How to Rebuild C3 Corvette Brake Calipers on a Budget
Believe it or not, this caliper in the foreground looked just like its mate before we spent a weekend bringing it back up to spec. The only tool we used that you might consider specialized is a bead blasting cabinet to achieve this result. So, if we can do it, you can too.
The whole point of turning wrenches on your own car is to experience the satisfaction of getting behind the wheel of a car or truck you had a hand in building. Admittedly, sometimes we all do it because a buck must be stretched, and if we didn’t do it ourselves it wouldn’t get done at all. Sometimes we do it because there are no options in the marketplace that match what we’re trying to build. But even when both of those things are true, for most of us just getting into the shop and spending some time working with our hands is pure therapy.
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As you can see the Corvette project is a frame-off rebuild. Practically everything needs to be rebuilt or replaced. That means the budget is stretched thin, and while the entire brake system looks like it should be thrown on the trash heap, we elected to replace the rotors with stock replacements and take a shot at rehabbing the four-piston calipers. Cheap rebuild kits with new rubber boots, seals, and O-rings to seal the gallery between the two halves of the casting cost us just $17 per caliper.
That’s why we’re taking you along on this little misadventure. The project at hand is a basket case ’80 Corvette that is going back together slowly. Eventually, we plan to bolt up a quality big-brake kit with stopping power like hitting a brick wall. But for now, we’re just trying to get the stupid thing back together and moving under its own power. Every nut and bolt has to be touched, so going top-shelf with every component as the car goes back together would cause the credit card to go nuclear. So, a little common sense had to be applied.
Based on the inspection sticker, the Corvette had sat for the last 10 years, so resting in the elements was the real problem, not wear.
As many Chevrolet fans will note, there are plenty of faults when it comes to the C3 Corvette. Poor power levels, rattly interior components, vacuum lines out the wazoo—you name it. But one area where Chevrolet’s engineers got things right is the brakes. Granted, you won’t find them on any cars at Le Mans, but we’re talking pretty good for the time. Disc brakes all around, beefy rotors, and four-piston calipers at all four corners.
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The calipers unbolt with one big fastener on each end and then split right down the center, giving you access to the pistons. They are held in place with a rubber boot that’s easy to remove simply by getting a screwdriver underneath the metal ring and prying up. These are obviously being replaced, so we weren’t worried about not harming the rubber portion of the boot.
So, we decided to spend a weekend rehabbing the brake calipers on our Corvette to bring them back to their former glory. They looked pretty far gone, but fortunately the Corvette calipers have stainless steel liners. While the rust on the castings looked pretty severe, the critical liners in the piston bores were still in pretty good shape. The rotors, however, were too far gone and were added to the metal recycling pile.
With the boot out of the way, the piston should come right out. You can see the seal around the bottom (wider) portion of the piston. Underneath is a spring that keeps the piston pressed against the back of the brake pad. Notice that it may be crusty, but thankfully there is still a little bit of brake fluid in the bores.
Tag along as we take you through the process of rehabbing these rotors. All the-new components you see used here can be found either online at a company called Zip Corvette or any of the local auto parts chains. We also learned some tough lessons along the way, which we’ll be sharing. Even though Chevrolet never put too many four-piston calipers on their other cars and trucks, there is still plenty that can apply to the single-pot floating calipers that GM put on practically everything else.
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We were not nearly as lucky with the rear calipers. The brake fluid has completely dried out, leaving behind this abrasive residue. This is a sign of trouble, we just didn’t realize how much at the time.The pistons on the front calipers slid out easily, but on the rears the pistons were seized in the bores. We used a pair of smooth jaw pliers to finally pry them out. Despite being careful with the pliers, they still left marks on the soft aluminum pistons. Still, we figured that was OK because the marks were on the narrow end of the pistons that do not contact the cylinder walls and only press against the back side of the brake pads.But it turns out trying to be careful with the pistons didn’t really matter. There was just too much corrosive buildup on the rear pistons (left). For comparison, you can see one of the larger front pistons as it came out of the caliper (center) and how one of the front pistons looked after applying a little elbow grease with brake cleaner and a Scotch-Brite pad. We tried a few different methods to get the rear pistons cleaned, but we just weren’t able to get all that ugly buildup off—especially in the grooves where the fit with the rubber seal must be perfect. It just wasn’t worth the risk to put the calipers back together only to have them leak, so we ordered new pistons and new backing springs for both rear calipers.Unfortunately, we should have waited to order those replacement pistons until after we finished tearing down the calipers. On one of the rear calipers the brake bleeder was seized and broke off despite multiple applications of rust penetrant over the course of a few days. You can see what’s left in this shot where we’re applying heat and doing the old candle wax trick before trying to remove it with an easy out.Despite our best efforts, the rest of the bleeder just wouldn’t budge and we ended up breaking the casting. No big deal; a stock replacement for this was right around $85 online. But we just wish we had waited to order the new pistons and springs, as well as the boot and seal rebuild kits until we knew for sure that the caliper was good.The cylinder liners are stainless steel, so there are no rust issues to deal with. We scrubbed out the cylinder bores with a Scotch-Brite pad to remove any dirt and grime, and then gave each bore a quick pass with a brake hone using fine stones. To eliminate the possibility of contaminating the brake fluid with anything that has a lower boiling point, we used DOT 3 brake fluid as a lubricant for the hone. That’s it in the super high-tech spray paint lid beside the caliper. The lid was just a convenient way to dip the stones into the brake fluid. Afterward, we thoroughly rinsed out any grit left in the piston bores with brake cleaner.Here’s another mistake to avoid. We used shop towels and painter’s tape to either plug or mask off areas we wanted to protect before going into the bead blaster. But the painter’s tape blew off almost immediately. Switching to proper duct tape fixed that issue.The exterior of the calipers has so many compound curves it would have been difficult to get them properly cleaned of rust with a sanding disc. A few minutes in the blast cabinet with glass bead media did the trick almost painlessly. This is an economically priced blast cabinet we picked up from Harbor Freight.This is the result of a couple cans of VHT’s gold caliper paint from Summit Racing. The high-heat paint should hold up well, and we chose gold to mimic the old-school look of the sweet gold Brembo calipers used in NASCAR in the ’90s. At first it came out looking too light (the two calipers on the left), so we added a coat of VHT caliper paint in gloss clear and that darkened the calipers up a bit. (See the two on the right.)Originally, we just purchased the rebuild seals (dust boot, piston rings, and O-rings) kit for the brakes. But after the rear calipers turned out to be in such bad shape, we had to go back and order replacement pistons. Then, of course, one of the brake bleeders broke off in the caliper and we broke the casting trying to get it out. We could have saved some cash had we waited and completed the caliper teardowns to find out exactly what we needed instead of making multiple orders and winding up with replacement parts.This is an original-style seal installed on the caliper piston. Notice how the flange points down. Make sure the seal is fully seated into the groove or there is no way you will be able to get the seal down into the cylinder bore without damaging it.Each piston has a deep groove for seating a lightweight spring. Its purpose is just to keep the piston pressed against the back of the pad and won’t provide much in the way of drag. Since we had so much corrosive material clinging to everything inside the rear calipers, we replaced the stock springs along with new ones to go with the new pistons.The stock-style brake fluid seal has a lip to help create a positive seal against the piston bore. The seal has to point down to work properly, and it can be difficult to get it into the bore when it is in place on the piston. We found that using a thin screwdriver to help work the seal in place as you apply light pressure on the piston helps significantly.Once the piston is in the bore, you have to hold it down while pressing the dust boot in place. We used a socket that was the same diameter to drive the metal ring of the seal in position.Then the rubber portion of the dust boot slots into the upper groove in the narrow part of the piston. The boot/piston assembly on the left is ready to go. The one on the right still needs to be manipulated into the groove.Here, the caliper is bolted back together and ready to be installed on the car. We installed new bleeder screws into the caliper body. This time around a little antiseize on the threads will hopefully keep them from galling again. Right now we’re just using stock replacement brake pads we found on the Internet. They are held in position by the pin running through the center of the caliper body. Once the caliper is bolted up to the car, the pads can be replaced simply by sliding out the pin and pulling the pads right out of the top.The front caliper is all bolted up. We went ahead and invested in quality braided flex lines from Russell Performance Parts because they can be reused even if we eventually upgrade to a performance aftermarket brake system. As you can see, the hose retainer clip on the chassis is new. The old ones would have worked just fine except during teardown we put them someplace safe and now can’t seem to find them.Here we have a caliper bolted to the rear. In case you ever get confused which side of the car the caliper originally came off, just remember that at least one bleeder screw must be pointed up to release any air bubbles when you bleed the brakes.
Sources
Harbor Freight
harborfreight.com
Russell Performance Products
(800) 365-9145
edelbrockgroup.com/russell-performance/
Summit Racing
(800) 230-3030
summitracing.com
Zip Corvette
(800) 962-9632
zip-corvette.com
Click on this issue’s cover to see the enhanced digital version of How to Rebuild C3 Corvette Brake Calipers on a Budget.
