Also, note that numerous frustrating electrical faults could be caused by a ‘weak’ battery, loose battery terminals or a bad alternator. Without proper voltage, the 6 Series’s countless electrical systems can malfunction. Your best bet against these problems is hooking the battery up to a ‘battery tender’ or similar device when you aren’t driving the 6 Series, especially for extended periods. As this is a car somewhat often used for short, occasional trips, maintaining a full battery charge can be difficult.

BMW 6 Series, 2004-2010
BMW 6 Series, 2004-2010. Click image to enlarge

Be wary of any model with features that aren’t working, or any model with warning or ‘check engine’ lights illuminated in the instrument cluster. Be sure to have any non-working systems or warning messages checked out by a BMW mechanic ahead of your purchase. Don’t take the sellers word for it that it’s not a serious problem – as they could be trying to pass an expensive repair bill off to you in the sale.

Avoid a model with the Active Steering system, which some online discussions suggest is overcomplicated, questionably reliable and not tremendously beneficial to the 6 Series’ driving experience. A malfunction with the Active Steering system could trip a warning light or cause the steering wheel to sit slightly sideways when travelling straight down the road.

Listen to the engine idling with the hood open. A rattling sound, possibly accompanied by a check-engine light, could be caused by a leak in an oil line that drives the variable valve timing system.

Look for signs of oil leakage from the valve covers on the 4.8L engine as well. Numerous owners have reported oil leaks from the valve covers, which would result in a puddle of oil beneath the vehicle. Look for this telltale sign, noting that oil may also leak from other seals in the engine, too. Here’s a link with some information on possible oil leaks.

BMW 6 Series, 2004-2010BMW 6 Series, 2004-2010BMW 6 Series, 2004-2010BMW 6 Series, 2004-2010
BMW 6 Series, 2004-2010. Click image to enlarge

A few other notes: First, avoid any model with extensive modification. Typically, performance modifications like intake and exhaust systems are safe, so long as the quality of the installation and parts are sound. Models with altered engine management software, nitrous, forced-induction or suspension changes (i.e. lowering, camber) should be avoided by shoppers that aren’t very familiar with the vehicle. These can add to driving enjoyment, but they can also cause tremendous headaches down the road.

Be sure to have the 6 Series’ tires, brakes and suspension checked over ahead of your purchase. If these parts are worn out or show excessive signs of abuse, it could be a sign that the unit you’re considering has had a hard life. Finally, budget for a full fluid change and tune-up if you’re unfamiliar with the service history of the model you decide on.

The Verdict: Shop patiently, looking for a low-mileage model, as much as your budget allows. Remember, too, that the looks, performance and overall driving experience are the big draws to the 6 Series as a used car buy, and that low running costs and gas mileage are not.

Skip 6 Series models with excessive, complicated options where possible. Opting for extended warranty protection and a pre-purchase mechanical inspection for your investment at a BMW garage are strongly advised.

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