In our last newsletter we discussed wheel maintenance. Before you install those shiny wheels, a brake check is in order. Some Corvette owners are still in the grip of winter which allows time to check out the braking system while Corvette owners in warmer climates should consider scheduling time to check their brakes. We rarely concern ourselves with brake condition until we hear squeaks or grinding or worse yet, the brake pedal goes to the floor. Proper brake maintenance can save lives and major expenses.
Corvettes that accrue just a few miles per year are the most susceptible to brake fluid contamination from moisture intrusion, eventually causing visible brake fluid leakage. This means that low mileage cars should be scrutinized carefully for leaks. We’ll go over the obvious areas of concern in the complete brake system and how to spot trouble before it becomes a major issue.
Early Corvettes are prone to wheel cylinder leakage, which shows up as a wet spot at the bottom of the brake drum. It’s a good idea at the very least to pull the drums off the rear and check for fluid leakage at the wheel cylinders. Pulling back the wheel cylinder dust boots will reveal fluid leakage. If you find the rear cylinders leaking fluid out of the dust boots, the front wheel cylinders are most likely also leaking.
65-82 Corvettes are prone to caliper leakage due to the design, with 4 sealing rings at each caliper. If you see an accumulation of wet dust around the pads or caliper pistons, leaks are occurring. The next step is to gently pull the dust/debris boot away from the caliper piston in question and see if fluid dribbles out. Don’t try to pull the dust/debris boot away from the caliper body itself. The boot is pressed into place and will be damaged! If fluid comes out of any wheel cylinder or caliper, you need to attend to the issue immediately or face the consequences of eventual low or complete loss of brake pedal. 1984 and newer Corvettes have better designed calipers that are very reliable and rarely leak. When they do, severe contamination has occurred.
This brings us to brake fluid maintenance which is often neglected until system damage occurs. Moisture laden brake fluid eventually causes corrosion at the lowest points of the braking system which allows corrosion particles to float around the caliper/wheel cylinder pistons. The slurry of corrosion wears at the seal surfaces causing leaks. 1986 and newer cars are especially sensitive to brake fluid debris in the anti-lock brake controller. The rule of thumb is: the less you drive your car, the more you need to change the brake fluid. Silicone fluid helps keep moisture levels down when used in Corvettes before 1986, but moisture contamination can still occur. Anti-lock brake Corvettes (1986 and newer) cannot use silicone fluid. The higher viscosity silicone fluid will damage the brake controller.
Every two years, the brake fluid system should be bled to flush out moisture and corrosion. Keep the cover on the master cylinder as much as possible. Brake fluids hydroscopic properties allow it to suck moisture out of the air directly into the fluid. The same care should be taken with any brake fluid used to top off or flush the brake system. Missing or loose container caps let moisture into the unused brake fluid, so the new fluid may be in worse shape than what’s in the system now. We have brake bleeding equipment including speed bleeders to help make the difficult task of brake system flushing simple.
Pad and brake shoe wear is usually obvious. The rule of thumb goes like this: if the brake pad material is thinner than the brake pad’s steel supporting pad, replacement is necessary. Scored disc brake rotors or brake drums could indicate worn shoes or pads which would indicate further brake lining scrutiny. Don’t forget to look at the brake hoses for deteriorated or cracked outer rubber casings. Chafing or worn spots on hoses should be checked for possible wheel or suspension rub areas before hose failure occurs.
The final check is for fluid leakage out of the master cylinder itself. Master cylinders have seals at the rear of the cylinder where the push rod applies pressure to the piston. Over time, the same fluid contamination wears at this seal causing leaks. If you find a rust trail or fluid seeping between the master cylinder and brake booster, be forewarned the cylinder requires replacement.
Any way you look at it, spending Saturday afternoon cruising in an early or late model Corvette can be very enjoyable. Absolutely nothing is more gut wrenching than no brake pedal when you need it most. Our series of tech tips should keep you cruising in confidence for many years. Whether you need brake fluid to flush the system or a complete brake restoration, we have the necessary items waiting for you.
This article was written by Chris Petris for Corvette Central.