Troubleshoot Your Brakes
An automobile's brake system is essential for the safe operation of your vehicle. Without functioning brakes, it's impossible to slow or stop your vehicle when necessary. Troubleshooting your car's braking system is not always easy to do. Each part of the system must be in good condition for it to work correctly, and recognising indications of problems requires basic mechanical knowledge about how the system works, as well as how to recognise a specific problem.
Steps
- Learn the types of braking systems used in modern automobiles. There are two basic subsystems on passenger cars, the deceleration system, a hydraulically functioning, operator controlled dynamic braking system, and a parking brake system, which is activated by a mechanical linkage and prevents to car from moving while it is parked. Here are specific problems you may observe on each:
- Parking brakes
- Failure to engage. If the parking brakes fail to engage, the car may roll when left unattended.
- Check the distance the control handle or pedal travels. If the control travels its limit and the brake doesn't engage, you either have a broken cable or linkage, or the brake drum/disk assembly is not working correctly.
- Determine if the brake stays engaged when you apply it. If not, the mechanism which holds it engage, either a cam or gear type locking mechanism is broken or out of adjustment.
- Failure to disengage. Make sure the brake disengages when you release it. If the parking brakes fail to disengage the powertrain will be working against the parking brake system when you drive causing it to work harder, wearing and overheating the brake components.
- Sticking drum/rotor components can cause the parking brake to fail to disengage.
- Cables or linkages can cause the system to fail to disengage.
- Failure to engage. If the parking brakes fail to engage, the car may roll when left unattended.
- Deceleration braking components.
- The master cylinder provides hydraulic fluid pressure to cause the slave cylinders to engage the friction component (either shoes or pads, depending on the car's configuration) to engage the drums or rotors which slow the rotation of the wheel. The master cylinder is mounted to the firewall underneath the car's hood on the driver's side. Check the following to determine if you have a problem with the master cylinder:
- Check the fluid level in the brake fluid reservoir. Some cars have a translucent reservoir that allows you to see the fluid through the side, others require you to unscrew or remove the clamps and take the lid off the reservoir. There should be a fill line and add line marked clearing on the side of the reservoir.
- Check the area around the master cylinder for leaking brake fluid. This can indicate a damaged reservoir or the seals inside the master cylinder itself leaking and allowing the fluid to escape.
- Slave cylinders cause the brake shoes or pads to engage the drums or rotors. They are located on each axle, either on the rotor assembly or inside the brake drum, depending on which system your car utilizes.
- Check each hub for leaks. You can usually do this by looking at the back of each wheel to see if there is evidence of fluid dripping or accumulating on the inside surface of the wheel assembly.
- The master cylinder provides hydraulic fluid pressure to cause the slave cylinders to engage the friction component (either shoes or pads, depending on the car's configuration) to engage the drums or rotors which slow the rotation of the wheel. The master cylinder is mounted to the firewall underneath the car's hood on the driver's side. Check the following to determine if you have a problem with the master cylinder:
- Parking brakes
- Isolate braking problems by test-driving the car. You will want to find an empty parking lot or quiet side street to do this.
- Check the brake pedal travel by starting your engine and applying pressure to the pedal while the car is in the park or neutral position.
- Begin by pressing gently and seeing how far the pedal moves before encountering resistance. Normal travel varies from one car to another, but generally, should not be more than 1/4 of the distance from its highest position and the floor of the car.
- Press harder on the brake pedal and hold a steady, firm pressure to see if the pedal fades, or gradually begins to move downward while you hold it.
- Pump the pedal rapidly a few times to see if it returns to the same position under pressure each time. If the pedal stops at a higher position when the brakes are pumped, you may have air trapped in your brake lines.
- Release the parking brake and put the car in Drive or first gear and engage the transmission by releasing the clutch.
- Listen for scraping or squeaking sounds from the car's axles while the brakes are not in use. There are a number of moving parts in action when the car is rolling including the rotors, bearings, and gears, so some sound is normal, but hard scraping sounds or squeaking may indicate a brake problem.
- Press down lightly on the brake pedal and listen to see if any sounds you hear increase or disappear. A steady rubbing sound indicates uniform contact of the brake components, where an irregular scraping or rubbing sounds indicates a warped brake rotor or drum.
- Check the brake pedal travel by starting your engine and applying pressure to the pedal while the car is in the park or neutral position.
- See if the car decelerates normally. Be particularly alert for vibrations or a change in resistance felt in the brake pedal. This is a warning there may be air in the brake's hydraulic system.
- Accelerate your car to as safe a speed as possible in your location, up to about {{safesubst:#invoke:convert|convert}}, and apply the brakes stiffly. Observe if the car's wheel seems to pull in either direction. An ineffective brake will cause the car to pull to the opposite side, whereas, a sticking brake will cause the car to pull sharply to the side the brake is sticking on.
- Inspect the visible components of your car's brake system. Park your car on a firm, level surface, preferably on a paved driveway or garage floor. Chock the wheels, and raise one wheel with a floor jack if available. Install jack stands if you are going to work on wheels while they are elevated. (For spoke type wheels, brake rotors may be visible while the wheel is on the ground.)
- Look at the surface of the car's brake rotors (if equipped with disc brakes). They should be smooth and shiny, with a uniform silver color. Purple or bluish discoloration indicated they have been overheated, roughness, swirling groove, or splotchy and grainy surface appearance indicates abnormal wear or rotor warpage.
- If the wheel is lifted off the ground, try to rock it to see if there is any unusual movement in the wheel bearings assembly. Rotate the wheel so you can listen for sounds of uneven brake contact. Now have an assistant engage the brake and check to see if the wheel becomes immobile.
- Check your brake fluid. It should be somewhere between the full and low mark. Never "top off" your brake fluid if it's not below the "too low" mark. As the brake pads naturally wear down, the piston pushing them against the rotor will adjust, drawing more fluid. Installing new pads resets the piston to its original position. "Topping off" the brake fluid when pads are worn may cause overflow and other issues once new brake pads are installed.
- Replace your car's brake pads. If you hear a squealing or grinding noise when you apply the brakes, it may be a sign that you need to replace your brake pads. Excessive brake dust on your wheels is an additional sign of brake pad wear. Grabby brakes or brakes that seem to vibrate can indicate that your pads are worn out, too. It's often wise to turn the rotors or replace them when you replace your car's brake pads.
- Ask a mechanic to test your brake power boost unit. A faulty brake power boost unit causes the brake pedal to depress more than usual in order to activate the brakes.
- Check your car's vacuum system for leaks. If your brake pedal is hard to press down, it's likely that your vacuum system needs repairing.
- Bleed the brake fluid from your car and replace it with fresh fluid. Contaminants in your brake fluid may cause your brakes to function incorrectly. If your brake pedal pushes down further than normal to activate the brakes, it may be a sign of contaminated fluid.
- Examine your brake lines and replace any damaged or broken lines. A hard to press brake pedal is an indicator of a blocked brake line.
- Install a new master cylinder. If your brake pedal seems to have no pressure and your car doesn't brake well, you might need a new master cylinder.
- Inspect your car's brake discs. Bad discs result in grabby brakes or a vibration when braking. One disc may be the problem, or all of them may need to be replaced.
Warnings
- Be very careful with brake fluid, as it will strip off your car's paint incredibly easily. If any fluid gets on your paint, wipe it off ASAP.
- Brake dust can (and often does) contain asbestos. NEVER clean out your brakes with compressed air, as that will send the dust airborne and you will breathe it in if you're not wearing a proper respirator. Clean them using brake cleaner or water in a pinch.
