paid big money. We fixed it by installing a used rear axle beam and brake assembly.

Doesn't Midas have a lifetime warranty on brake work? For a shop to bugger it up that badly they have to take some responsibility. I hope the total hit to the owner wasn't too horrible. Did you document everything well so the owner could pursue this with Midas?

There's no way I'd be paying to have an entire axle swapped in at my cost when a big shop like Midas last touched it. No way in hel7.

[foama]

Sorry to say, but obviously something has been thoroughly goofed up.
Mohammad, take a look at the FSM!
You may want to take off the drum on the other side (dont forget to loosen the handbrake!) and take some pix before putting it back on without doing anything else.
Then with the pictures printed out and laying in front of you, have a look at the troublesome side.
"Who searcheth shall findeth" Seasons greetings

[mohammad]

Sorry to say, but obviously something has been thoroughly goofed up.
Mohammad, take a look at the FSM!
You may want to take off the drum on the other side (dont forget to loosen the handbrake!) and take some pix before putting it back on without doing anything else.
Then with the pictures printed out and laying in front of you, have a look at the troublesome side.
"Who searcheth shall findeth" Seasons greetings

This actually occurred quite a long time ago, im just trying to my best to figure out what occurred so i can make a youtube video on the topic.

[mohammad]

-Looking at the picture again, the white spring looks bowed like the forward shoe isn't hooked behind its retainer at 3 o'clock on the backing plate.

I dont think its possible to assemble the brakes without hooking the shoe behind the retainer, i recall trying and failing because the shoe would immediately bow out and fall out of place as i stretched the springs out.

My best guess as to what occurred is that without the auto-adjuster the parking brake lever pushed against the brake cylinder causing the shoe to slide down and no longer contact the piston. Then after the shoe slid down the piston slid up the sloped part at the top of the shoe directly above where it should sit causing a loss of the service/pedal brakes.

3)Even if that happens, you'd still have the brake system on the other side working before total failure.

if i had changed the brakes on both sides and made the same minor mistake since the two hydraulic loops are diagonal I could/would have potentially lost all hydraulic and emergency/parking brakes.

The white spring in your picture could pull the shoes/pistons in far enough into the wheels cylinder to leak if the adjuster were not there to limit it.

Looking at the video i shot during my failed install i did have it assembled without the adjuster in place at one point. It did not immediately start to leak. I think that by design the shoe will hit the body of the brake cylinder, otherwise during install if you are installing one shoe then trying to stretch the springs to install the other it would eject the other piston and/or leak.

[mohammad]

I went ahead and made my video based on my hypothesis on the cause of failure, if anyone has any comments feel free to leave them below the video: https://youtu.be/4A1cE_RMtsQ

[foama]

Quite a nightmare! Good that you solved the problem, albeit at 3am.
Before and during drum brake repairs or any other seldomly done complex jobs, it is always a good rule to take numerous photos! That way, if something gets goofed up, its so much easier finding out what is wrong.
A pair of small sized double-ended brake spring pliers can be helpful too. I have a regular truck-sized one, much to big for these cars.