Question about Cars & Trucks
Light on and ringing when brakesused
The Brake pads need to be replaced. There are 2 indicators for thin brake pads. There is a thin piece of metal which is attached to the brake pad and acts like a finger pointing to the brake rotor. When the pad gets too thin the metal finger starts contacting the rotor when you brake causing an audible squeal. Note that not all brake pads have these squeal guards. The second indicator is a brake fluid level sensor. The fluid level in the master cylinder lowers as the pads wear and when they are worn too low the light comes on. At first it may come on momentarily, especially when the temperature is cold and fluid contracts. Eventually it will come on and stay on. Below is a detailed description of how it works and why you should never add brake fluid to the master cylinder to make your brake light go off.
Your brake fluid provides pressure on a piston which presses the brake pad into the rotor when you brake. Below is a crude drawing:
Brake pedal ==> Brake Fluid===>Piston=> Brake Pad '' Rotor
When you take your foot off the brake the brake pads (and the piston) always maintain the same spacing between pad and rotor. As the surface of the brake pad wears away the piston and pad require more fluid behind them to keep the piston and pad close to the rotor. Otherwise when you press the brake pedal the brake would not engage until it was pressed enouogh to make up for the wear in the pad. You would not want to have to pump your brake a few times in order for it to start working! Anyway, there is a brake fluid reservoir in the master cylinder whose level will drop as more fluid is needed in the brake line to compensate for the wear of the brake pad. Some people think that when their brake fluid level is low they should add more fluid to the reservoir. This will make the brake light go out but it also defeats the purpose of the brake pad warning system. If you add fluid you will not know when the pads are too low and they will eventually wear completely away. The metal backing of the pad will grind directly into the rotors, ruining them and severely impacting the breaking ability of your vehicle. When new brake pads are installed the piston is re-compressed (pushed left in the drawing above) in order to fit in the new thicker pads. This pushes back the break fluid into the master cylinder which then fills to the proper level and the brake light goes out. If you had put in extra fluid to make the brake light go out this extra fluid would overflow the master cylinder when the new pads are installed. Brake fluid will spill over and it is not good for the rubber components in the engine. Don't add more fluid. Just get your brake pads replaced.
Posted on Dec 06, 2014
Heck thebrake fluid level before you go any further ,
Posted on Dec 06, 2014
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Posted on Jan 02, 2017
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