Jaguar XK AJ133/AJV8 Specialist Engine ReplacementCompare Quotes

The 4.2L AJ-V8 is very reliable when its timing chain tensioners are upgraded. The 5.0L Gen III offers more power but adds oil pump failure risks. Both are good choices with different trade-offs.

• 4.2L's main weakness is plastic timing chain tensioners - upgrade to steel-caged units
• 5.0L delivers 385bhp (or 510bhp supercharged) but has oil pump drive failures
• 5.0L engines also suffer cylinder bore scoring at higher mileages
• 4.2L generally cheaper to rebuild - from £3,895 vs 5.0L from £4,500

A rebuilt 4.2L XK engine costs £3,895-£5,500 supply only. XKR 5.0 supercharged units run £5,900-£7,800. Add £1,200-£2,200 for professional supply and fit through a specialist.

• 4.2L naturally aspirated: £3,895-£5,500 (AJ34, 5G codes)
• 4.2L supercharged (XKR): £5,500-£7,500 (AJ34S)
• 5.0L naturally aspirated: £4,500-£6,200 (508PN)
• 5.0L supercharged (XKR/XKR-S): £5,900-£8,500 (AJ133/AJ133S)
• Supply & fit adds £1,200-£2,200 depending on XK variant

Rattle on startup points to timing chain tensioner failure. Rattling from the front of a supercharged XKR suggests coupler wear. Blue smoke indicates valve stem seals. Knocking means bottom end bearing failure - stop driving immediately.

• Rattle on cold start that lasts 1-2 seconds = timing chain tensioners failing
• Rattling noise from engine front that changes with revs = XKR supercharger coupler wear
• Blue smoke on startup = valve stem seals (progressive, not catastrophic)
• Persistent knocking = rod or main bearing failure - do not drive
• Check engine light with VVT codes = solenoid failure, often repairable without full replacement

Not a direct swap. You would need the XKR ECU, complete engine harness, cooling system upgrades, transmission modifications, and a different differential. It is prohibitively expensive.

• Different ECU mapping - XKR uses supercharger-specific calibration
• Engine harness is not compatible between naturally aspirated and supercharged
• Cooling system requires upgrades for supercharger heat rejection
• Transmission and differential ratios differ between XK and XKR
• Most specialists recommend selling your XK and buying an XKR instead

Jaguar does not specify a timing chain replacement interval. However, the plastic tensioners typically fail between 50,000-85,000 miles. Preventative replacement is strongly recommended on all AJ-V8 engines.

• Tensioner failure symptoms: rattle on startup, metallic noises, check engine light
• Failed tensioners allow chain to skip teeth - causes valve and piston contact
• Preventative replacement costs £1,800-£2,800 at a specialist
• Post-failure repair often costs more than a rebuilt engine
• Upgraded steel-caged tensioners should be fitted during any replacement

The 5.0L Gen III (2010-2012) has the worst reputation due to oil pump drive failures (Recall JAG-19V-005) and bore scoring. The 4.2L is more robust but still needs timing chain tensioner upgrades.

• 2010-2012 5.0L cars most affected by oil pump failure - check recall was performed
• 4.2L timing chain tensioners fail - budget for preventative replacement on any used XK
• XKR supercharged models have additional coupler wear costs (£700-£1,200)
• Late 4.2L (2008-2009) and post-recall 5.0L (2013-2014) are safest bets
• Full service history is essential - missed oil changes accelerate all failure points

With proper maintenance and preventative timing chain work, an AJ-V8 can reach 150,000-200,000 miles. However, most original engines fail between 60,000-100,000 miles due to tensioner or oil pump failure.

• Well-maintained 4.2L engines regularly exceed 150,000 miles after tensioner upgrade
• 5.0L Gen III with recall performed can also reach high mileages
• Oil changes every 5,000-7,000 miles (not the 15,000-mile Jaguar schedule) extend life
• Most XK engines on replacement market have failed between 60k-100k miles
• Rebuilt engines with upgraded components often outlast original factory units

Replace if timing chain failure caused valve/piston damage, cylinder bore scoring is present, or crankshaft has failed. Rebuild only for minor issues like valve stem seals or head gasket failure without other damage.

• Catastrophic failure (snapped chain, seized oil pump) = cheaper to replace than rebuild
• Bore scoring on 5.0L = replacement with warranted unit is safer than reboring your block
• Minor oil leaks or valve seals = rebuild is viable and more cost-effective
• Rebuilt replacement engines come with 12-month warranty - rebuilds of your engine often do not
• Most specialists recommend replacement over rebuild for XK V8s

No. Every Jaguar XK sold in the UK (both X100 XK8 and X150 XK/XKR) uses a petrol V8 or, on the earliest XK8 models, a 4.0L straight-six. There is no diesel XK.

• X100 XK8: 4.0L straight-six (AJ16) or 4.0L/4.2L V8 (AJ26/AJ27/AJ34)
• X150 XK: 4.2L or 5.0L naturally aspirated V8 (AJ34/5G, 508PN)
• X150 XKR: 4.2L or 5.0L supercharged V8 (AJ34S, AJ133/AJ133S)
• All Jaguar XK engines require 5W-20 or 5W-30 fully synthetic oil
• No diesel variant was ever produced for any global market

Jaguar specifies 5W-20 fully synthetic oil for the AJ-V8 family. Change every 5,000-7,000 miles for maximum protection - ignore the 15,000-mile service schedule if you want the engine to last.

• 5W-20 fully synthetic is the manufacturer specification for all AJ-V8 engines
• Oil capacity is approximately 7.3 litres (7.7 quarts) for the V8
• 5W-30 is also acceptable for higher-mileage engines or warmer climates
• Extended oil change intervals contribute to timing chain tensioner failure
• Use genuine Jaguar filters or high-quality OEM equivalents