🚗 Classic Fault — Mercedes-Benz W115 (1968–1976)
Radiator drain tap seized — coolant change impossible
💰 Estimated Repair Cost
$15 – $40 USD
Parts and labour estimate
🔧 Tools Required
Pliers, penetrating oil, thread sealant
📋 Overview
The brass radiator drain tap corrodes and seizes in the closed position. This means the cooling system cannot be properly drained for antifreeze changes, leading to progressively weaker antifreeze and internal corrosion.
🩺 Symptoms
- Cannot drain coolant properly
- tap will not turn
- coolant not changed due to inaccessible drain
🔍 Possible Causes
- Corroded brass drain tap
- lime scale build-up
🛠️ Diagnosis Steps
Attempt to turn tap with pliers — does not move confirms corrosion.
✅ Most Confirmed Fix
Soak with penetrating oil. Replace drain tap. Consider blanking plug and draining via hose.
80% of users confirm this fix worked (20 reports)
🔗 Other Mercedes-Benz W115 Faults
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