Monday, June 20, 2011

How to remove Brake Booster on the car?

Do you hear a hissing sound under the dash when you push the brake pedal? Does your pedal go down and not stop the car? Yep, the diaphragm in your booster is torn and you will have to replace the booster. Here is the quick and dirty on this job.
There are a couple of warnings to give you up front. You may need line wrenches to loosen the hydraulic fittings on the master cylinder. A line wrench is like a box end wrench with a cut in it to fit over a line. Using open end wrenches can result in a stripped fitting. And never use a vice grip on a line fitting, unless you plan to replace both the line and the fitting. The second warning is on brake fluid. It is corrosive, so don't get it on your paint, and make sure you clean it up.
Now for the procedure. I always try to do it without disconnecting the brake lines from the master cylinder, if possible. Below is a picture of a typical master cylinder and booster.

In this case, they routed the A/C evaporator lines right in front of the master cylinder, so we'll never get this booster out without removing the master cylinder. Remove the nuts holding the master cylinder and also the cable from the reservoir level sensor. One nut is visible in the upper right of the pic below. The sensor cable is right thru the middle of the pic, and one of the hydraulic fittings is on the left.

Here the cable is removed revealing the other hydraulic fitting.

If the pushrod is loose, remove it and set aside. Pull the master cylinder forward off the studs. See if you can push it down such that the booster will clear it coming off. Just be careful not to kink the hydraulic lines. Remove the vacuum line from the booster--it should pull straight out. A pic of the vacuum connection is below. You can also see the other nut holding the master cylinder onto the booster.

Go under the dash and remove the 4 nuts holding the booster. Check for and remove any pin that may hold the booster pushrod to the brake arm. Back under the hood, pull the booster forward and see if it will clear the master cylinder. If not, have the new booster ready to go in, remove the lines using line wrenches, remove the master cylinder and turn it so as to keep the fluid from leaking out of the ports. Set it down and swap out the boosters. Quickly get the maser cylinder back in and the lines connected. Don't forget the pushrod if you took it out, and make sure it's properly resting in the push recesses. Tighten the lines just until they stop leaking. Replace the booster nuts and pin you may have removed--tighten the nuts. Also tighten the master cylinder nuts and reconnect the sensor cable. Now, if you had to remove the master cylinder, have an assistant help you bleed it at the fittings. Have them pump and hold the brake pedal down while you loosen and then re-tighten the fittings one at a time. If any air comes out, repeat on that fitting until only oil comes out. Clean up any fluid and test drive the car. If the brakes are soft, you may have to bleed the brakes at the wheels to get any remaining air out of the system.

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