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Originally Posted by cnm
I finally received my replacement brake booster and I have a few questions from the directions on how to remove and install a brake booster from the W108 service manual. I understand how to remove the booster itself. However, I am having trouble with the directions regarding draining the compensating tank and bleeding the brake lines.
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"Compensating tank" means the brake fluid reservoir that is on top of the master cylinder. I've never heard that term before - is your shop manual British?
Quote:
Originally Posted by cnm
Step 2 states "pump compensating tank of master cylinder empty via an opened bleeding plug of the front axle and rear axle brake circuit. Then loosen brake lines of tandem master cylinder." I do not know what this step refers to, specifically what and where is the bleeding plug (not shown in the diagrams) or how to pump the compensating tank empty.
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Basically the instructions want you to get the fluid out of the reservoir. Each brake caliper will have a brake bleeding valve. The reservoir will likely have a compartment that is for the front brakes and a compartment for the rear brakes. So if you open a front bleed valve and push a tube over it so it can drain into a jar or something, and you pump the brakes, it will pump all of the fluid out of the reservoir. Same for the rear brakes. Tandem master cylinder means that there is a pressure line that goes to the front brakes and a pressure line that goes to the rear brakes. This also could be called "duel circuit brakes".
After you have pumped the fluid out of the reservoir it's telling you to remove the hydraulic lines from the master cylinder. They want you to empty the fluid first because otherwise it will just make a big mess when you remove the hydraulic lines.
Quote:
Originally Posted by cnm
Finally, the last few steps (13 and 15) state that I "reconnect the brake lines," "bleed the brake system and check for leaks." Do I not refill the compensating tank at any time? I didn't see a step for this. Also, not sure how to bleed the brake lines.
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You need a tutorial on brake bleeding. Try googling it. It's not mercedes-specific, but google brake bleeding and do some reading and then come back. It's not difficult and it is easier with two people. Basically you are bleeding all of the air out of the brake lines. You keep topping off the reservoir and keep pumping more fluid through the system and out the bleed valves until there are no air bubbles left in the system. And you do this starting at the farthest point from the master cylinder and working your way towards the closest point (closest wheel).