🚗 Classic Fault — BMW (1982–1994)
E30 325i M20 head gasket failure at high mileage
💰 Estimated Repair Cost
$200 – $600 GBP
Parts and labour estimate
🔧 Tools Required
Combustion leak tester, torque wrench, head gasket set
📋 Overview
High-mileage M20B25 engines suffer head gasket failure between cylinders 5 and 6, or at the water jacket.
🩺 Symptoms
- Coolant loss with no external leak
- white exhaust smoke
- rough running on cylinders 5/6
- mayo under oil cap
🔍 Possible Causes
- Blown head gasket
- cracked head from previous overheat
- warped head surface
🛠️ Diagnosis Steps
- Combustion leak test kit in coolant
- check for pressure in coolant when engine running
- oil analysis for coolant
✅ Most Confirmed Fix
Head gasket replacement with head skim
78% of users confirm this fix worked (26 reports)
🩺 Related Symptoms
🌡️ Coolant in oil — mayonnaise under cap
🌡️ Coolant loss with no visible leak
🔩 White smoke from exhaust
🔗 Other BMW Faults
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