BMW 340i common problems and MOT failures
What goes wrong on a used BMW 340i, year by year: known faults from UK buying guides, the parts flagged at MOT more than on other cars (from 2,715 MOTs done during 2023–2025), and what to check before you buy one.
Pick the year
Most years have their own guide. The year is when the car was first registered (it’s on the logbook, or check the reg below).
What usually goes wrong with a BMW 340i?
Known faults reported by owners, mechanics and UK buying guides, in our own words. Most apply to certain years or engines only, so check which the car has.
- Cars registered 2016–2019 · 2.0 petrol and diesel
Timing chain wear
The four-cylinder petrol and diesel engines can suffer timing chain wear, especially with late oil changes. A failed chain is an engine-out repair.
At the viewing: Listen for a rattle or whine from the back of the engine, especially from cold. Ask for oil changes on time.
- Cars registered 2016–2019 · Diesel
Blocked EGR valve or particulate filter (diesel)
Diesels used mostly for short trips can block the EGR valve or clog the particulate filter, causing poor running.
At the viewing: Ask what journeys it’s done and watch for warning lights or a lack of power.
If it needs doing: DPF clean or regeneration, about £160–£500. ClickMechanic
- Cars registered 2016–2019
Noisy differential
A whine from the rear as the car passes you can mean the differential has been neglected.
At the viewing: Ask someone to drive it past you slowly and listen for a whine from the back.
BMW 340i MOT pass rate by year
Of the years since 2005 with plenty of MOT tests, the 2017 BMW 340i did best (90% passed first time, 10 points above all 2017 cars) and the 2018 did worst (92%, 9 points above all 2018 cars). Older cars fail more, so compare each year with all cars registered the same year.
Questions to ask the seller before buying a BMW 340i
Ask before you travel to see it. A seller who knows the car will have answers, and receipts.
- Has the timing chain been checked or replaced, and have oil changes been on time?
- Can I see the service history and receipts for any big jobs?
Looking at a BMW 340i?
Check the actual car: its own MOT history and what to ask the seller. Free, no sign-up.
Where this comes from: MOT figures are the DVSA’s anonymised results for every MOT test done in Great Britain during 2023–2025, grouped by the year each car was first registered. How many are on the road is from the Department for Transport’s vehicle licensing statistics. Known faults are from UK buying guides, in our own words, with links. How we score