🚗 Classic Fault — Mercedes-Benz W115 (1968–1976)
Carb balance pipe hose perished causing vacuum leak
💰 Estimated Repair Cost
$10 – $30 USD
Parts and labour estimate
🔧 Tools Required
Hose clamp tools
📋 Overview
A rubber hose connects the two Zenith carburetors as a balance pipe. This hose perishes and cracks over time, creating a vacuum leak that makes synchronization impossible and causes rough running.
🩺 Symptoms
- High idle that cannot be controlled
- rough running
- synchronization impossible
- hissing sound between carbs
🔍 Possible Causes
- Perished balance pipe hose
- cracked hose joiners
🛠️ Diagnosis Steps
Inspect balance pipe hose and fittings visually. Spray carb cleaner on hose while idling.
✅ Most Confirmed Fix
Replace balance pipe hose and any perished fittings.
89% of users confirm this fix worked (36 reports)
🏷️ Parts Needed
Balance pipe hose and fittings
🔗 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.