How do I know if my brake master cylinder is bad?

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asked Jul 19, 2023 in Repairs/Maintenance by Flocraz (19,470 points)
How do I know if my brake master cylinder is bad?

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answered Nov 30, 2023 by Caldecott (25,160 points)
The signs that your brake master cylinder is bad includes spongy feeling brake pedal, brake pedal that goes to the floor, loss of braking power or low brake fluid.

When a brake master cylinder goes bad it will not distribute the brake fluid pressure properly and cause a spongy, mushy or sinking brake pedal when the brake pedal is pushed down.

After installing a new master cylinder you do need to bleed the brakes to get rid of the air in the brake system or the brakes can be spongy or go to the floor.

Whenever you open the brake system to the air the air must be bled out of the brake system for the brakes to work properly.

You can bleed the brakes by pumping the brakes and opening the bleeder screw with the help of another person or use a one person brake bleeder tool.

The cost to replace a brake booster and master cylinder ranges from $300.00 to as much as $1,000.00 depending on the make and model of the vehicle.

Replacing the brake booster and master cylinder yourself is cheaper and costs around $300.00 or less for the parts and your time.

You will need to bleed the brakes after replacing the brake booster and master cylinder as well.

Master cylinders are not generally overhauled but instead they are replaced.

Overhauling or rebuilding a master cylinder can be more expensive or cost near as much as just replacing the master cylinder with a new one.

A caliper or brake caliper costs around $50.00 to $150.00 each depending on the vehicle.

You can buy brake calipers online cheaper than you can in an auto parts store.

Brake calipers don't fail very often and some brake calipers may last the life of the car or vehicle.

In some cases brake calipers may fail within 5 to 10 years or 200,000 miles or so.

You can just replace one caliper if only one is bad.

However if you can do so it's best to replace both brake calipers at the same time but if you can only do one brake caliper at a time and the other brake caliper is working fine then it's okay to just replace the one brake caliper.

A seized caliper can catch fire if the caliper does not release from the brake rotor.

Eventually the friction from the brake pads and rotors due to the seized caliper can cause the heat to build up hot enough to where there could eventually be a fire.

A bad caliper can cause shaking or pulling especially if the caliper is sticking or the brake caliper is loose.

The shaking and pulling will be noticed when you're driving when it's caused by a bad brake caliper.

Calipers can fail due to age and natural wear and tear and when the seals degrade or contaminants in the brake fluid.

Also driving with worn out brake pads or warped rotors can lead to the brake calipers failing.

Replacing a broken or bad brake caliper takes around 1 hour to 2 hours although in some cases it may take up to 3 hours.

A brake job should take between 1 hour to 3 hours depending on how much work needs to be done.

If replacing just the front brakes or back brakes then it may take only 1 hour to 2 hours but if replacing all 4 brakes and doing a complete brake job it can take 3 to even 4 hours.

A bad rotor or bad brake rotor will sound like scraping or grinding noises.

You can tell if a rotor needs to be replaced by the sounds and feel of the rotor.

If the rotor makes a grinding noise or the rotor is causing vibration then it is likely warped and needs replaced.

If you take the wheel off and look at the rotor and it has any severe cracks, is worn down or is warped then the brake rotor should be replaced.

A warped rotor will sound like grinding noises or scraping noises and a squealing noise when you apply the brakes can be a sign of worn brake pads.

You can most often feel a warped rotor while driving when you apply the brakes as the warped rotor can cause pulsation in the brakes and vibration in the steering wheel.

In some cases there may be some vibration when driving down the road with the warped rotor.

The symptoms of bad rotors while driving are pulsation and vibration of the steering wheel, high pitched squealing noise when braking and even shaking of the steering wheel.

Other signs of bad rotors when driving are the vehicle taking a long time to stop and loud bangs or clunks when you apply the brakes.

Your front end can clunk when you go over bumps due to worn bushings in sway bars, worn bushings in shocks, worn ball joints or loose lug nuts.

Damaged or worn out control arms may also cause the front end to clunk when you go over bumps.

When a car makes a clunking sound when you brake it can be a sign that the brake rotors are warped or the brake calipers are loose.

Brake pad shims, loose brake calipers and incorrectly torqued wheels can also be a cause of a car clunking when you brake.

Make sure the brake calipers are tightened and make sure the lug nuts are also tight.

A car that is shaking and knocking when you brake is most often caused by a damaged brake rotor or warped brake rotor.

A loose brake caliper along with the warped brake rotor could also cause the shaking and knocking noise when you brake.

If the brake rotor is warped then it will need replaced.

Shaking and clunking when you brake can also be a sign that your brake pads are worn and needs replaced.

If you hear a squealing or squeaking noise such as metal on metal noise when you apply the brakes then it's a sign that the brake pads are worn as the brake pads have a little piece of metal that makes contact with the rotors when they are worn to indicate you need to replace your brake pads.

A knocking noise in front wheels can be caused by bad tires or a bad tire.

If the tires are bad then a knocking sound can be heard in the front wheels or when the tires are unbalanced or misaligned.

A broken tire belt can also cause a knocking noise in the front wheels.

If the tires are good then another cause of the knocking noise in the front wheels could be loose lug nuts, loose brake caliper or even bad wheel bearing that causes the wheel to move back and forth as in side to side.

Worn ball joints could also cause a knocking noise in the front wheels that occurs especially when you hit a bump.

Another cause of knocking noises in the front wheels can be worn shocks.

A clunking, rattling, or squeaking noise from your vehicles front end while driving can be annoying and unnerving.

Oftentimes, the clunking, squeaking or rattling noise means there is a problem with your vehicle's suspension system.

These sounds typically occur when driving over uneven surfaces, bumps, or potholes.

You're likely hearing a knocking sound from a noisy wheel bearing because it isn't rotating as freely as it should.

If you hear a thump towards the front of your car whenever you accelerate, it's probably a problem with either your starter motor mount or transmission mount.

Though small, transmission mounts have a huge impact on performance and the overall quality of your drive.

If you hear a clunking noise that is especially prominent when you drive over potholes or speed bumps, you probably have a problem with your shock absorbers or your suspension.

Continuing to drive with a broken or faulty shock absorber is a bad idea for the health of your car.

Commonly, engine knocking occurs because of a buildup of oily carbon deposits inside the combustion chamber.

This can be caused by burning oil or incomplete combustion from misfires, which coats pistons, cylinder heads, and other parts of your engine with residue.

The first sign of wheel bearing failure is excessive vibration.

Following this, the bearing will begin to heat up past acceptable levels and produce excessive noises, either high-pitched or grinding.

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