What to Do about Mushy Brakes

January 27, 2012

Mushy brakes can be a very scary problem as it can cause difficult braking, especially in an emergency situation. This article will outline some of the main causes of mushy brakes and how to diagnose them.

Step One: Check Brake Fluid Level

  • First, open the hood
  • Next, locate the brake master cylinder
  • Then, remove the cap and look at the level of the fluid inside
  • Finally, if fluid is low, add fluid and recheck brakes

Step Two: Check for Air in the Lines

  • First, have a fried pump. Pump the brakes until pedal is firm
  • Then, while holding the pedal, open the bleeder valve
  • Next, if any air comes out, perform a complete bleed
  • Finally, perform this task on all four bleeder valves

Step Three: Check for Fluid Leaks

  • First, check master cylinder for leaking fluid from back
  • Next, check all lines under the hood for leakage
  • Then, jack up the vehicle and look underneath for leakage
  • Finally, if leakage is found, repair and recheck brakes

Step Four: Check Brake Pads and Shoes

  • First, remove front wheels
  • Next, visually inspect front brake pads for excessive wear
  • Then, remove rear wheels
  • Next, visually inspect rear pads for excessive wear
  • Finally, if any excessive wear is found, replace pads and retest the brakes

Step Five:  Check Calipers for Leakage

  • First, remove the front wheels
  • Next, remove the front calipers
  • Then, inspect around the caliper piston for leakage
  • Finally, if leakage is found, replace caliper or rebuild caliper

Step Six: Check Wheel Cylinders for Leakage

  • First, remove rear wheels
  • Next, Remove rear brake drums
  • Then, pull dust boot from wheel cylinders
  • Finally, if fluid is leaking inside the dust boot, replace the wheel cylinders

Step Seven: Check Proportioning Valve for Proper Distribution

  • First, open all four bleeder valves
  • Next, place a container by each bleeder valve to catch fluid
  • Then, press brake pad slowly until pedal is on the floor
  • Then, check the level in each container
  • Finally, if one or more of the containers has drastically less fluid, replace the valve

 Step Eight: Check Brake Booster for Vacuum Leak

  • First, locate the brake booster under the hood
  • Next, inspect all vacuum lines from booster for vacuum leaks
  • Then, Check the booster itself for vacuum leaks, a hissing sound is a tell tail sign
  • Finally , if any leaks are present, repair them and recheck brakes

Step Nine: Bench Check the Master Cylinder for Proper Operation

  • First, remove the master cylinder from the vehicle
  • Then, perform a bench test by using a bench bleeder on the master cylinder
  • Next, read the pressures coming out of the brake lines from the master cylinder
  • Then, allow the master cylinder to sit for several hours and return to read the pressure remaining
  • Finally, if the pressure does not remain or the pressure never builds up, replace the master cylinder

There are many causes to mushy brakes. This article only outlined the main causes. Sometimes, there are multiple causes to mushy brakes as well, so be certain to recheck the brakes after every repair is completed. Now that you have the basic outline, get to work diagnosing that mushy brake pedal.

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