What are the most common problems with a 2018 BMW 6 Series diesel?

The biggest MOT weak spot is flexible couplings: flagged on 4.1% of tests, null× the rate for all 2018 cars, followed by drive shaft (cv) joints (2.5%).

What should I ask the seller before buying a used 2018 BMW 6 Series diesel?

Any recent work on the flexible couplings? (Flagged at MOT null× as often on the 2018 BMW 6 Series diesel as on other cars the same age.) Any recent work on the drive shaft (cv) joints? (Flagged at MOT 3.1× as often on the 2018 BMW 6 Series diesel as on other cars the same age.) Any recent work on the engine warning light? (Flagged at MOT 2.3× as often on the 2018 BMW 6 Series diesel as on other cars the same age.) Can I see the service history and receipts for any big jobs?

Used car guide

2018 BMW 6 Series diesel: common problems and MOT failures

What MOT testers find on the diesel BMW 6 Series first registered in 2018 (diesel cars only): we looked at the 3,243 MOTs these cars had during 2023–2025. Plus known faults and what to look at before you buy one.

3,243MOTs of 2018 diesel cars, done in 2023–2025

88%pass first time (all 2018 cars: 83%)

9,400typical miles a year

null×the usual rate for flexible couplings

What goes wrong more than usual on a 2018 BMW 6 Series diesel?

Parts flagged at MOT more often on the 2018 BMW 6 Series diesel than on all cars registered in 2018.

Flexible couplingsnull× usual

BMW 6 Series
4.1% All 2018 cars
0%

Failed outright at MOT: 0.3%, against 0% of all 2018 cars. The rest were advisories or minor defects.

Rough price £150–£1,000 our estimate

At the viewing: Check the sills, wheel arches and underneath for rust, and look along the panels for uneven gaps or paint.
Drive shaft (CV) joints3.1× usual

BMW 6 Series
2.5% All 2018 cars
0.8%

Failed outright at MOT: 1.2%, against 0.4% of all 2018 cars. The rest were advisories or minor defects.

Rough price £60–£350 our estimate

At the viewing: Drive slowly on full steering lock in both directions and listen for clicking. Look for split rubber boots behind the front wheels.
Engine warning light2.3× usual

BMW 6 Series
2.1% All 2018 cars
0.9%

Failed outright at MOT: 2.1%, against 0.9% of all 2018 cars. The rest were advisories or minor defects.

Rough price £10–£80 our estimate

At the viewing: Ask a friend to check every light while you work the switches: indicators, brake lights, fog lights and reversing lights.

Better than most

Brake discs: 3.2% here, against 9.8% of all 2018 cars.

Common 2018 BMW 6 Series diesel MOT failures and advisories

The share of 2018 BMW 6 Series diesel MOT tests where testers flagged each area, as a fail or an advisory. Rough prices are typical independent-garage costs.

Tyres

21% of testsRough price £70–£150

At the viewing: Check the tread on all four tyres, including the inside edges, and look for cracks or bulges.
Brakes

10% of testsRough price £150–£350

At the viewing: Look for a lip on the disc edges and feel for judder or pulling when braking firmly from about 40mph.
Lights and electrics

7% of testsRough price £10–£80

At the viewing: Ask a friend to check every light, including brake lights and indicators, while you operate them.
Wipers, windscreen and mirrors

4% of testsRough price £15–£250

At the viewing: Check for chips in the driver's view, and test the wipers and washers.
Driveshafts and joints

3% of testsRough price £60–£350

At the viewing: On full steering lock, drive slowly and listen for clicking from the front wheels.
Suspension

2% of testsRough price £120–£400

At the viewing: Listen for knocks over speed bumps, and look behind each front wheel for a snapped coil spring.

Questions to ask the seller before buying a 2018 BMW 6 Series diesel

Ask before you travel to see it. A seller who knows the car will have answers, and receipts.

Any recent work on the flexible couplings? (Flagged at MOT null× as often on the 2018 BMW 6 Series diesel as on other cars the same age.)
Any recent work on the drive shaft (cv) joints? (Flagged at MOT 3.1× as often on the 2018 BMW 6 Series diesel as on other cars the same age.)
Any recent work on the engine warning light? (Flagged at MOT 2.3× as often on the 2018 BMW 6 Series diesel as on other cars the same age.)
Can I see the service history and receipts for any big jobs?

Looking at a BMW 6 Series?

Check the actual car: its own MOT history, mileage and what to ask the seller. Free, no sign-up.

Other years

Every year of the BMW 6 Series compared

Year	MOT tests	Most flagged
2026	–	Too new for MOT data
2020	730	Tyres 23%
2019	3,162	Tyres 23%
2017	767	Tyres 25%
2016	–	Too few tests
2015	–	Too few tests
2014	–	Too few tests
2013	2,110	Tyres 26%
2012	1,554	Tyres 24%
2011	229	Tyres 20%
2010	–	Too few tests
2009	149	Tyres 30%
2008	248	Suspension 34%
2007	254	Suspension 33%
2006	427	Brakes 33%
2005	212	Brakes 33%
2004	–	Too few tests
2003	–	Too few tests
1990	–	Too few tests
1989	–	Too few tests
1988	–	Too few tests
1987	–	Too few tests
1986	–	Too few tests
1985	–	Too few tests
1984	–	Too few tests
1983	–	Too few tests
1982	–	Too few tests
1981	–	Too few tests
1980	–	Too few tests
1979	–	Too few tests
1978	–	Too few tests
1977	–	Too few tests

Where this comes from: the DVSA's anonymised results for every MOT test done in Great Britain during 2023–2025, counting the MOTs of BMW 6 Series cars first registered in 2018. "Flagged" includes advisories, so it isn't the same as a fail rate. How we score