BMW 320i
Light-alloy straight-six with DOHC and variable camshaft timing. Smooth and rev-happy; susceptible to Nikasil issues on early examples.
Six-cylinder base
Inline-six with a good gait — underpowered for the heavy 5 Series though.
Engine Weaknesses 5
The DISA variable intake valve breaks at the pivot base or the membrane tears. Fragments can be sucked into the engine and cause total damage.
Symptoms: Power loss in the lower rev range, rattling or clattering from the intake area, in the worst case engine damage from ingested fragments.
The electric coolant thermostat from Behr/Mahle fails prematurely. BMW recommends only original thermostats. Failure leads to overheating or permanently cold running.
Symptoms: Engine fails to reach operating temperature or overheats, heater works poorly, increased fuel consumption with permanently cold running.
The plastic thermostat housing of the M52B20 warps through thermal stress. Coolant loss at the housing is a known wear pattern at mileages above 120,000 km.
Symptoms: Coolant patch under the car, engine warms up poorly or overheats, coolant level drops without visible leaks at hoses
The differential pressure valve of the crankcase ventilation tears or sticks, the drain hose blocks. Oil enters the intake, the mixture deteriorates, oil consumption rises.
Symptoms: Oil film in air filter housing, rough idle, slight oil consumption, oil smell in cabin with engine off
The square gasket between oil filter housing and engine block fails frequently. BMW part number 11421719855 — aftermarket gaskets typically last shorter in practice.
Symptoms: Oil leaking from the side of the engine below the oil filter, oil smell with hot engine, oil patches under the vehicle.
Vehicle Weaknesses 7
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.
Plastic sliders, motor brushes, and window regulator connectors fail frequently. BMW doesn't supply individual parts — only complete regulator mechanisms.