No brakes, pedal goes to the floor

WHYTEZ97

MEMBER
1993 FORD EXPLORER
4.0L
V6
4WD
AUTOMATIC
133,000 MILES

Driving home yesterday brakes went out completely, couldn't even get pressure pumping brakes with engine off. Replaced master cylinder now I get pressure when pumping with engine off, but as soon as I start the engine the pedal drops.

Saturday, March 13th, 2021 AT 3:02 PM

1 Reply

ASEMASTER6371

MECHANIC
52,797 POSTS

Good afternoon,

This sounds like you have air trapped in the system.

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

If you have ABS, I attached the procedure below. If you do not, you may need to rent a pressure bleeder to force out the air from the lines. If you have ABS, you will need a scan tool to open the valves in the control unit to get the air out.

Roy

Perform this procedure only if the hydraulic control unit (HCU) has been replaced.
1. Perform conventional brake system bleed procedure.
2. Connect bleeder box tool No. T90T-50-ALA and brake jumper cable tool No. T93T-50-ALA or equivalents.
3. Press down on brake pedal and depress ``VALVES'' button on bleeder box. Pedal will fall.
4. Release ``VALVES'' button, then release the brake pedal.
5. Repeat steps 3 and 4.
6. Depress ``MOTOR START'' button and let pump motor run for 1 minute.
7. Perform conventional brake system bleed procedure.