🚗 Classic Fault — Mercedes-Benz W115 (1968–1976)
Oil pressure relief valve sticking — abnormal pressure
💰 Estimated Repair Cost
$30 – $200 USD
Parts and labour estimate
🔧 Tools Required
Mechanical oil pressure gauge, basic tools
📋 Overview
The M115 oil pressure relief valve can stick in closed or open position causing dangerously high or low oil pressure. Unusual gauge readings should be investigated immediately.
🩺 Symptoms
- Very high or very low oil pressure reading
- oil leaks from seals suddenly
- oil pressure light flickering
🔍 Possible Causes
- Stuck oil pressure relief valve
- failed oil pump
- blocked oil strainer
🛠️ Diagnosis Steps
Compare oil pressure gauge to specification: 3.0-3.5 bar at 3000 RPM warm. Test with mechanical gauge to confirm sender accuracy.
✅ Most Confirmed Fix
Clean and free relief valve. Replace spring if fatigued. Replace pump if worn.
72% of users confirm this fix worked (15 reports)
🏷️ Parts Needed
Oil pressure relief valve spring and ball; oil pump
🔗 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.