"What are the common issues with the M30 engine in this model?"

Question

Accepted Answer

The M30 engine in the 1986 BMW 635CSi (E24) is reliable but has known issues:

1. **Oil Consumption**
   - Common due to worn piston rings/valve seals. Your vehicle had recent oil changes (March 2025) but high mileage (112k+ miles) increases risk.

2. **Timing Chain/Tensioner Wear**
   - Stretching/failure can cause misfires. No recent work noted; listen for rhythmic "ticking".

3. **Cooling System Vulnerabilities**
   - Weak water pumps/thermostats. Coolant hose replaced (March 2022) is good, but inspect other components.

4. **Main Bearing Wear**
   - Knocking noises at startup may indicate wear. High mileage increases risk.

5. **Fuel Delivery Issues**
   - Degraded injectors/pump. No recent work noted; test if power loss occurs.

**Recommendations**: Regular maintenance, monitor for symptoms, and refer to [Bimmerforums E24 Thread](https://www.bimmerforums.com/forum/showthread.php?2397628-E24-89-635csi-PROBLEMS) and [M30 Engine Review](https://enginecrux.com/the-bmw-m30-engine-specs-problems-and-reliability/) for deeper insights.

Lot 2899-DFW: 1986 BMW 635CSi

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Lot 2899-DFW: 1986 BMW 635CSi

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