More of a concern is the Vanos variable valve timing unit, with one on each bank of cylinders. It's very common for them to make a rattling noise when the engine is started from cold, but this should soon quieten down. It's noisy on start-up as oil drains out when the car is parked. If noise persists when the engine is warmed through, it will require a new or rebuilt Vanos unit. This need not be the wallet-breaking event some will have you believe as the Vanos unit can be rebuilt, either just with new seals or completely refurbished by a specialist such as Mr Vanos. The worst thing to do it ignore any noises from the Vanos unit when the engine is warm as a complete failure can wreck the engine and land you with a £6,000 bill to fit a new motor.
E39 M5. When it fails, the engine will go into a limp mode or stop altogether. Sometimes switching off and restarting the car will be enough to get you home, but new MAFs will be needed and cost from around £70 each from specialists plus labour to fit. From BMW, MAFs are £580 apiece.
Another reason for the engine going into emergency mode are faulty throttle valve potentiometers, though the design was improved in August 1999 and any car that had this problem should have been dealt with by now.
Dan Norris of Munich Legends says: "Unlike an E46 M3 where most of the problems will be visible, you must put a diagnostic tool on the E39 M5 as most of the big concerns are hidden within the engine. Failed MAFs can go unnoticed as the car feels quick to the owner and they deteriorate gradually. You also need to make sure the lambda sensor is working."
A clutch can last up to 100,000 miles if the car spends most of its time on the motorway, but a more realistic average mileage is around the 60,000-mile mark. The six-speed manual gearbox from Getrag is more than up to the job, though a notchy shift action when cold is a characteristic.
Some owners remove the rear-most exhaust silencer to improve the sound of the car with no detriment to power or emissions. A more comprehensive Eisenmann or Hayward and Scott exhaust system will set you back from around £1,500.
"While the M5 is meant to be a discreet car there is no denying the exhaust is too quiet, which is why many people go for the option of a 'silencer delete'."