🚗 Classic Fault — BMW (1982–1994)
E30 M20 cooling system failure — plastic impeller disintegration
💰 Estimated Repair Cost
$40 – $120 GBP
Parts and labour estimate
🔧 Tools Required
Coolant drain tools, torque wrench
📋 Overview
The M20 and M40 water pump uses a plastic impeller that disintegrates with age, causing sudden loss of coolant circulation.
🩺 Symptoms
- Sudden overheating with no warning
- coolant temperature spikes rapidly
- coolant level normal
- no external leak
🔍 Possible Causes
- Disintegrated plastic water pump impeller
- failed thermostat
- cracked head from previous overheat
🛠️ Diagnosis Steps
Remove water pump and inspect impeller — if blades are missing or loose, pump has failed internally
✅ Most Confirmed Fix
Water pump replacement — use metal impeller pump
90% of users confirm this fix worked (44 reports)
🩺 Related Symptoms
🔗 Other BMW Faults
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