🚗 Classic Fault — Mercedes-Benz W115 (1968–1976)
HT leads deteriorated — arcing to engine block
💰 Estimated Repair Cost
$25 – $60 USD
Parts and labour estimate
🔧 Tools Required
None for diagnosis
📋 Overview
Original rubber HT leads crack with age allowing high voltage to arc to nearby metal rather than reaching the spark plug. Most common in damp conditions.
🩺 Symptoms
- Misfiring in wet or damp conditions
- visible spark jumping from lead to block in the dark
- specific cylinder miss
🔍 Possible Causes
- Cracked or perished HT lead insulation
- leads touching hot surfaces
🛠️ Diagnosis Steps
Run engine in dark garage. Look for sparks jumping from leads. Any visible arcing confirms replacement needed.
✅ Most Confirmed Fix
Replace complete HT lead set with silicone leads.
93% of users confirm this fix worked (51 reports)
🏷️ Parts Needed
HT lead set for M115 — silicone recommended
🔗 Other Mercedes-Benz W115 Faults
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