BMW 640d N57 Diesel and 650i N63 V8

There is something quietly absurd about a grand tourer that will pull from low revs in near silence, waft you from Auckland to Hamilton without breaking a sweat, then remind you on the way home that 313 horsepower and 630 Newton metres is not, in fact, a frugal commuter. The N57 straight six diesel is one of the finest engines BMW has produced. It is smooth, torquey, and genuinely capable. But it has its habits, and after a few years and a good slug of kilometres, those habits start showing up in predictable places.

The swirl flap situation is worth a special mention. When a flap or its linkage fails, pieces can be ingested into the engine. Catching wear early, either through a scope inspection or by reading the correct live data, saves you from a far more expensive repair down the track. This is exactly where having the right diagnostic platform matters.

We run BMW ISTA Rheingold through a genuine ICOM NEXT interface on these cars. That is the factory diagnostic platform, not a generic OBD reader. It reads the real N57 data correctly, allows proper fault code interpretation, and lets us carry out coding and module programming where needed. A generic scan tool simply does not give you the full picture on these systems.

On the emissions side, the DPF and EGR on the 640d need legitimate attention rather than being ignored. If the car has mostly done short trips, a forced regeneration cycle and a proper inspection of the EGR cooler condition should be on the list. We handle DPF and EGR system cleaning and repair as a proper diagnosis first process, not a workaround.

Routine servicing on the 640d covers more ground than just an oil change. A proper service schedule includes engine oil and filter with the correct BMW approved diesel grade, air filter, fuel filter and cabin filter replacement, drive belts and wipers, glow plug inspection and replacement as needed, brake pads, rotors and sensor replacement, timing chain condition assessment, DPF and EGR cleaning or replacement where required, AdBlue system service where fitted, and suspension checks and repairs.

The 640d also responds very well to a Stage 1 tune once it is in good mechanical health. We can take the stock 313 horsepower and 630 Newton metres up to 365 horsepower and 730 Newton metres, a gain of 52 horsepower and 100 Newton metres from the ECU alone. That is a meaningful change in a grand tourer that already had excellent torque, and it transforms the motorway overtaking ability without touching the hardware.

If the 640d is the composed, torquey long distance runner, the 650i is the car for when you want all eight cylinders doing exactly what they were born to do. Twin turbos, 407 horsepower, 600 Newton metres, and a sound that the diesel simply cannot match. It is a serious machine. It also has an engine, the N63 twin turbo V8, that BMW itself covered under a Customer Care campaign. That tells you something about the known weak points, and it means any 650i you are looking at deserves a thorough inspection before purchase and a disciplined service history going forward.

Where the 640d's issues are mostly manageable diesel wear items, the 650i's N63 adds a layer of complexity specific to its hot vee architecture. The turbos sit in the valley between the cylinder banks, and that area runs hot. Heat is the enemy of the wiring, seals and injectors in that region.

The timing chain situation on the N63 is not something to defer. Guide wear allows the chain to jump or skip under load, and the consequences are serious. If a 650i you own or are buying has not had the chain and guides inspected or replaced at appropriate mileage, that needs to go to the top of the list.

Valve stem seal leaks are another item that can creep up gradually. A small amount of smoke on a cold start that clears quickly can turn into a more persistent consumption issue if left alone. The correct approach is a proper diagnosis before committing to the repair, which is exactly what our ISTA based process delivers. We use BMW ISTA Rheingold through a genuine ICOM or ICOM NEXT interface on the 650i, the same factory platform that gives us proper live data from the V8, allows full coding and module programming, and reads fault codes the way BMW intended them to be read.

Compare this to the 640d and you can see the difference in character. The diesel's issues are mostly predictable wear items on a fundamentally tough unit. The N63 petrol has a higher ceiling and a higher floor when it comes to potential repairs. Valve stem seals and timing chains are not cheap jobs. That said, a well maintained 650i with a solid service history and a documented chain inspection is a genuinely rewarding car to own.

A full service on the 650i covers both banks and goes deeper than a standard oil change: engine oil and filter with the correct BMW LL-01 grade, air filters for both cylinder banks, cabin filter, fuel filter and wipers, spark plugs and ignition coils checked per bank, drive belts and coolant and thermostat service, brake pads and rotors on the M Sport setup, valve stem seal inspection and replacement where needed, timing chain and guide assessment, injector health check, and air suspension or shock inspection where fitted.

The N63 also responds very well to a Stage 1 tune, but only once the engine is confirmed healthy. Pushing more boost through an engine with a marginal chain or tired seals is not the right order of operations. Sort the mechanicals first, then we can take the stock 407 horsepower and 600 Newton metres to 470 horsepower and 700 Newton metres, a gain of 63 horsepower and 100 Newton metres from the ECU calibration alone. That is a substantial step up, and on a grand tourer of this size and weight, it is very much felt.