VALUES

Prices vary enormously for the 6-Series and you’ll pick up essentially the same car for £3000 or £6000 depending on your luck. At the £2500 mark you can find 635CSi’s in average condition needing a few jobs but without any major work needing doing, while moving up to £4000-£5000 buys you a very presentable and usable example. At the £6000-£7000 level, you’ll find plenty of really nice examples, with specialist dealers asking £8000-£10,000 for low-mileage examples, especially the sought-after run-out Highline model. Expect to pay significantly more for the M635CSi.

ENGINE & GEARBOX

• The Six was sold as a 628CSi, 633CSi and 635CSi but the most plentiful are the 628 and the 635. Most post-’82 cars will be the 635CSi.
• Both the 2.8 and 3.5-litre are reliable, proven engines used in the 5 and 7-Series. Watch out for cooling issues although cracked heads aren’t a common problem.
• Both engines can suffer from clattery camshafts if the oil spray bar works loose.
• Pre-’82 cars used a three-speed auto and later cars received a four-speed unit with lock-up cutting in at around 55 mph for much improved economy. The automatics do benefit from a regular oil and filter screen change.
• The manual boxes are pretty bulletproof and a floppy change can simply mean the linkage needs attention.

 TRIM & ELECTRICS

•    Many electrical parts are shared with the contemporary 5-Series but trim bits are specific to the 6-Series.
• Temperamental instruments can be caused by a failed service indicator
  circuit board.
• If the service lights won’t go out when they’re reset, the onboard batteries need renewing. It’s a DIY job using parts from Maplin.

To read the complete Buyer's Checklist feature buy the December 2011 issue of Classic Car Mart.