Why is brake caliper maintenance so important?
For anyone wondering what a brake caliper is, it essentially houses the brake pads and pistons. It allows the hydraulic pressure to be transferred to the pistons which press the pads against the brake discs, generating the friction needed to slow the vehicle down.
If any of its components get damaged or they seize up, there will be a significant reduction in braking efficiency and an increased risk to those inside the vehicle. The parts need to be maintained and lubricated regularly to keep things running smoothly and inhibit corrosion.
Symptoms of bad calipers
- Pulling to one side
The vehicle may pull one side when braking as a result of damaged, corroded or jammed moving caliper parts. If the pistons seize up and fail to retract, it will prevent the pads from making contact with the disc or releasing.
- Uneven brake pad wear
If you notice that the brake pads are thinner on one side, it could be due to a sticking slider pin or piston. This is often caused by rust or fouling. If this occurs, the pads may not be pressing against the disc fully, causing them to drag along it.
- Brake fluid leaks
This is a common symptom of a faulty caliper. The seals are exposed to extreme heat during braking and gradually degrade as a result. You may notice fluid leaking out from the caliper’s seal or boot, or spot pools of liquid around the tyres.
- Decreased braking power
If any of the key components of the system are not working properly, you may see a decline in stopping power. This means that you may need to put in extra effort to bring the car to a halt, potentially increasing the vehicle’s braking distance. This could pose a safety risk.
- High-pitched squealing, scraping or grinding sounds
Abnormal noises coming during braking can be a sign of a sticking or loose caliper, or severe corrosion. If the pads are worn down due to a caliper fault, you may hear a metal grinding or screeching sound.
- Unusual odours
A faulty component could cause increased friction. As a result, the parts get hotter and hotter, causing a burning or chemical smell. This may appear if there’s a leak or the pad material starts to break down.
Cleaning and lubrication
As rust and grime build up, the moving parts of the caliper can get blocked up and jammed. Keeping the component rust-free, clean, and well oiled is therefore key to avoiding brake failure.
The cleaning process:
- To clean the caliper brackets you will need to gain access to them first by removing the wheel. Follow the detailed instructions in the vehicle’s repair manual to find out how to remove the caliper. It is also advisable to remove the brake pads before working on the surfaces so that they don’t get damaged or contaminated.
- Remove the guide pins and guide plates or clips before cleaning. Carefully remove the rubber boots. If the components are damaged, they will need to be replaced afterwards.
- You can start by removing the rust by hand using sandpaper and a wire brush or by using a power tool with a wire wheel for quick results. IMPORTANT: always wear eye protection and a mask to protect yourself from the brake dust. You may also choose to treat the brackets with a brake cleaner to remove stubborn contaminants.
- Some caliper parts will need to be lubricated before reassembly.
Lubrication:
- Grease the guide pins where they meet the rubber boots with a suitable silicone lubricant. Most of the silicon-based products are safe for rubber.
- Use a high-temperature Molybdenum Disulfide for metal-to-metal contact points, such as where the brackets meet the guides. This will prevent noisy brakes.
- IMPORTANT: make sure that none of the lubricant gets onto the brake pads as this could make them ineffective.
How to replace brake calipers
If it’s not possible to repair the part by replacing the seals or hoses, removing rust, or disassembling it and cleaning it thoroughly, it may need to be replaced. It is possible to do this yourself, although it is generally not recommended if you do not have a high level of experience and the skills for this critical job.
Here is a general replacement guide:
- While the car is parked on a flat surface, loosen the lug nuts on the wheel with a lug nut wrench. Then use a jack to raise the vehicle and lower the vehicle onto jack stands.
- Secure the wheels that remain on the ground with wheel chocks to prevent the car from rolling. Once you’ve done this, remove the nuts and then the wheel.
- Place a drain pan below the old part before slowly unscrewing the banjo bolt and removing the brake line. Next, you will need to plug with a rubber cap or seal to prevent fluid loss.
- The next step is to unscrew the old mounting bolts with a socket wrench. Once they have been removed, the old component can be demounted.
- Take the brake pads out of the bracket (not required for floating calipers).
- Align and install the new part. Start by screwing the top bolt to make it easier to line up the holes. After it is installed, you will need to reinstall the brake pads.
- Tighten the new mounting bolts to the correct torque. This is usually specified in the vehicle’s repair manual.
- Remove the cap on the brake line and reconnect the hose.
- Next, bleed the brakes via the bleeder screw. Loosen the screw and then tighten it again. Place one end of a flexible hose over the end of the screw and the other one in a jar or other container. Fill the container with fluid so that the end of the hose is covered. Get an assistant to pump the brake pedal a few times before holding it down. While it is held down, open the screw.CAUTION: the fluid will pour out fast, so be careful and make sure to protect your eyes and skin. Tighten the screw before releasing the pedal. You may need to repeat this procedure a few times until there are no more air bubbles in the fluid.
- Fill up the master cylinder with new fluid.
https://www.bestpartstore.co.uk/brakes/brake-calipers
https://www.knowyourparts.com/technical-resources/brakes-and-brake-components/brake-caliper-cleaning-and-lubrication/
