1
X100 (1996–2006)
--
1996–2006 • 4.0 AJ27 V8
★★★★★
JaguarXK1996–20142 Generations
AJ-V8XK Engines - The Complete UK Guide
Two generations of Jaguar's V8-powered grand tourer - X100 and X150 - covered from the 4.0 AJ27 to the 5.0 AJ133 supercharged. Real UK failure patterns, honest replacement economics, and costs you can actually trust. Backed by 290+ real UK XK engine enquiries in 2025 [JAG-VERIFIED].
Explore XK Engines
290+Enquiries (2025) [JAG-VERIFIED]
2Generations Covered
6Engine Codes
Part of Engine Finders
XK -
The Ownership Verdict
Verdict MetricOur Call
Overall Ownership Rating★★★★☆
Replacement Economics⚠️ The XK rule: generation and engine choice determine whether replacement makes financial sense - an early 4.0 XK8 can fail the threshold, a 5.0 XKR-S comfortably passes it
Reliability★★★★☆
Most Reliable EngineAJ133 5.0 V8 - revised timing chain tensioner design from 2009 onward, robust supercharged V8
Highest-Risk EngineAJ27 4.0 V8 - bore wear and timing chain tensioner issues on early X100 cars [PATTERN DATA]
Best Used BuyX150 (2009–2014) 5.0 naturally aspirated - facelift car, revised engine, strong value retention
Average Engine Replacement£3,000–£9,000 supply-only [JAG-QUOTE]
Most Common Failure EnquiryAJ133 5.0 V8 timing chain tensioner [JAG-VERIFIED]
Jaguar Ranking💎 Premium Style - the grand tourer that defines Jaguar elegance
XK
at a Glance
MetricValue
Generations2 (X100 1996–2006, X150 2006–2014)Years Produced1996–2014Engine Codes Tracked6
Fuel TypesPetrolMost Enquired Engine (2025)AJ133 / 508PN (5.0 V8) - 330 enquiriesJAG-VERIFIEDMost ReliableAJ133 5.0 V8 (post-2009)Highest-RiskAJ27 4.0 V8 (pre-2000 bore wear)Typical Replacement Cost£3,000–£9,000 supply-onlyJAG-QUOTETypical Host Value£4,000–£35,000THIRD-PARTYOverall Rating★★★★☆Generations
2 (X100 1996–2006, X150 2006–2014)
Years Produced
1996–2014
Engine Codes Tracked
6
Fuel Types
Petrol
Most Enquired Engine (2025)
AJ133 / 508PN (5.0 V8) - 330 enquiries
JAG-VERIFIEDMost Reliable
AJ133 5.0 V8 (post-2009)
Highest-Risk
AJ27 4.0 V8 (pre-2000 bore wear)
Typical Replacement Cost
£3,000–£9,000 supply-only
JAG-QUOTETypical Host Value
£4,000–£35,000
THIRD-PARTY
Overall Rating
★★★★☆
A perfect blend of performance, engineering excellence, and drivability.
XK Generations -
Find Your Vehicle
Two generations of V8-powered grand touring - the steel-bodied X100 and the aluminium-monocoque X150.
2
X150
(2006–2014)(2006–2014)
2006–2014 • 4.2 AJ34 V8
★★★★★
3
The 2009 Facelift - The Dividing
LineLine
Pre-2009 (4.2-litre): The original X150 launched in 2006 with the 4.2 AJ34 V8 - a proven unit, but the 5.0 that replaced it is objectively better in every way.
★★★★★
Read the full comparison: X100 vs X150
XK Engine Codes -
The Complete Database
Every V8 that powered the XK - verified factory codes, real UK enquiry data, and honest reliability ratings.
| Engine Code | Family | Fuel | Disp. | Power | Years | Gen. | Reliability | 2025 Enquiries | Avg. Recon Cost |
|---|---|---|---|---|---|---|---|---|---|
| AJ27 | AJ-V8 | Petrol | 4.0L | 284–290 bhp | 1996–2002 | X100 | ★★★★★ | [PATTERN DATA] | £3,000–£5,000 |
| AJ27S | AJ-V8 Supercharged | Petrol | 4.0L | 370 bhp | 1998–2002 | X100 | ★★★★★ | [PATTERN DATA] | £3,500–£5,500 |
| AJ34 | AJ-V8 Gen II | Petrol | 4.2L | 300–305 bhp | 2002–2009 | X100 (2002–06) / X150 (2006–09) | ★★★★★ | [PATTERN DATA] | £3,500–£6,000 |
| AJ34S | AJ-V8 Gen II Supercharged | Petrol | 4.2L | 390–420 bhp | 2002–2009 | X100 (2002–06) / X150 (2006–09) | ★★★★★ | [PATTERN DATA] | £4,500–£7,000 |
| AJ133 | AJ-V8 Gen III | Petrol | 5.0L | 385 bhp | 2009–2014 | X150 | ★★★★★ | 330 [JAG-VERIFIED] | £5,500–£9,000 |
| AJ133S | AJ-V8 Gen III Supercharged | Petrol | 5.0L | 503–542 bhp | 2009–2014 | X150 | ★★★★★ | [JAG-VERIFIED] | £6,500–£10,000 |
Showing 6 of 6 engine codes
★★★★★ Poor★★★★★ Average★★★★★ Good★★★★★ Excellent
All enquiries are from 2025 (to date) and verified via our internal system. Recon costs are supply only and exclude fitting.
Proprietary UK Data
Every figure below is powered by real UK owner enquiries in 2025. This is data you won't find anywhere else.
Engine CodeFuel2025 EnquiriesView
AJ133Petrol330
Petrol330AJ133SPetrol-
Petrol-AJ27Petrol-
Petrol-AJ27SPetrol-
Petrol-AJ34Petrol-
Petrol-AJ34SPetrol-
Petrol-No engine codes match these filters.
Data sources:
Enquiry volumes:
Proprietary UK enquiry data 2025 [JAG-VERIFIED]
Costs:
Engine Replacement Economics [JAG-QUOTE]
Engine codes:
Cross-referenced from verified factory data
Common XK
Engine Problems
What actually fails on the XK's AJ-V8 engines - and what it costs to fix.
01AJ27 4.0 V8 Bore Wear
Monitor
Monitor
Early X100 engines (pre-2000) can suffer cylinder bore wear, causing misfires and blue exhaust smoke on throttle. Full engine rebuild is the only permanent fix.
Read more02AJ-V8 Timing Chain Tensioner Wear
Monitor
Monitor
Pre-2009 AJ27 and early AJ34 engines have a documented timing chain tensioner weakness. Cold-start rattle is the early warning sign - catastrophic if ignored.
Read more03AJ133 5.0 V8 Water Pump Failure
Immediate
Immediate
The 5.0 V8's water pump is a known weak point across the AJ133 family. Owner reports confirm it's a routine replacement item - catch it before overheating causes head-gasket damage.
Read more04ZF 6-Speed Gearbox Torque Converter
Monitor
Monitor
Shared across the X150 range - torque converter lock-up clutch failure causes gearbox slippage, grinding noises and transmission warning lights.
Read more05Battery Drain & Electrical Gremlins
Low
Low
XKs are sensitive to battery condition - modules failing to sleep correctly is a frequent no-start complaint. Always use a premium battery.
Read more06Fuel Injector Failure (5.0 V8)
Low
Low
Faulty injectors on the 5.0 AJ133 cause rough running, reduced power, stalling and excessive fuel consumption.
Read moreUrgency Key
Catastrophicstop driving, specialist inspection immediately
Immediatebook inspection now
Monitorbook inspection soon
Lowplan at next service
XK Market Intelligence - What 290+ UK Owners Told Us in 2025
290++
Total Enquiries in 2025
[JAG-VERIFIED]
Signal
2025 Data
Demand Trend
X100 Enquiries
120 [JAG-VERIFIED]
Stable
X150 Enquiries
Approx 170 [JAG-VERIFIED]
Rising
AJ133 / 508PN Enquiries (all models)
330 [JAG-VERIFIED]
Rising
Most Enquired Generation
X150 (2006–2014)
Rising
Insights from the data:
Interesting insight: The X150 generation accounts for roughly 60% of all XK enquiries in 2025 - the aluminium grand tourer is the one buyers are actively researching, while the X100 is increasingly the preserve of collectors and enthusiasts
The 5.0 AJ133 engine (fitted to 2009–2014 X150s) generates significantly more enquiry volume than any other XK engine - buyers are actively seeking the post-facelift car, and specialists report this is the generation with the strongest reliability record
Early 4.0 X100 cars generate relatively low enquiry volume but high forum activity - the enthusiast community is active, but the cars are now cheap enough that a full engine replacement often fails the economics threshold for all but the best examples
Editorial Pull-Quote
The One Thing We'd Tell Every XK Buyer
“Buy a 2009–2014 X150 with the 5.0 naturally aspirated V8, full service history, and evidence the water pump has been replaced. It's the sweet spot - the most reliable engine, the best-looking generation, and values that are still £10,000–£20,000 below where they should be.”
XK Engine Replacement
Costs - By Generation
Real UK pricing for every XK V8 - used, reconditioned and rebuilt, supply-only, with independent labour guidance.
TransparentReal UK PricesQuality AssuredTested Engines
Fitted by ExpertsTrusted Garages12 MonthsWarrantyTransparentReal UK PricesQuality AssuredTested EnginesFitted by ExpertsTrusted Garages12 MonthsWarrantyImportant Notes Fitting an XK engine typically takes 12–18 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer) [JAG-QUOTE].
Labour Estimate Fitting an XK engine typically takes 12–18 hours at £65–£95/hr (independent) or £110–£160/hr (London/SE dealer) [JAG-QUOTE].
The XK Engine Replacement Costs rule - generation is everything:
Value the car first; the engine decision follows.
All prices in GBP (£) • Supply only • Subject to availability and condition
How the XK Engine Range Evolved
1996 to 2014
Follow each era of this model's engines — what launched, what was revised, and what buyers need to know before committing.
4 Eras1996 to Present8 Key EnginesAcross the timelineHardware Revisions2009–2014Buyer FocusedWhat changed & whyEra
Years
Key Engines
Why Jaguar Changed
Worth Knowing
The AJ27 Era
1996–2002
AJ27 4.0 V8AJ27S 4.0 Supercharged
The original XK8 launched with Jaguar's new 4.0-litre V8 - a clean-sheet design replacing the straight-six XJS.
Early cars (pre-2000) have a reputation for bore wear - always inspect before buying.
The 4.2 Upgrade
2002–2006
AJ34 4.2 V8AJ34S 4.2 Supercharged
Jaguar increased displacement to 4.2 litres in 2002, bringing more power and improved reliability - the bore-wear issues were largely resolved.
The 4.2 is significantly more robust than the early 4.0 - this is the X100 to target.
The Aluminium Revolution
2006–2009
AJ34 4.2 V8AJ34S 4.2 Supercharged
The X150 launched with an aluminium monocoque, losing 150kg over the X100 - the 4.2 engine carried over initially.
The X150 chassis is a masterpiece - Ian Callum's finest work.
The 5.0 Transformation
2009–2014
AJ133 5.0 V8AJ133S 5.0 Supercharged
The 2009 facelift brought the 5.0-litre AJ133 V8 with 385bhp (naturally aspirated) and up to 542bhp (supercharged) - plus a revised timing chain tensioner design.
This is the definitive XK engine - more power, stronger reliability, and the one specialists recommend.
Key Engines AJ27 4.0 V8, AJ27S 4.0 Supercharged
Why It Changed The original XK8 launched with Jaguar's new 4.0-litre V8 - a clean-sheet design replacing the straight-six XJS.
Worth Knowing Early cars (pre-2000) have a reputation for bore wear - always inspect before buying.
Engine reliability insights and failure patterns are based on verified UK enquiry data. [JAG-VERIFIED]
Who Should Buy an XK?
Different buyers, different priorities. Here is our verdict on who the XK is perfect for - and who should think twice.
Built for Real LifePractical. Powerful. Proven.- Data-Backed RatingsUK enquiries analysed in 2025.
- Honest VerdictsNo hype. Just the truth about ownership.
- Buyer-FocusedFind the right model for your needs.
Buyer Profile
Rating
Our Verdict
Performance Buyer
★★★★★
★★★★★
The XKR-S is one of the most underrated performance cars on the used market - 542bhp, 200mph+, and values that haven't yet caught up to the driving experience. Buy a 2012+ car with full service history.
Daily Commuter
★★★★★
★★★★★
The XK is a genuine GT - comfortable, refined, and capable of daily use. But be realistic: fuel economy is 18–25mpg, and maintenance costs reflect the original £70,000 price tag. A 2009+ 5.0 naturally aspirated is the sweet spot.
Family Buyer
★★★★★
★★★★★
The XK is a 2+2 at best - rear seats are tiny, and even children will complain. This is a car for couples, not families. If you need practicality, look at the F-Pace instead.
Budget Owner
★★★★★
★★★★★
An early X100 can be bought for under £5,000 - but a £5,000 engine replacement will quickly exceed the car's value. Buy the best X150 5.0 you can afford, not the cheapest X100 you can find.
Collector / Keeper
★★★★★
★★★★★
The XK, especially the X150, is a future classic. Low-mileage examples with full service history are already appreciating. The XKR-S and Portfolio models are the ones to hold long-term.
Real talk. The right XK for you depends on your budget, your mileage, and your patience for maintenance. Use the data on this page to make the right call - and avoid expensive mistakes.
Diagnostic Calculator
Can I Repair My XK Engine - or Should I Replace It?
The XK presents one of the widest economics swings in the Jaguar range - a £5,000 reconditioned engine in a £4,000 X100 is a financial mistake, but the same engine in a £30,000 XKR-S is a no-brainer.
Run the numbers before you commit.
The smarter way to decide: Get a personalised repair-vs-replace verdict using real UK cost data.
Know your engine?
Launch the Jaguar diagnostic calculator with XK pre-selected.
Launch Jaguar Diagnostic CalculatorXK pre-selected
XK pre-selectedAll generations covered- Real UK cost dataUsed, recon & rebuilt
- Instant verdictRepair vs replace
Not sure which engine you have?
We'll identify it first.
Identify My Engine FirstThen launch the diagnostic calculatorIdentification is the first step inside the tool.
We'll pinpoint your exact engine code before running the diagnostics.
Stop guessing. Get the right answer.
Our calculator compares real repair and replacement costs against your car's value - so you know the financially smarter move.
Trust Signals
Why XK Owners Trust
jaguarengines.uk
Built on Real Data Every reliability rating and cost range in this XK guide comes from genuine UK quote and enquiry data - 290+ real XK enquiries in 2025 [JAG-VERIFIED] - not manufacturer marketing, not forum guesswork.
We Tell You When Not to Repair The XK rule is clear: if reconditioned engine cost exceeds roughly 60% of what your specific car is worth, get a scrap valuation alongside any repair quote. We tell XK owners when replacement doesn't make financial sense.
Vetted Jaguar Specialists Our network includes 15+ vetted Jaguar specialists who work on XK engines daily - from AJ27 bore-wear diagnosis to AJ133 water pump replacement. No generalists - only Jaguar-specific expertise.
Part of Engine Finders JaguarEngine.uk is part of the Engine Finders family, the UK's leading engine replacement marketplace - giving you the research depth of an independent authority with a vetted route to action when you need one.
FAQ
XK
Frequently Asked Questions
Common Questions
1How much does an XK engine replacement cost in the UK?
An XK engine replacement costs between £3,000 and £10,000 supply-only depending on engine choice - the 4.0 AJ27 sits at the lower end (£3,000–£5,500), while the 5.0 AJ133 supercharged sits at the top (£6,500–£10,000) [JAG-QUOTE]. Labour adds approximately 12–18 hours at £65–£95/hr for an independent specialist. Use our diagnostic calculator to get a personalised estimate for your specific XK.
2Which XK engine is the most reliable?
The AJ133 5.0 V8 (2009–2014) is the most reliable XK engine. The 2009 facelift brought a revised timing chain tensioner design that resolved the weakness of earlier AJ-V8s, and the 5.0-litre unit has proven robust across the X150 range. The naturally aspirated 385bhp version is the sweet spot - simpler than the supercharged variant with fewer potential failure points.
3Which XK engine should I avoid?
Avoid the early AJ27 4.0 V8 (1996–2000) without documented history - these engines suffer from bore wear (blue smoke on throttle, misfires) and timing chain tensioner issues. If you're set on an X100, buy a 2003+ 4.2 car - the AJ34 is significantly more robust. For the X150, all engines are solid, but prioritise a 2009+ 5.0 car for the best reliability.
4Does the XK have timing chain problems?
Yes - pre-2009 AJ-V8 engines (AJ27, early AJ34) have a documented timing chain tensioner weakness. Cold-start rattle is the early warning sign. If you hear it, book an inspection immediately - ignoring it can cause catastrophic engine failure. Post-2009 5.0 AJ133 engines have a revised design and are much more robust.
5Is it worth replacing an XK engine?
It depends entirely on the car's value. A 2014 XKR-S worth £30,000–£35,000 with a £6,500–£10,000 recon cost sits at 20–30% of vehicle value - absolutely worth replacing. A 1998 XK8 worth £4,000–£5,000 facing a £5,000+ recon cost sits at over 100% of vehicle value - not worth it. If replacement cost exceeds roughly 60% of your car's market value, get a scrap valuation before committing. Use our diagnostic calculator for a personalised assessment.
6Which XK should I buy - X100 or X150?
Buy an X150 (2009–2014) with the 5.0 naturally aspirated V8 - it's the best-looking generation, the most reliable engine, and values are still £10,000–£20,000, which is remarkably low for a car of this quality. The X100 is a beautiful classic but the economics are tighter - only buy one if you're prepared for classic-car ownership costs.
7How do I find my XK engine code?
Your XK's engine code can be found in three places: (1) on the VIN plate inside the driver's door sill - the engine code is part of the VIN; (2) on the engine block itself - stamped on the front of the AJ-V8 block; (3) in your service documentation or V5C logbook. Our 15+ vetted Jaguar specialists can also identify your engine if you're unsure.
8XK vs XKR - which is more reliable?
Both use the same AJ-V8 engine family - the XKR simply adds a supercharger. The naturally aspirated XK has fewer components to fail (no supercharger, no intercooler), so it's technically the more reliable option. However, the XKR's supercharged V8 is robust when maintained - 2009+ examples with the 5.0 AJ133S have proven very reliable. Our honest advice: buy the XKR if you want the performance; the reliability difference is minor. Read the full comparison: XK vs XKR →
Next Steps
Ready to Make
a Decision?
Everything you need to choose with confidence.
Data. Honesty. Specialists. All in one place.
Explore
XK Generations
Compare the X100 and X150 side-by-side to find your perfect grand tourer. → Explore XK Generations
Explore NowDiagnose
My XK
Run our diagnostic calculator on your specific XK - real costs, honest verdicts, and a route to a vetted specialist. → Diagnose My XK
Start DiagnosisCompare
UK Specialists
Get matched with one of our 15+ vetted Jaguar specialists for a genuine XK engine quote. → Compare UK Specialists
Compare Specialists