ninaberger10
B Klasse Diesel Spongy Brake Pedal
Summary of the thread
A 2005 Mercedes B Klasse diesel is experiencing a spongy brake pedal. Initial checks of the brake fluid showed no issues, leading to questions about potential electrical problems or brake pad wear. Suggestions included inspecting brake lines for leaks, as air in the system can cause a spongy feel. Ultimately, a professional diagnosis revealed the issue was with the ABS module malfunctioning due to undervoltage, which was resolved by a mechanic.
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4 comment(s)
ninaberger10 (community.author)
I have not inspected the brake lines directly, as that would require more sophisticated tools, but I did not notice any visible leaks around the calipers or master cylinder. Could a minor leak truly manifest in such a pronounced change in pedal feel? I am reluctant to start replacing parts without more certainty.
robinhahn7
A minor leak can definitely cause that. Air in the lines is a pain. But if you're not seeing anything obvious, and you suspect undervoltage, it might be best to have the system properly diagnosed at a workshop. They can check the ABS module and other components that rely on consistent voltage. It's better than chasing ghosts and potentially making things worse.
ninaberger10 (community.author)
I appreciate the advice. I shall schedule an appointment with a trusted mechanic to perform a comprehensive evaluation of the brake system, including the ABS module and the brake lines. It turned out it was indeed the ABS module. The undervoltage caused the ABS to malfunction. Repair cost me 240€
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MERCEDES
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BKLASSE
robinhahn7
I had a similar issue with my B Klasse. The strange pedal feel, especially. It turned out to be a combination of things. Have you checked the condition of your brake lines? Sometimes a small leak can introduce air into the brake system, leading to that spongy feeling. It's worth a look before you start tearing things apart.