🚗 Classic Fault — Mercedes-Benz W115 (1968–1976)
Coolant corrosion from neglected antifreeze changes
💰 Estimated Repair Cost
$20 – $50 USD
Parts and labour estimate
🔧 Tools Required
Basic tools
📋 Overview
When antifreeze is not changed every 2 years, corrosion inhibitors deplete and the coolant attacks aluminium and cast iron, producing brown sludge that restricts flow throughout the system.
🩺 Symptoms
- Brown sludge visible in coolant
- restricted flow
- gradual overheating tendency
- blocked heater matrix
🔍 Possible Causes
- Neglected coolant changes
- wrong antifreeze type mixed
- plain water used
🛠️ Diagnosis Steps
Remove radiator cap. Inspect coolant colour — should be green or blue, not brown.
✅ Most Confirmed Fix
Flush system with specialist flush compound. Refill with 50/50 antifreeze and distilled water.
83% of users confirm this fix worked (25 reports)
🏷️ Parts Needed
Coolant flush solution; antifreeze; distilled water
🔗 Other Mercedes-Benz W115 Faults
Own a Mercedes-Benz W115?
Share your experience with this fault — or report a different issue. Your knowledge helps other classic car owners worldwide.