A knock is the one noise you shouldn't wait out. The most likely causes ranked by how often we actually see them, what each costs, and how to tell the urgent ones from the ones that can wait.
A knocking noise that appears on cold start and fades as the engine warms is the classic early sign of bottom-end bearing wear - and on a Land Rover diesel, it should be diagnosed within days, not weeks.
Work through the ranked causes below, or use our diagnostic wizard to narrow it down by answering a few questions.
Owners describe engine knock in a handful of consistent ways. Which one matches yours narrows the field considerably.
Ordered by how frequently each appears across our Land Rover enquiry data - not alphabetically, and not cheapest-first.
| Cause | Likelihood | Affected Engines | Typical Cost | Severity |
|---|---|---|---|---|
| Crankshaft bearing wear | Very High | 306DT, 276DT | £6,500–£9,500 | Catastrophic |
| Timing chain tensioner wear | High | 204DTD, 204PT | £3,500–£5,800 | Immediate |
| V8 chain tensioner rattle | Medium | AJ133 | £2,800–£4,500 | Monitor |
| Injector or valvetrain noise | Medium | Most diesels | £450–£2,000 | Low |
This isn't a generic list assembled from forum consensus. The ranking reflects the actual proportion of "engine knocking" enquiries in our 2025 dataset that resolved to each of these four causes once properly diagnosed. Crankshaft bearing wear sits at the top not because it's inherently more common across every Land Rover engine, but because the 306DT and 276DT - the two engines most associated with it - are also two of the most numerous diesels in the parc reaching typical failure mileage right now. That's an important distinction covered fully on our data methodology page: a high rank reflects volume and vulnerability together, not a claim that bearing failure is somehow "normal." Timing chain tensioner wear ranks second largely because the pre-2019 Ingenium diesel is now the single most-enquired engine on this entire site, and its own weak point happens to present as a very similar noise.
Safe checks only. None of these require the vehicle to be raised or panels removed - if a check needs a lift, we've said so rather than telling you to attempt it.
Note whether it's only on cold start, only when warm, or constant. Cold-start-only that fades points strongly toward bearing wear.
From the driver's seat, with the vehicle stationary and in park. A knock rising directly with engine speed is bottom-end; one that stays constant is likely ancillary.
Low or contaminated oil accelerates every cause on this page. See the correct spec on our 306DT oil capacity guide.
Anything beyond this needs a specialist. Locating a knock properly requires a stethoscope on specific points of the block and, in most cases, the vehicle on a lift - not something to attempt on a driveway.
Knock accompanied by an oil pressure warning light, or a sudden loud knock with power loss. Continuing risks turning a repairable fault into a scrap engine.
Cold-start knock that's been getting gradually longer or louder over weeks. This is the window where the repair-vs-replace decision is still genuinely open.
A light tap that hasn't changed in months, no warning lights, no power loss, oil level correct. Still worth diagnosing, but not an emergency.
The spread here is wide because the causes are genuinely different jobs. Injector noise on a Discovery TD5 is a few hundred pounds; crankshaft bearing failure on a Range Rover Sport SDV6 is a full engine replacement. Whether that replacement is worth doing depends entirely on your vehicle's value - our repair vs replace framework shows the working, and the calculator runs your own numbers. Across our 2025 data the 306DT alone accounted for 980 UK enquiries [EM-VERIFIED] - full ranking on the Engine Failure Index 2026, and the per-engine breakdown on our 306DT failure rate page.
Two routes, depending on how certain you already are.
Run our diagnostic wizard - it narrows the four causes above by asking about timing, load and warning lights.
Use the registration lookup to confirm your exact engine code before pricing anything.
Read the specific failure page, then check whether replacement makes sense on your vehicle. Real owner outcomes are in our Discovery SDV6 case study.
Briefly and gently, if there is no oil pressure warning and no power loss - but you should be driving it to a specialist, not continuing normal use. If the knock is accompanied by an oil pressure light, stop immediately; continuing at that point is what turns a repairable engine into a scrap one.
Cold-start knock that fades as the engine warms is the classic signature of bearing wear. Cold oil is thicker and takes a moment to reach the bearings; once warm, oil pressure masks the noise. It fading does not mean it is improving - it usually means it is early.
Most independent JLR specialists charge for an hour or two of diagnostic time, typically £90–£220 depending on region. Many will offset this against the job if you proceed with them.
No. Timing chain tensioner wear, V8 chain rattle and injector noise all produce knocking or tapping sounds and cost substantially less to resolve than a crankshaft bearing issue.
If the knock is caused by genuinely low oil level, topping up can reduce the noise temporarily, but it does not undo any bearing wear that has already occurred and the underlying cause still needs diagnosing.
Causes Ranked By Real DataOrdered by actual enquiry frequency, not guesswork.
Safe Checks OnlyWe never tell you to get under a car - see our editorial standards.
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