When you slow your vehicle or decide to stop, you depress the brake pedal. Most of the time, the pedal will be firm and you’ll be able to apply steady pressure until you get the desired slower speed, or come to a complete stop. However, oftentimes the pedal may “go to the floor” and you’ll have to pump it a couple of times to get the firm feel that you’re used to. If your brakes must be pumped to hold, there’s a serious issue that has to be addressed.
How the brake system works:
Your brakes work on fluid pressure. If the braking system is not able to build up the pressure required to operate the system, your pedal will feel strange. In some cases, it will be spongy and soft. In others, you’ll have to pump the brakes.
When you depress the brake pedal, the master cylinder sends fluid into the lines, generating pressure. This activates the calipers, which squeeze the rotor on each wheel between the brake pads. Drum brakes operate on a similar basis, but fluid pressure causes the actuator to press the shoes out against the sides of the drum to slow down the wheels.
Obviously, if there is not enough pressure in the lines, this doesn’t happen. However, if moisture has gotten into the system, the result can be similar. Water has a lower boiling point than brake fluid. When it is heated at the brakes, it vaporizes, producing air in the lines (and letting compression – brake fluid cannot be compressed).
Common reasons why this happen:
- Air in the Lines: The number one most common reason for having to pump your brakes to get them to work is air in the lines. This may be because your brakes were recently serviced but not bled properly. It needs bleeding each wheel several times, starting with the wheels farthest from the master cylinder (passenger rear, driver rear, then passenger front and driver front). It can take multiple bleeds to take out all the air from the lines, even after a basic service. The fluid will then have to be topped off.
- Low Brake Fluid: If your vehicle brake fluid is low (and it’s not due to brake pad wear), then the system will be unable to generate enough pressure for normal operation and you may have to pump the pedal. Generally, low fluid is made by a leak somewhere in the system, including at the caliper, the brake lines, or even the master cylinder.
- Failing Master Cylinder: While rare, master cylinder failure does happen. If the master cylinder has started leaking fluid down the back of the engine, you can expect to experience poor brake operation and reduced safety on the road.
- Moisture in the Fluid: If your brake fluid has absorbed moisture (which is very normal over time and through regularly wear and tear), you’ll notice reduced braking performance, including the possibility that you’ll have to pump the brake pedal in some cases.
- Damaged or Missing Bleeder Valve: Each wheel should have a brake fluid bleeder valve on the line near the wheel hub. If one of yours has been spoilt, it’s possible that you’re leaking fluid and allowing air into the line at the same time.
How it is done:
The mechanic will have to inspect the entire brake system, which may need the removal of one or more wheels. The mechanic will also have to check for air in the lines, as well as leaks in the lines and at the master cylinder.
How important is brake repairs?
If your brakes have to be pumped to function, your system needs immediate service. This shows a significant problem, including air in the lines. It reduces greatly your stopping capability on the road, which endangers you, your passengers, as well as others on the road.
SEE ALSO:WAYS TO REPAIR AIR BRAKES