Disc Ditching: Rebuilding Your Jeeps Drum Brakes

This ’73 Jeep had sat for years. After its first off-road outing, the rear brakes stopped working and the inside of the rear tires were covered with brake fluid. A quick inspection revealed leaking wheel cylinder seals and snapped brake shoe springs. Believe it or not, replacement hardware kits are still available at your local auto parts store for almost any Jeep model.

Running drums? Do yourself a favor and pick up an adjustment tool (top) and a pair of brake spring pliers (bottom) at your local auto parts store. Technically, you can use a screwdriver and some regular pliers to adjust and replace your bake shoes, but the right tools make the job so much easier.

Insert the end of the brake spring pliers over the retaining pin and spin to safely and easily remove the shoe springs. They’re under a fair amount of tension, so using the brake spring pliers can save you a nasty puncture wound if the spring slips and gouges into your hand.

If your wheel cylinders are in good shape and suffer only leaky seals, new replacements can be purchased at your local auto parts store for a couple of dollars. Our inspection revealed big rust chunks and severe corrosion on ours, so total cylinder replacement was our only option.

Brake lines on most old Jeeps will no doubt be rusted and weak, so if your cylinders aren’t too bad you can use a brake cylinder hone on a hand drill to resurface the inside of your cylinders. Rebuild kits that include new pistons and seals are available at most auto parts stores. That way you don’t need to try to remove the rusted brake line from the cylinder, which will almost always crumble and snap.

You can pull all your hardware off and soak it in mineral spirits to remove any accumulated grease, grime, and dirt. Scrub the adjusting hardware clean (new adjuster star wheel assemblies aren’t always available) and sand off any rust scale. By the way, a Spicer 18 oil pan makes a darn nice soaking tray.

Our local auto parts store had new shoes, brake cylinders, springs, and retaining hardware, but we had to clean and reuse our adjusting hardware. Our brake cylinders also didn’t come with new shoe pushrods, so we cleaned up our old ones, lubed the ends, and inserted them into the new cylinders before bolting them to the backing plates.

Clean, sand, and add a little grease to the shoe contact points on the backing plates so that the shoes can move freely and without sticking. We bolted on the brake cylinders and assembled the shoes with the new retaining hardware. Only do one side at a time so that you’ve got the unmolested side as a reference if you forget how things go together.

Most brake shoes will have a shorter and longer friction surface. The shorter shoe should point towards the front, or leading edge of the vehicle. If you put the larger shoe facing forward, the drums will stick when engaged and can have trouble releasing. Many of the early Jeep brake systems we pull apart are actually installed backwards, so it’s worth popping off the drums to check.

Once assembled, back the adjusting star wheel all the way in and replace the drum and mount the tire. While spinning the tire, turn the star wheel to adjust the brake shoes into contact with the drums. You’ll hear them start to make contact and grind a bit. Keep going until you get enough resistance to feel, but that the tire will still make about a half-revolution when you spin it. Each time you brake while reversing, the adjusting lever will click the star wheel one tooth to keep the pads in contact with the drums, so make sure your star wheel is in good shape and the teeth aren’t too worn. Rust-belt users should slap some antiseize on threads of the adjuster mechanism.

If you’re also doing a master cylinder replacement, blow compressed air through the lines to flush all the old, contaminated fluid out. Do it before you mount your new wheel cylinders. Bench-bleed the new master to get any air bubbles out of its internal passages. In the old days you’d bend up a couple short lines so the fluid would go back into the master, but most replacement master cylinders now come with plastic caps for bench-bleeding. No fluid can come out of the ports, but the bubbles are free to purge when the piston is stroked.

Lube the master cylinder pushrod, bolt on the new master, and connect your lines. When you bleed the system, start from the wheel farthest away from the master. On a standard left-hand-drive vehicle you’d first bleed the passenger-side rear, then driver-side rear, passenger-side front, and driver-side front. Take it for a quick test drive to seat in the new brake shoes, then jack the tires off the ground and adjust the shoes one more time. You’ll be surprised at the stopping power of a nicely restored 10- or 11-inch drum brake system.