🚗 Classic Fault — Mercedes-Benz W115 (1968–1976)
Sill (rocker panel) rust — structural concern
💰 Estimated Repair Cost
$200 – $800 USD
Parts and labour estimate
🔧 Tools Required
Angle grinder, welder or professional, chassis protection wax
📋 Overview
Rust in the sill sections below the doors. This is the most common structural issue on the W115. Water collects inside the box-section sills and cannot drain, causing rust from the inside out.
🩺 Symptoms
- Bubbling or flaking paint on sill lower edges
- soft spots when pressing sill
- rust holes visible from below
- jacking point failure
🔍 Possible Causes
- Water ingress into hollow sill section
- blocked or absent drainage holes
- original underseal trapping moisture
- accumulated road salt
🛠️ Diagnosis Steps
- Check sills by pressing firmly — any flex indicates rust.
- Inspect from below with torch.
- Check jacking point integrity before lifting.
- Minor rust: treat and seal.
- Serious rust: professional welding required.
✅ Most Confirmed Fix
Cut out rusted sections. Weld in new steel repair panels. Apply cavity wax injection. Underseal exterior.
60% of users confirm this fix worked (5 reports)
🏷️ Parts Needed
Sill repair panel set; rust converter; cavity wax
🔗 Other Mercedes-Benz W115 Faults
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