Questions and Answers

Mercedes Benz 190E Master Cylinder Q. I installed a new master cylinder in a 1987 Mercedes Benz 190E, 2.3 liter. Having trouble with bleeding procedure. I bench bled the master cylinder, filled the brake lines from the bottom up with oil can pump filled with brake fluid, but I haven't been able to hold the prime in the master cylinder to the front wheels. What can I do to keep the prime while attaching the brake lines to the master cylinder? Guthrie

A. Well, the proper way to bench bleed the master cylinder is to clamp it in a vice and hook up the plastic bleeding fittings and hoses. Most master cylinders come with these. If yours didn't you can pick up a set at an auto parts store for cheap.

Install the plastic fittings into the master cylinder and loop the hoses into the master cylinder reservoir. Fill the reservoir with brake fluid. Now pump the master cylinder until no more bubbles come out of the hoses.

Tie a knot in the hoses to hold the brake fluid in while you install it in the car. Take off the plastic fittings and hook up the lines. If you leave the master cylinder attaching nuts loose, it will make attaching the lines easier.

Once the lines are fitted, tighten the attaching bolts and the lines. Now you do a final bleed of the master cylinder by pumping the pedal and cracking the lines (or bleeders if equipped) on the master cylinder to be sure there is no more air.