Leaking brake fluid from the rear

I liked the idea of @Littles "trail repair" with a minimum of parts storage space. If the failure occurred in town, yes replace the whole cylinder. I will study the ease of replacement of an O-ring versus the very easy replacement of the cylinder.

 

These things are pretty stout, however I think you have a pretty good idea, I may have to do that myself.

 

So I've taken it apart and it looks like I blew a seal? I took a close-up, any ideas what the stuff is poking out?

 

Nothing is poking out. You are seeing the dust boot pulled off of the cylinder housing cause the piston over extended on the one side.

 

I don't really see anything. Was that dust cover like that when you opened it up?

That rubber boot is just a dust seal for the piston. It doesn't look wet. It doesn't hold brake fluid in. Inside the cylinder, on each side has its own small piston, with an o-ring. That seals against the cylinder as the brake pressure comes from the hydro fluid in the middle. That oring inside the cylinder is what holds your break pressure. Not the dust cover.

 

If you look at the slave cylinder, there's the Spring pushing against two black rings. Those are the o-rings that I suspect failed. The lighter gray on the left and right of the dark o rings would be your dust covers.

If for some reason one side or the other blew past the end of the cylinder, you'd have a leak. If the o ring doesn't break whenn it settles back in, that might explain why the dust cover is popped but it doesn't appear to be leaking.

If it were my truck, I'd replace this wheel cylinder, and shoes on both sides unless you pull the other side apart and suspect fuckery. I'd take a close look at those turn buckles that are supposed to auto adjust your rear brakes and makes sure they aren't seized up. I think they only impact the parking brake, but while you're in there make sure it's all lubed and turning correctly.

I know this has been said before but, DO ONE SIDE AT A TIME. Those springs behind the hub are a pain if you haven't done shoes before. After a few times you just know you're gonna curse a lot and smash your knuckles, but you get better at it.

 

Ok, that makes a lot of sense. I forgot to mention, those pictures are after I cleaned it off and took a good look at it. Here's what it looked like right after I pulled off the drum.

 

OK that helps seeing it before the cleanup. You were holding out on us. Theres a lot more wetness and evidence of a slow bleed in that Pic than the first. I would guess one of the seals is failing.

Replace the cylinder on this side without a doubt. Shoes on both. Make sure your adjusters are working properly when it all goes back together. Like I said, never hurts to have a spare rear wheel cylinder in the parts tote. They are cheap and take up little space. Oh also a big bottle of brake fluid.