(2015 320d cohort)
presentation
at test
defect group
The 2015 BMW 320d is one of the most common used diesel saloons in the UK, and after a decade on the road its failure pattern is very well documented. The MOT test records every defect found by category, which means we can rank what actually goes wrong — and separate the items that fail a car from the advisories that simply warn you what’s coming next.
Figures are derived from the DVSA anonymised MOT tests and results dataset, published under the Open Government Licence v3.0. Every MOT records the test outcome plus each defect as a coded “reason for rejection” or advisory. We filter to BMW 320d vehicles first registered in 2015 and report the most recent full test year.
Percentages are share of tests, not share of failures — so “2.6% tyre tread” means 2.6 in every 100 tests failed for that item. A single test can record several defects, so the columns do not sum to 100%.
Top 10 MOT failure items
These are the defects that actually caused a 2015 320d to fail its MOT, ranked by how often they appear. Note how heavily the list leans towards suspension, tyres and brakes — wear items, not engine failures.
Most common MOT advisories
Advisories are the early-warning layer. They don’t fail the car, but they tell you what the next owner will be paying for. On a 2015 320d, advisories are far more common than failures — and they are the single most useful thing to read before you buy.
| Advisory item | Share of tests | What it means |
|---|---|---|
| Brake pads wearing thin | 14.2% | Budget £180–£320 per axle within a year. |
| Tyre worn close to legal limit | 12.8% | Staggered rear tyres on M Sport cost more. |
| Suspension bush deteriorated / slight play | 11.6% | Front control arm bushes are the usual culprit. |
| Corrosion to brake pipes / underbody | 9.4% | Watch this one — it escalates to a failure. |
| Shock absorber light misting or seepage | 6.7% | Precursor to the No.3 failure item above. |
| Engine or gearbox oil leak (not excessive) | 6.1% | Often the sump gasket or oil filter housing. |
| Brake disc lipped or scored | 5.8% | Usually replaced together with pads. |
| Exhaust minor leak or corrosion | 3.9% | Check it isn’t the DPF section. |
| Ball joint dust cover deteriorated | 3.4% | Cheap now, joint replacement later. |
| Anti-roll bar link slight play | 3.1% | Common knocking noise over bumps. |
Which system fails most
Grouping every recorded defect by vehicle system shows where the money goes on a ten-year-old 320d.
Across 689,310 MOT tests on all BMW 3 Series variants, the pass rate is 79.2% — slightly above the UK average for its class. Diesel 3 Series models pass at 79.8%, marginally ahead of petrol at 77.9%. Median mileage at test is 122,448 miles and 48% of failures are safety-related.
A 2015 car sits above that average simply because it is younger than much of the fleet: 2014-registered 3 Series pass at 82.8%, rising to 89.3% for 2017 cars.
Model averages describe the model. Enter the registration to see this car’s real MOT history, every recorded advisory, its mileage timeline and any finance, theft or write-off markers.
N47 vs B47: the 2015 split that matters
This is the single most important thing to establish about a 2015 320d, and it is the reason model-year averages can mislead you. 2015 is the changeover year. The F30 320d switched from the older N47 engine to the redesigned B47 around the mid-2015 facelift (LCI). Two cars on the same 2015 plate can have completely different risk profiles.
- Timing chain stretch is the headline risk. The chain sits at the gearbox end of the engine, so replacement means removing the gearbox.
- Failures typically reported between 80,000–120,000 miles, occasionally earlier.
- Indicative repair £2,500–£3,500 at an independent specialist; more at a main dealer.
- Swirl flap and inlet manifold carbon build-up also more common.
- Revised chain drive. BMW addressed the N47’s core weakness; reported failures are far rarer.
- Euro 6 emissions with NOx sensors — a new failure point (see below).
- Slightly more power and better refinement; same 8-speed ZF transmission.
- Still a diesel — DPF and EGR care applies equally.
Known faults the MOT won’t catch
The MOT tests roadworthiness, not mechanical health. A 320d can pass cleanly with a failing turbo or a blocked DPF. These are the expensive items owners actually report — costs are indicative UK independent-specialist ranges, not quotes.
Pre-purchase checklist
Work through this in order. The first three cost nothing and rule out most bad cars.
- Confirm the engine. N47 or B47? Check the V5C and build date, not the plate.
- Read the full MOT history. Look for repeated advisories, corrosion warnings that escalate, and any mileage that goes backwards.
- Build a mileage timeline. Roughly 10,000–12,000 miles a year is normal for a diesel of this age. Flat or falling readings need explaining.
- Ask how it was driven. Motorway miles suit this car; short urban trips are what kill DPFs.
- Check outstanding recalls — particularly the EGR programme.
- Verify finance, theft and write-off markers before money changes hands.
- Listen on a cold start. A rattle from the gearbox end on an N47 is the sound you are listening for.
- Budget for wear items. On the advisory data above, assume pads, tyres or bushes are due within a year.
FAQs
Is a 2015 BMW 320d reliable?
Broadly yes, by the numbers. The 3 Series passes MOT at 79.2% against a lower class average, and the failure list is dominated by ordinary wear items rather than drivetrain faults. The caveat is the engine: a pre-facelift N47 car carries timing chain risk that a later B47 car largely does not.
What fails a 320d MOT most often?
Worn suspension arm bushes and joints, closely followed by tyre tread depth and leaking shock absorbers. Suspension accounts for roughly 31% of all recorded defects on this cohort.
Does the 2015 320d have the timing chain problem?
It depends entirely on build date. Cars built before the mid-2015 facelift use the N47 engine, which is the one associated with chain stretch. Facelift cars use the B47 with a revised chain drive. Always confirm the engine code rather than assuming from the registration year.
Is high mileage a problem on a 320d?
Less than you’d think. These engines are built for motorway work, and a 130,000-mile car with full service history and consistent MOT records is often a safer buy than a 60,000-mile car that only did short urban journeys — the latter is far more likely to have DPF and EGR trouble.
How much should I budget for running costs?
The average MOT repair bill across 3 Series cars is around £113, but that is the mid-point of a wide range. Given the advisory data, a realistic annual maintenance budget for a ten-year-old 320d is several hundred pounds, plus a contingency for one larger item.
A CarCheckReport covers MOT and advisory history, mileage anomalies, outstanding finance, insurance write-off records, stolen markers, import and scrapped status — using DVLA, DVSA and Experian data.