If it feels soft and spongy, something is wrong. And since brakes are a vital part of controlling your vehicle, you should immediately get your vehicle checked to diagnose the issue. When you press down on your brake pedal to slow or stop your car, the master cylinder responds by pushing brake fluid into the brake lines to activate the brake piston. The caliper piston then closes on the rotor and squeezes the brake pad. If your car uses drum brakes, an actuator is activated in response to brake pedal pressure.
This pushes the shoes outward against the inner surface of the drum to slow your car down. Essentially, irrespective of which type of brake system you use , the entire process starts with you pressing down on your brake pedal. In a normally operating brake system, you should feel little to no difference in the firmness of the brake pedal during any part of the braking process.
However, there are several reasons that could lead to a spongy or soft pedal. When releasing the brake pedal, the returning motion sucks in air, and you experience a pedal that goes directly to the floor with minimal resistance.
Some cars have a built-in dashboard indicator light that lights up when the brake system is compromised. Your warning light could be notifying you of anything — from an engaged parking brake to the car running low on brake fluid. To be safe, consider having all your brake components checked whenever the warning light flashes. If you need to repeatedly pump your brakes to slow your car down, check your brake system for a fluid leak.
If the brake warning light is not on and there are no visible brake fluid leaks, your master cylinder may be worn or leaking internally. Your braking systems rely on evenly distributed hydraulic pressure to bring your vehicle to a stop. Any disturbance in the balance of pressure will result in your car needing more time, distance, or effort to stop itself. An air bubble can prevent the brake fluid from flowing properly and compromise the hydraulic pressure of your brake system.
Air will generally always find its way to the top. This could be simply in a brake line that has a funny bend in it that goes in an odd upward location or it could be trapped within a high point in a caliper above the brake bleeder.
To remove the air in a caliper, it may be necessary to remove the caliper and move it around to try and get the air pocket to get into a place that bleeding the brakes will solve it. If it is felt that air is in the system and you are having difficulty in finding it, we use a simple trick of blocking off portions of the brake system. To do this, block off the front calipers and apply the brakes and then block of the rear part of the system and apply the brakes.
If the pedal improves and loses that soft feeling, you can just about guarantee the whereabouts of the air and from there can at least start to narrow down your search to the front of the vehicle or the rear.
The air pocket can still be there no matter how much fluid gets pushed through the system if the air pocket is in a caliper or line that has an odd situation.
This kind of seems obvious but definitely worth mentioning as there are some catches. The first part of this is the obvious and visible brake fluid leaking from a port or fitting. Because the fluid is pushing out of the system, the system never reaches a point where it can start to move the pistons within the calipers or wheel cylinders and therefore causes a soft pedal.
The fix here is the quite obvious of fix the leak and follow that up with a complete bleeding of the brake system to remove any and all leaks from the system. The catch part of this is when there is a leak at a fitting but no fluid coming from the port of fitting. It is possible for a fitting to actually pull air when the pedal is returning back to its resting position. This air entering the system is going to obviously create a situation where the brakes will need to be bleed again.
Before bleeding the brakes however, it is necessary to find the faulty fitting and correct the problem. Brake fluid is just like the oil in your engine and other mechanical systems in your vehicle.
It is recommended to change your brake fluid at a max, once every two years. If the fluid goes too long without being changed, the fluid can actually absorb moisture into the system and therefore then change the compression characteristics of the fluid. If you have overheated your brakes during spirited driving or towing, the fluid can boil and create gas that will make your pedal feel spongy.
This is because gas, unlike fluid, can be compressed. Each of your brake calipers or brake drum wheel cylinders will have a bleeding screw that will allow you to force air out of the lines using the brake pedal or a brake bleeding kit and the proper bleeding procedure for your vehicle.
Soft or spongy brakes can be frightening, but you can usually correct the problem without too much hassle. Photo courtesy of Wikimedia Commons. Know How.
Having been bitten by the car bug at a young age, I spent my formative years surrounded by Studebakers at car shows across Quebec and the northeastern United States.
But just like brake pads, brake fluid can wear thin over time. Can't remember the last time you had a brake service? Then it could be that old brake fluid is causing the poor brake performance. Or, you could have a possible leak causing your fluid to be low. Either way, get it checked out! This is one of the most common causes of spongy brakes. Unevenly distributed hydraulic air pressure causes the system to become out of balance, which causes a soft brake pedaling issue.
When your braking system isn't working as well as it once was, it could be the master cylinder is malfunctioning. Its job is to distribute hydraulic pressure see above-Air in Brake Lines which distributes the brake fluid where it's needed to stop your vehicle.
However, over time, master cylinder seals leak or break.
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