Classic-car brakes, in general, are pretty simple and generally hassle-free. Most of us don’t run our cars often enough or hard enough to warrant regular replacement of the factory components — especially with regard to OEM rear drums that only handle a small portion of the actual stopping.
That leads to a hidden issue that you might not have thought of — leaky wheel cylinders. And no, they don’t need to be pouring brake fluid down your tires before you should consider replacing them.
Brakes are supposed to be a sealed hydraulic system, and that seal is most vulnerable at the wheel cylinder — mostly from moisture that seeps past the cylinder’s sealing surfaces. Over time, that moisture leads to rust that can destroy your brakes from the inside out.
When did you last replace the wheel cylinders in your muscle car? If you can’t remember, it’s time, and we’re here to show you not only why it’s important, but also how to get the job done quickly and easily despite the maze of drum-brake springs and clips in the way.
My 1966 Caprice was our subject car, but most American cars from the 1950s through the 1980s use a similar setup. We’re only focusing on the rear here, since I already converted the front of my car to disc brakes — but for OEM drum front brakes, the job is the same.
P/N UP37080, NAPA rear wheel cylinders, 1966 Impala. $9.99 each
P/N NBF35032, DOT 3 brake fluid, $4.99
P/N CRC 091847, Brakleen, $2.39 each
Time spent: 45 minutes
Jack up the rear of the car and set the frame on jackstands or blocks. Remove the rear wheels. Chock the front wheels, release the parking brake, and place the transmission in neutral.
Remove the drum. Depending on how tight the brakes are set, you may need to spin the drum while pulling on it for removal. If it’s been in place for a while, a few raps with a big hammer on the face of the brake drum will help break it loose — just don’t hit the lug studs.
Here’s what you’ll be working with. It’s important to note the placement of the springs so that everything will go back together the same way it came apart. It helps to only do one side at a time, as the opposite side can serve as a roadmap for reassembly (or tell you where any leftover parts are supposed to live).
Before going any further, you’ll want to clean everything. I like standard Brakleen in the green (non-chlorinated) can. Put on gloves, put a pan under the assembly, and hose it down. This will remove most of the brake dust and any grease or brake fluid that’s built up over the years.
The ease of this job really comes down to having a good brake-spring tool. I’m partial to Snap-On P/N 131A because of how well it works. You can buy similar versions at Sears or even Harbor Freight. Any of these will get the job done. The alternative? Vise Grips, screwdrivers and a lot of swearing.
This end of the tool is your best friend when it comes to removing the two upper drum springs. Note the lip.
Place the tool over the peg at the top of the drum. The tool lip should be inside the open end of the spring hook. Then rotate the tool until the lip digs under the spring hook, and keep turning it until it is pointing away from the spring coils. Pivot the tool handle toward the spring and the spring should pop right off.
Repeat the process with the other spring, and be careful not to lose any parts that might drop.
Each brake shoe is held to the backing plate with a retainer spring and a pin. We used a special brake tool to remove them — just hold the pin in place in the backing plate with your hand, push on the tool to compress the little spring, and twist.
With the retainer springs out, the whole shoe assembly can drop down and hang on the parking-brake cable. If your shoes are worn, you can replace them easily now.
Remove the wheel cylinder’s shoe actuator pins by pulling them out of their rubber recesses at the wheel cylinder.
There are two bolts that hold the wheel cylinder to the backing plate (A), but you’ll want to loosen the brake line (B) first. Hit the fitting with some penetrating oil, such as PB Blaster, before trying to turn it. And be sure to use a line wrench so you don’t round off the nut. In our case, size is 3/8-inch. Get it loose, but don’t remove it yet.
Once the line is loose, remove the two bolts holding the cylinder in place. Ours were ½-inch. Then loosen up the line until it’s free and remove the wheel cylinder. Quick tip: Leave the master cylinder cap in place and you won’t lose much brake fluid here.
The new cylinder goes in the same way the old one came out — start the brake line, get it hand-tight, reinstall the two mounting bolts, and tighten the line. Open the bleeder.
Take some scuff pad, clean the two actuator pins and reinstall them. Also note the six flat spots on the brake backing plate. This is where the brake shoes ride. Clean them and then apply some anti-seize to each spot.
Hang the shoe assembly back on the backing plate, making sure to line up the actuator pins inside each brake shoe. Reinstall each drum retainer pin and each spring clip to hold the shoes in place. Refit any other components you removed.
The other end of the brake tool is for spring installation — the tooth on the end of the bend makes the job a snap.
Feed the spring over the tool, and hook the tool’s tooth on the peg where the spring needs to go. Then pry up. The spring slides down the tool and into place.
Take another quick look at all the components to make sure everything is placed as it was before you tore it apart. This is also a good time to adjust your brakes if you need to. Then replace the drum and close the bleeder. Repeat the entire process on the other side.
Crack open the master cylinder, and if you find the fluid is dirty, suck it out with a syringe or a vacuum bleeder and refill it with clean fluid before bleeding your brakes. No sense in pushing dirty fluid through the lines.
Grab a buddy and put him in the driver’s seat, and then get under the car on the passenger’s side. Have your friend pump the pedal until it gets hard and hold. Open the brake bleeder valve on the new wheel cylinder to bleed out air from the lines, close the valve, and have him let off the pedal. Repeat until there’s clean, clear fluid from the bleeder and no air bubbles. Then do the other side.
Double-check for leaks, clean up any spilled fluid, top off the master cylinder and reinstall the cap. Reinstall the wheels and torque to spec, then go for a spin. If the car stops and the pedal is firm, job’s done.
Why is this so important? Here’s what the inside of my wheel cylinders looked like, and this car has been rarely driven in rain and always stored inside. These cylinders didn’t leak, so there was no indication that they were full of rust. So for $30 in parts and 45 minutes of your weekend, replace them!