The inside guts of a rear wheel brake cylinder... it was new to me

[1998_K1500_Sub]

I recently removed the old rear brake cylinders from a 9.5" axle junkyard find, and I figured I would push the guts out of one just to see what's inside. I've never actually looked before.

Net net: Within the cylinder housing there are two metal pistons, each with a (rubber?) piston cup. In between was a spring assembly which pushed equally against the two piston cups to force them against the pistons and outward.

Not shown, because they're normally visible w/o disassembly, are:

- the rubber end caps / retainers that are typically visible on the ends of the cylinder

- the little "pusher-thingies" that actually stick out of each end of the cylinder and engage the brake shoes w/ the pistons.

Nothing complex here... but interesting just the same.

This cylinder's bore measured 1". It was from a JB6 11" drum 9.5" six-lug axle.

 

[454cid]

Yeah, there's not much too them. I'm hoping I can rebuild the ones on my 69 Buick. I think I bought the kits already, for the front. I'll have to borrow my dad's cylinder hone that was probably last used in the 1980's on his 76 Dodge D100.

 

[1998_K1500_Sub]

I'm hoping I can rebuild the ones on my 69 Buick. I think I bought the kits already, for the front.

What's your plan for installing the (rubber?) piston cups? One cup can go in easy (shove it in from the opposite side) but the remaining cup... might be tricky or might not.

I should have tried reassembling one.

 

[454cid]

What's your plan for installing the (rubber?) piston cups? One cup can go in easy (shove it in from the opposite side) but the remaining cup... might be tricky or might not.

I should have tried reassembling one.

I haven't given it any thought. It used to be done all the time, so I figure it can't be too difficult. My biggest worry is if the cylinders are pitted, or somehow too far gone.

 

[dave s]

I can remember rebuilding plenty of those in the early 70's and 80's. I still have the little hone tool in my toolbox. Hasn't been used in years though. I just started replacing the whole assembly when needed. But as a kid, a rebuild was the way to go as they were super cheap and I didn't have a lot of money to waste. It's cool you tore it apart to check it out.

 

[Schurkey]

Rebuilt heaps of wheel cylinders years ago. There's no problem poking the rubber seals into place. Slide 'em in kinda sideways, when the seal is inside the cylinder, push it flat 'n' true in the bore. Gotta work around the spring, but once you've done it, you'll understand.

Yup, the big problem with wheel cylinders is bore pitting/bore wear. Honing helps--sometimes. Pitting won't hone-out.

The spring either has metal cones at each end that fit inside the rubber seals, (like yours) or the spring coils are wound into a taper at the ends, again to fit inside the rubber seals. This kinda-sorta pushes the seal lips into the bore. But remember, those seals are designed to keep brake fluid IN, they're not real good about keeping air OUT.

I have--mostly--quit rebuilding wheel cylinders. The rebuild kit costs about the same as a new wheel cylinder, and the new cylinder has a warranty. And, there's no fighting the rusted/seized bleeder screws.

 

[GoToGuy]

The more widely available new wheel cylinders have become, and the prices are reasonable. The less , incentive, justification, need? New is clean, paint ready, no corrosion to work off. New bleeders. A lot less time involved for a drop in install. Much less labor overall.
A while back new cylinders were expensive, rebuild kits are cheap. I could get a new " US mag wheel " for the price of two wheel cylinders.

 

[movietvet]

As in the pics you show, you can see the crud that can build up in a brake fluid system. Combination of fluid breakdown with age and heat causes this. Now you can see why brake fluid should be flushed at mileage intervals.

Last time I rebuilt wheel cylinders and calipers, was in the 80's.

 

[1998_K1500_Sub]

As in the pics you show, you can see the crud that can build up in a brake fluid system.

^^^ this

The fluid in the cylinder was simply black. There was some sort of crud on everything.

 

[movietvet]

^^^ this

The fluid in the cylinder was simply black. There was some sort of crud on everything.

That means the entire brake system fluid has contamination. Prime case for a flush and may still have components too far gone to salvage. FUBAR