BMW 316i

Plastic thermostat housing and coolant hoses become brittle with increasing age. Thermostat failure leads to overheating, cracked hoses to sudden coolant loss.

Symptoms: Engine warms up slowly or overheats, coolant loss without visible leak, coolant level drops regularly.

The timing cover gasket is the most common source of oil loss on the M43. Repair usually requires cylinder head removal, which significantly increases the work involved. Typical from 150,000 km.

Symptoms: Oil patches under the engine, oily smell in engine bay, visible deposits on the front of the engine block

Plastic coolant flanges on the cylinder head become porous with age and start to leak. Known weak point of the M43 engine family — recommended to replace all flanges simultaneously as a preventive measure.

Symptoms: Coolant loss without visible puddle, coolant smell after driving, dropping coolant level

The cast rear trailing arms (swing arms) of the E36 rear axle are prone to corrosion and pitting near the spring seat. When severely affected the trailing arm must be replaced.

The viscous fan coupling loses its silicone oil over time and can no longer couple the engine fan adequately. In traffic or at low speeds, engine temperature rises rapidly into the red zone.

The rubber-metal barrel bearings (Tonnenlager) of the rear axle become porous and separate. Repair requires special tools and full rear axle disassembly. MOT-relevant when heavily worn.

Sills rust through almost universally — especially through blocked drain holes. Wheel arches rust from the inside along the flange joint, only visible once damage is already severe.

Water pump and thermostat are wear items. A faulty thermostat causes permanent under- or overheating; a failed water pump leads to coolant loss and engine damage.

The alternator voltage regulator and the EWS electronic immobiliser are classic weak points. The voltage regulator fails most often, rarely the whole unit. EWS can cause intermittent start failures.