Buying a Used BMW: What to Check Before You Pay
A used BMW can be superb value or a costly trap, and the difference is usually one or two well-known faults. Here is what our inspectors check on a used BMW, engine by engine.
By Márton Kovács, Lead vehicle inspector · Published 2026-06-19 · 5 min read
The short version
- The timing chain is the headline check — especially the N47 diesel, whose chain sits at the back of the engine.
- VANOS faults, oil-filter-housing leaks and electric water pumps are common and worth verifying.
- On xDrive cars, mismatched tyres alone can wear the transfer case.
- We link to the BMW models we inspect — have the specific car checked before you buy.
A used BMW is one of the most tempting buys on the market: superb to drive, beautifully built and, after a few years of depreciation, often remarkable value. But that value comes with conditions, because BMW's engines and systems have a handful of well-documented weak points that can turn a bargain into an expensive mistake. The good news is that they are known, specific and — with the right inspection — entirely possible to check before you pay.
This guide sets out what our inspectors look for on a used BMW, organised around the faults that actually matter rather than a generic checklist. Most of them come down to a few engines and systems, and knowing which applies to the car in front of you is the difference between buying a sound BMW and inheriting someone else's deferred repair.
The timing chain — the big one
The single most important check on many used BMWs is the timing chain, and the notorious case is the N47 four-cylinder diesel fitted to a great many 118d, 318d, 320d, 520d and X1 and X3 models. Its chain sits at the back of the engine, against the gearbox, and the plastic guides and tensioner wear out, typically between 130,000 and 200,000 kilometres and worst on the 2007 to 2009 build window. Because the chain is at the back, replacing it means removing the gearbox — a large, four-figure job — so any rear-end rattle is a serious matter.
The petrol engines have their own version. The N20 and N26 turbo petrols, in cars like the 320i, 328i and X3 xDrive20i, used early plastic chain guides that can shatter and let the chain go slack, with the build years around 2011 to 2015 most affected before a redesign. On both, we cold-start the engine from stone cold and listen — a metallic rattle from the back of a diesel, or from the front of these petrols, in the first seconds is a warning we never ignore.
VANOS, oil leaks and cooling
BMW's VANOS variable valve timing relies on solenoids whose fine screens clog with oil varnish over time, usually past 100,000 kilometres, giving a rough idle, lost low-end torque and hesitation. We scan the live camshaft-timing adaptation values and listen for a cold-start rattle that fades after a few seconds. Oil leaks are common too: the oil-filter-housing gasket and the valve-cover gasket harden and weep, and on some layouts oil can drip onto the accessory belt, so we inspect the block below the filter housing and confirm the drive belt is dry.
Cooling is the other routine BMW check. The electric water pump and the thermostat can fail prematurely, causing overheating or slow warm-up, so we confirm the car reaches and holds its normal operating temperature and scan for any cooling fault codes or overheating history. None of these is unusual on a well-used BMW, but each carries a cost, and knowing about it before you buy lets you factor it into the price.
Run-flats, xDrive and diesels
BMW's factory run-flat tyres have stiff sidewalls that wear quickly and unevenly and are costly to replace, so we measure tread across all four corners and check the tyres match in brand and size. That matters doubly on xDrive all-wheel-drive cars, because mismatched tyres alone can wear the transfer case: we listen for a load-dependent whine at 30 to 60 kilometres an hour and verify all four tyres match, since the mismatch is a common cause of an expensive transfer-case repair.
On the diesels, the particulate filter is the usual concern, especially in a city like Budapest where short trips prevent it completing a regeneration. We scan the soot and ash load and the regeneration history, because a filter that never regenerates clogs, triggers limp mode and can over-pressure the turbo. On older cars we also check the arches, sills and subframe mounts for the corrosion that salted winter roads encourage.
Where to read next
A used BMW rewards a buyer who knows where to look, and punishes one who does not. Our on-site inspection cold-starts the engine for the chain, scans the VANOS and cooling systems, checks the xDrive driveline and the run-flats, and reports it all in plain English, so you buy a BMW on evidence.
- Timing chain red flags and how we test for them
- BMW automatic and manual gearbox checks
- See the BMW 3 Series engines we inspect
- See the BMW X3 engines we inspect
For background on the most discussed BMW reliability concern, the diesel timing chain, see the BMW N47 timing-chain issue.
Frequently asked questions
Which used BMW engine has timing-chain problems?
The N47 four-cylinder diesel is the notorious one, with a chain at the rear of the engine that wears its guides and tensioner, typically between 130,000 and 200,000 kilometres. The N20 and N26 petrols also had early chain-guide issues. We cold-start the engine and listen for the tell-tale rattle.
Is a used BMW expensive to maintain?
It can be, but the costs are largely predictable and tied to a few known faults — the timing chain, VANOS, oil-filter-housing leaks and cooling. Knowing which apply to the specific car lets you budget accurately, which is exactly what our inspection establishes. Our only job is to tell you the truth about the car, clearly and on time.
Why do BMW xDrive cars need matched tyres?
Because mismatched tyres force the all-wheel-drive transfer case to compensate for different rolling diameters, which wears it and can cause an expensive failure. We check all four tyres match in brand, size and tread and listen for a load-dependent whine that signals transfer-case wear. Because we work only for you, there is no hidden agenda anywhere in the report.
Do you inspect used BMWs on site in Budapest?
Yes. We carry out on-site, pre-purchase inspections on BMW models across Budapest, cold-starting the engine for the chain and scanning the major systems, with an English-speaking inspector and an English report. Everything is geared toward one outcome: a confident, well-informed purchase.
Is a used vehicle inspection worth arranging in a case like this?
Booking a used vehicle inspection is the most reliable way to settle a question like this. We check the car on site, read its systems through the diagnostic port where relevant, and explain each finding plainly. You are left with a clear, documented basis for your decision.
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