A car’s brakes live a hard life. They’re subjected to rapid heating and cooling cycles as part of normal use. They’re out in the weather picking up all kinds of road gunk and debris and they need to be a completely sealed system to work, so there’s very little margin for failure. The good news is that by now, disc brakes are ubiquitous and the technology is largely perfected so we don’t have to worry about them often, but things do still go wrong.
How Disc Brakes Work
Before we get to that, though, let’s talk about how a disc brake system works. When you press on the brake pedal, incompressible brake fluid builds hydraulic pressure inside the master cylinder. This master cylinder takes the hydraulic pressure created by the driver’s foot and transfers that energy through sealed brake lines and hoses to the car’s brake calipers.
Those calipers have a much larger diameter bore than the master cylinder, so the force is magnified many thousands of times from the pressure applied at the pedal, and the brake caliper piston moves outward, pushing the friction material of the brake pads against the spinning brake rotor. The energy of the vehicle is transformed from inertia to heat, which is dissipated through the rotor, pads, and brake fluid.
Leaky Calipers
The braking system can only function properly when it is totally sealed and free of air. That’s because air is compressible, while brake fluid is not. If there’s a leak in the system, the fluid can escape and some of the pressure that would otherwise go to act on the brake piston will be lost. The most common places for leaks are on corroded metal brake lines and the brake caliper seals. It’s the latter that concerns us here.
Brake caliper seals are made of special rubber that can deal with the huge operating temperature range of disc brakes, but ultimately they age and can crack, split, or simply lose the elasticity they need to seal against the metal piston. Many brake calipers can be rebuilt with new seals if the old ones fail, but for most people and shops, it’s more economical to simply replace the calipers with new or factory-refurbished units.
Brake Fluid, Water, and Stuck Calipers
Earlier, I talked about brake fluid and how it has special chemical properties. The most important to us as drivers, especially if we drive heavy or high-performance vehicles, is brake fluid’s elevated boiling point. Water boils at 212 degrees Fahrenheit, but new, fresh-out-of-a-sealed-container DOT 3 brake fluid, which is the least expensive and least performative type, won’t boil until 401 degrees Fahrenheit.
We make a point of saying completely new brake fluid because it’s hygroscopic, meaning it loves water and will pull moisture from anywhere it can, including the air. Brake fluid’s boiling point is listed as both a dry boiling point and a wet boiling point, with the former being new and the latter after the fluid has reached a concentration of 3.7 percent water by volume. Even that small amount of water has a huge effect on the boiling point, often cutting it in half.
The other major downside to having water in a car’s brake fluid is that water is corrosive and many of the major components of your braking system are made of steel or iron. If a vehicle is used for an extended period of time with a high degree of water in its brake fluid, it can cause the brake caliper piston to rust in its bore, which will lead to a stuck caliper.
A stuck caliper will manifest either by causing a wheel to become stuck and drag or, more commonly, causing one brake pad to wear prematurely. This will also typically cause the vehicle to pull to one side when the brakes are applied. As with the leaky caliper, the fix here is typically rebuilding or replacing the brake caliper and completely flushing the brake system of old, water-laden fluid.
How To Avoid Issues
Changing brake fluid every two years is a good way to avoid having issues with internal corrosion and stuck calipers, but some manufacturers and some higher-performance brake fluids (like for racing) will mandate that it’s changed more often. Sometimes as frequently as every six months, or any time a brake fluid tester shows a water concentration of at least 4 percent.
If a brake caliper needs to be replaced, it’s best to replace in pairs. For example, if the right front caliper is leaking, then get the caliper for the left front and replace it at the same time. This helps ensure even performance and reduces the risk that your other caliper will fail soon after. Doing it this way will also save a little bit of money on labor, because any time the system is opened to the air (not counting the reservoir cap), the whole system has to be bled, so why do it twice?
How To Inspect For Issues
The best way to inspect brake calipers is generally to lift the vehicle safely on jack stands and remove the wheels, but it’s also possible sometimes to sneak a peek behind the wheel by turning the car’s wheels and getting a flashlight in there. Leaks are usually easy to spot, but uneven pad wear can be harder to see.
Beyond a visual inspection, it’s critical to pay attention to the car when driving. If the brake pedal is pressed and it sinks further than usual or goes all the way to the floor, that’s a sign that something is wrong. This is also true if the car pulls to one side or the other when the brakes are applied. Cars with stuck brake calipers can sometimes make squealing or grinding noises if the brake pads are worn far enough, but don’t count on this always being the case.
Finally, the most important thing is to remember that if something is not feeling right with a car’s braking system, don’t wait to inspect it or have it inspected by a qualified mechanic. Ignoring the problem will not only make you a danger to yourself and others on the road, it’s also likely to cost more to fix the longer the repairs are put off.
Find Everything Needed for a Brake Flush at CARiD
Making it easy to find everything needed for all kinds of regular maintenance, CARiD provides a shop-by-service feature. When it comes to replacing brake calipers, users can simply enter their vehicle year, make, and model, and the site will show compatible brake calipers as well as brake pads, fluids with different DOT ratings, brake bleeders to help flush the system, and other related items.
For more help finding the right brake fluid and tools needed to properly do a flush, check out the CARiD live chat tool, where experts are standing by 24/7 ready to help.
