🚗 Classic Fault — Mercedes-Benz W115 (1968–1976)
Radiator cap seal failure — coolant loss at pressure
💰 Estimated Repair Cost
$10 – $20 USD
Parts and labour estimate
🔧 Tools Required
Radiator cap pressure tester
📋 Overview
The radiator cap seal deteriorates and fails to hold system pressure (0.9 bar). Low pressure reduces the coolant boiling point, causing overheating at lower temperatures than expected.
🩺 Symptoms
- Coolant loss via overflow
- boils at lower temperature than normal
- hoses collapse when cold
🔍 Possible Causes
- Failed radiator cap seal
- incorrect pressure rating cap fitted
🛠️ Diagnosis Steps
Test cap with pressure tester. Should hold to stated pressure.
✅ Most Confirmed Fix
Replace radiator cap. Ensure correct pressure rating 0.9 bar.
90% of users confirm this fix worked (44 reports)
🏷️ Parts Needed
Radiator cap — 0.9 bar
🔗 Other Mercedes-Benz W115 Faults
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