In restoring a classic car you'll eventually start working on the brakes. As soon as you find where it's hiding and decide on whether to overhaul, restore or replace, you'll need to apply some elbow grease and really put some effort!
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Don't lose heart, though. Here's what you'll need to do to get things started.
Back in the day, it was common practice for car manufacturers to use asbestos on their brake shoes. Today, auto hobbyists must exercise caution when working on classics as it could still contain this toxic substance. When taking apart brake assemblies, it's best to do regular vacuuming in order to minimize your chances of coming in contact with asbestos dust. Wear a dust mask until you're sure that all asbestos have been cleared out.
It's also important to determine the type of brake and how you want to go about restoring it. Do you have an old mechanical, a new hydraulic, traditional drum or modern discs? Does the classic car have dual or a single hydraulic system? Are you planning to add or change suspension, air conditioning or horsepower?
You'll need to address these vital questions before you can even start working on the car’s brakes, as it will serve as your guide to which parts you'll save and which ones you'll throw out. For classic car purists who want to go 100% original, then it's a clear-cut path of rebuilding what you have. To those who want to modify and for people who intend to use the car for daily drives, then you'd be better served with a modern brake upgrade, i.e., larger wheels, power assist, better brakes, etc.
Cleaning and Assessment
Now turn your attention to the master cylinder. Prep the exterior using mineral spirits and follow it up with a good wash of soap and water. After drying, pop out the cover, the pushrod and any attached bleed screws and seals. Remove the inner piston(s) and clean the exterior using either alcohol or plain soap and water. Remove any brown sludge with plastic or wooden chopsticks to prevent scratching and damage.
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Using a bright light, inspect the cylinder closely and look for major scratches, pitting and rust. How badly the pit is will determine the next move, i.e., re-sleeved, honed out or discarded and replaced.
Re-sleeving is a process where the seals and piston gets a new inner surface, done by reaming the cylinder using a milling machine. Professional shops can do this work and charge per job or by the hour.
Ultimately, the decision comes down to your classic car's rarity. For models like the V-16 Cadillac, the Tucker or anything similar, the costs of re-sleeving is often well worth it. Fairly common models like the Mustang will often warrant a replacement if the cylinders are severely pitted.
The good news is that pitting is a rare occurrence in most classic car projects. Cylinders can be honed out using an electric drill and an hone that's sold in most parts shops. Before honing, apply some brake fluid to the cylinder and adjust the tension spring to fit in snugly along the cylinder walls. Set the drill to rotate slowly and run the honing stone on the cylinder's surface in an up-and-down motion until the scratches and pitting disappear. Less honing is more, as you wouldn't want to make the diameter big enough that it can't prevent leaks.
Wash excess brake fluid using alcohol when you're satisfied with how the cylinder wall looks. Use paper towels to fill the excess space and to protect the cylinder until it's ready to run.
Then comes the exterior part. Use a wire brush until the surface is clean and free of rust. Prep the surface with alcohol or mineral spirits, then apply some metal prep to de-oxidize the metal. After priming, coat the cylinder with your preferred paint color. You can also opt for powder coat here, but make sure to fill up the bore with paper towels and tape openings shut before applying paint. If you're looking to paint your calipers and wheel cylinders the same color, then it's much more efficient to wait and do them all at once
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Wheel cylinders are fairly simple to restore, but it gets a bit complicated if you see a stepped design. Start by cleaning the cylinders and removing the piston(s) and seal. Clean the bore and hone as needed. Paint the exterior while protecting the insides with paper towels.
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Brake calipers can come in different designs. You may see anywhere from one to four individual cylinders, all of which need to be cleaned. If any of the cylinders are severely pitted, then it's better to do a re-sleeve or replace the whole thing.
Take extra precaution when taking the calipers apart as they could be bolted together. Also, don't mix different halves as it will always result in leakage; the same applied to the bolts that hold each cylinder in place.
Hone the caliper cylinders as you did the master or wheel cylinders. Wipe them clean and prevent dust and grit from getting inside.
Getting your brakes like new
Investing in the highest quality rebuilding kit you can get your hands on is well worth it. Getting the best kit for disc brakes is of the utmost importance because the rubber seal's resilience will dictate how well your brake calipers work.
Lay out all the new parts in ample space with a layer of paper towel, plastic or newspapers underneath. Wash your hands before putting on latex gloves and make sure there's no dirt anywhere in the immediate area.
Then comes the rebuilding part. Put everything back together in reverse order of how you took it apart. Consult your rebuild kits instructions or the shop manual if you're at a loss; don't forget the small springs, ball bearings and clips. Coat each part with brake fluid but make sure the external parts stay fluid-free.
Mineral-based or silicon fluids?
Brake fluids made of mineral are solid favorites even among car manufacturers. The only problem with using mineral is that it accumulates water in the atmosphere, which eventually forms pits, rust and buildup. Car owners will need to flush old fluids out and get new ones in every few years to keep the system in optimal condition.
Silicon fluids are relative newcomers in the automotive industry. It's highly resistant to water and can act as a permanent brake fluid. The problem with silicon-based products is that they have higher viscosity and capillary action, which can result in leaks, seepage and foam-ups while in the process of refilling. Moreover, most car owners report a spongy brake effect when their systems are filled with silicone fluids.
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All in all, it may depend on your classic car's make and model in your choice of brake fluids. Silicon fluids work extremely well on the '69 Camaro, '65 Mustang and the Jaguar XKE, while proving to be detrimental to the '66 Corvette, Sunbeam Tiger and the Jaguar XK 120.
As a general rule, silicon fluids are best for rebuilt systems that have perfect cylinder walls. You're generally better off with mineral fluids if your classic car has an undersized braking system in respect to the car's weight. If you're on mineral, then we don't recommend you replace it with silicone fluids.