Free Car Repair Advice by Certified ASE Technicians
Troubleshooting
/ Brake Pedal
on Floor
Brake Pedal Goes to the Floor
Troubleshooting Procedure
A. Check the Brake System Fluid Level - Check the level of fluid in the
brake master cylinder. It is natural for fluid to be a low if the front or rear
brake pads/shoes have worn down, but if they are in good condition and the brake
master cylinder
reservoir is empty you might have a brake fluid leak somewhere in the system.
Inspect
front brake calipers,
rear
wheel cylinders (drums) or
rear
brake calipers and flex hoses front and rear of vehicle and look for any sign
of fluid leakage. Also check the rear of the brake master cylinder for fluid leaks,
if brake fluid is present the master cylinder seals have failed and the
master cylinder
needs to be replaced. Replace any parts that are leaking or show signs of previous
leakage. Refill and bleed the brake system as needed. (Note: if brake fluid has
contacted the brake components i.e.
brake pads or
brake shoes the brake lining material is contaminated and must be replaced)
If the brake fluid in the reservoir is full proceed to the next step.
Brake Master Cylinder
B. Brake Master Cylinder is Full of Brake Fluid - If upon inspection
the brake
master cylinder
is full of fluid, the brake master cylinder may be bypassing internally. This
means the seals inside the
master
cylinder have failed allowing the fluid from the front of the master cylinder
plunger to slip through to the rear of the plunger and back into the fluid reservoir.
Allowing the brake pedal to go to the floor with out pressurizing brake fluid into the
system. Replace
master cylinder
with new unit and bleed system as needed.
C. Failing Axle Bearings - The vehicle
axle bearing
holds the wheel true to the axle shaft while allowing the wheel to rotate. If the
bearing fails it will allow the rotor to move back and forth, forcing the
brake pads inward into the caliper. Then as you apply the brake
pedal it will
go to the floor as the caliper fills with fluid. In this case it may take one or
two pumps to the brake pedal to regain normal operation. Inspect and replace failed
axle bearings as needed, finish by bleeding and adjusting the system.
D. Air in Brake System - When
brake calipers or
rear
wheel cylinders fail they can allow air into the system when the brake pedal
is released. Bleed the brake system by loosening the air bleeder, if air is observed
from the bleeder replace the caliper or wheel cylinder and re-bleed system. This
condition is rare but it does happen.
For exact specific repair procedures for any of the steps above visit our
online repair
manual page.
Troubleshooting
/
Brake Pedal
on Floor
Check Manufacturer Specific Brake
Pedal Questions and Answers
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