Rear Drum Wheel Cylinder..both went out?

[Neu]

So I thought I had a bad master cylinder, but finally the brakes actually gave completely out. I was in the woods, and managed to drive home just fine by downshifting and shutting the engine off to stop.

So I went to fix what the problem was, turns out the wheel cylinder/piston in the back is bad on BOTH sides. Fluid just shoots out of them both, oddly enough neither of them shoots fluid from the same spot.

They are 11 dollars for me, each, so it's not a big deal.

Any idea why both went out at the same time? I"m assuming they weren't adjusted very well, and that caused it.

[Petros]

I would guess they were the same age and both were marginal, and then a sudden panic stop, or even a hard bump perhaps during normal breaking, caused them both to blow out.

Usually if one is bad, the the other is "almost" as bad. IOW, bad leak on one side (that caused you to inspect them) and you find minor leak on other. So it would be just a matter of time for that one too, you just got "unlucky" that both went at the same time.

[keith]

The design used by Japanese carmakers for rear drum brakes is not very good, the American design is a lot better. In the American design, the wheel cylinder is at the top of the backing plate and the star wheel is at the bottom, at the hinge point. In the Japanese design, the star wheel is just under the wheel cylinder.

In the American design, as the shoes wear down and the drum wears outward, the self adjusters expand outwards making the tops of the shoes push the pistons back toward the center of the wheel cylinders. In the japanese design, the self adjusters push the shoes further apart at the top, causing the pistons in the wheel cylinders to push outward. If the shoes and drums wear enough, the pistons can pop out and result in a sudden loss of brake pressure. I've seen it happen. 84 Honda Civic Wagon. Dual master cylinder didn't help, as soon as one piston popped out, the pedal went to the floor and no brakes, even though the other side hadn't leaked yet.

[Neu]

that sounds like exactly what happened, maybe i'll do the pads too, they were getting a lil bad.