This big coupé has style, but what’s it like under the skin?
The shark-nosed 6-Series looks good from the outside, but it’s pretty impressive inside too. The cabin is truly luxurious, the dashboard is well-stocked with instruments, and build quality is superb. There’s a sportingly low-slung driving position and ergonomics are first-rate, all the controls falling perfectly to hand. If you’re in the mood to relax, the ‘6’ can play the comfortable and refined grand tourer and it’ll cover miles with ease. But a prod of the organ-type throttle pedal will unleash impressive performance. The M635 is a bona fide supercar, too, though care is needed in the wet as tail-slides are never far away.
Power (bhp@rpm) 286bhp@6500rpm
Torque (lb ft@rpm) 251lb ft @4500
Top speed 156mph
WHAT TO LOOK FOR
BODYWORK & CHASSIS
Rust is a big enemy of the 6-Series, and signs of corrosion in the usual spots – rear arches, sills, and door bottoms – are likely to be the tip of the iceberg. The same applies to the front wings, which need particular scrutiny around the indicators and the lower rear section ahead of the sill, while inner wing seams can rot around the battery tray. With the wings alone costing £600 each, replacing both is a costly exercise and removal may be the only way of gauging the full extent of any problem.
Leaky rear light seals allow rust to develop in the boot, while water collecting around the rear spoiler and then dripping inside isn’t uncommon. Blocked drain holes can lead to corrosion around the sunroof opening and it pays to check for rot around the fuel tank and filler neck too. Get a good look underneath as corroded jacking points are a known issue – if these and the sills are bad, they can take the floor with them.
All models (bar the M635CSi) got a single cam ‘M30’ engine in various capacities. They’ll cover big miles before major attention is required but need looking after. Camshaft and rocker wear is caused by a clogged oil spray bar in the head, starving the cams of oil; ticking from cold is the giveaway. A perfect cooling system is vital, as overheating will quickly warp the alloy head, so check for a blocked radiator and ragged hoses and ensure the viscous-coupled fan kicks-in promptly.
The M635 engine (dubbed ‘M88’) was was a wet-sump derivative of the straight-six used in the M1 supercar and was a DOHC unit with 24 valves. A rebuild isn’t cheap, so fastidious maintenance is the key, with a history that includes cam chain replacement. BMW fitted a single row chain rather than the duplex arrangement on other models and it’s prone to breakage. It must be changed at 100,000 miles without fail.
Gearboxes were fouror five-speed manual or three- or four-speed auto, depending on age and model. All are generally tough, but make sure you try the later four-speed auto in all of its selectable drive modes. The manual-only M635 got a dog-leg Getrag unit which is hugely expensive to replace, so be wary of obstructive or crunchy gearshifts.
It’s a heavy car, so check the brakes and suspension for wear and tear. Early high-pressure braking system cars used ATF rather than brake fluid, shared with the power steering. Annual fluid changes are recommended while a hard pedal or lack of response points to the accumulator (or ‘brake bomb’ as it was known) failing. Later cars reverted to normal brake fluid. The steering box mount can crack where it attaches to the chassis crossmember, so ask the vendor about any remedial work, and watch for corrosion at the rear subframe mounts. The Michelin ‘TRX’ tyres fitted to most models are an unusual metric size and therefore tricky to find and costly to buy. Aftermarket Alpina replacements are popular. The correct type point to a careful owner. Cracked exhaust manifolds, leaks from fuel injector pipes and rough running caused by engine management issues need watching for.
Plenty of equipment and high-quality materials featured in the 6-Series, so check condition carefully. The genuine leather trim is expensive and you’ll need to ensure all the electrical toys are functioning properly. Electric seat motors can give up the ghost, while slow electric windows are often caused by hard grease from lack of use.
The 6-Series is a car that delivers looks and quality in spades, and that makes it seriously appealing in our eyes.Rot is a real concern though and it won’t necessarily be cheap to run, so you’ll want to find one that’s been pampered. But with this much style and performance on offer, it’ll be worth the effort.