Mercedes-Benz W123 brake bleeding
How do I bleed the brakes on a Mercedes-Benz W123, and in what order?
1. Fill the brake fluid reservoir to the brim and keep it full the whole time. 2. Start from the wheel with the longest brake line (right rear wheel) and work towards the shortest. 3. Press the pedal slowly and always close the bleed screw before lifting your foot off the pedal. 4. Bleeding is done when the pedal feels firm and no bubbles are seen in the clear hose. Brakes are safety-critical: have a workshop check the result.
Why does the W123 brake pedal sink to the floor after bleeding?
There is still air in the lines or the reservoir has been allowed to run empty. Fill the reservoir to the brim, because the front and rear circuits each have their own part and the fluid drops quickly on the rear circuit side. Bleed again until the pedal no longer sinks to the floor. If the fault continues, have a workshop check the brakes.
How do I loosen a brake caliper bleed screw that has rusted solid?
Spray rust remover on the screw days before the job. A left-hand extractor should not be used, because it can split the caliper. If the screw breaks or does not come out, let a workshop deal with it. Brakes are safety-critical, so have the result checked.