Cooling & lubrication
Accessory-belt tensioner
Keeps suitable tension on the accessory belt.
On the external accessory drive.
A loaded pulley compensates for belt movement and length variation within its design range.
A spring-loaded hand maintaining a taut rope.
Belt flutter, noise or misalignment can involve the tensioner and adjoining pulleys.
Fluids use vehicle-specific schedules. Seals, pumps and heat exchangers depend on age, condition and operating history.
Simple seals and filters can be accessible; an integrated pump, buried housing or overheating damage can make repairs more involved.
A noisy BMW belt drive needs the whole pulley path checked rather than a belt alone.
BMW combustion models; additional coolant circuits also appear in hybrids and electric BMWs.
Same system