Why Do I Have to Pump My Brakes Before I Get Enough Pressure to Stop After I Just Changed My Brakes?

Bleed brakes if necessary for a firm pedal.

Having a soft brake pedal after changing your brakes is usually the result of somehow getting air in the brake lines. For instance, if you opened the bleeder screws on the calipers to compress them, air may have entered. Replacing a caliper or wheel cylinder also introduces air into the system. The resulting problem is that when you apply the brakes, the air in the system is compressed instead of the brake fluid, and you pedal soft. Bleeding your brakes should fix the problem.

Things You'll Need

• Wheel chocks
• Jack
• Jack stands
• An assistant
• Safety glasses
• Wrench set with box-ends
• 3/16 clear tubing, 3 feet long
• Plastic water bottle, clean and dry
• Fresh brake fluid

Instructions

1. Park the vehicle on a level, paved surface. Place wheel chocks in front of the front wheels. Raise the rear of the vehicle with a jack and support with jack stands.

2. Open the master cylinder and make sure it is full. If necessary, top off with fresh brake fluid -- check the owner's manual to find what fluid the vehicle requires. Cover the top of the master cylinder with a clean, dry shop rag.

3. Put on a pair of safety glasses and begin bleeding the wheel cylinders, or calipers at the passenger side rear wheel. Attach a box-end wrench to the bleeder screw. Attach a piece of 3/16 inch clear tubing to the nipple on the bleeder screw. Fill a clear water bottle – it must be dry – about 1/3 of the way with clean brake fluid. Place the end of the plastic tubing in the bottle so it is submerged in the fluid.

4. Ask an assistant to push the brake pedal three times and hold it down on the last push, and not to let up on the pedal until you say to. Open the bleeder screw by turning it counterclockwise with the box wrench. Brake fluid and possibly air bubbles will move through the tubing. As soon as the flow of fluid slows, close the bleeder screw. Tell your assistant to let up on the pedal and pump it again. Open the bleeder and look for bubbles. Close the bleeder. Repeat one more time.

5. Check the fluid level in the master cylinder and refill. Every time you open a bleeder, the fluid level in the master cylinder will drop. Do not empty the master cylinder or you will have air in it and have to start over.

6. Move to the driver side rear wheel and repeat the process. You will probably see some improvement at this time.

7. Raise the rear of the vehicle, remove the jack stands and lower it to the ground. Place wheel chocks behind the rear wheels. Move to the front of the vehicle, raise it with a jack and support with jack stands.

8. Repeat the bleeding process starting with the passenger side and finishing with the driver side wheel. Lower the vehicle; make sure the master cylinder is full. Replace the cap.

Tips & Warnings

• If you have ABS brakes and your pedal does not firm up, you should take the vehicle to a shop or dealership to have the ABS system bled or reset.

• Only add fresh brake fluid to the master cylinder.

• Brake fluid will attack paint. If you get it on a painted surface, immediately wash with soap and water.

• Wash any exposed skin with soap and water. If you get it in your eyes, flush with water and seek medical attention.

References

• Chilton's Ford Mercury Lincoln Mid-Size 1971 through 1985; Chilton Book Company
• Zeckhausen Racing: How to Bleed Brakes