Jaguar AJ-V8 Family (Gen I)

AJ26 / AJ26S / AJ27 / AJ27S / AJ28

The AJ26S is a supercharged version of the AJ26, and the AJ27S is a supercharged version of the AJ27.

The AJ27 added continuously variable valve timing.

Timing chain:
- Plastic timing chain guides
- Plastic timing chain tensioners – 1st generation parts may rattle, but 2nd generation parts may fail silently. 3rd-generation parts (introduced in 2003) are metal and are the recommended fix. If the tensioners were replaced around 2003-2004, check that they’re the metal parts. If they were replaced before 2003, then plan on upgrading them to the metal ones.
Older engines may suffer from head gasket failure; a coolant chemical test is recommended as part of a prepurchase inspection
Cooling system:
- Early water pumps were prone to broken impellers
- Plastic thermostat can break
Loss of oil pressure in high-G cornering can eventually cause oil starvation and failure of the bearings in cylinder #1. Frequent oil level checks are recommended.

Vehicles produced prior to MY2000: Prone to failure of the Nikasil cylinder liners. Failures were generally caused by fuel with high sulphur content or a lot of drives where the engine was not allowed to heat up fully. Fuel today has much lower sulphur content than in the 90s; generally, if the engine is still working fine, then you shouldn’t have any issues – provided you take the car out for longer drives and allow it to get fully up to temperature. Many vehicles have had their engines replaced with ones that have iron liners, but many others are still using the original engine.

This section is still under construction, and may not have complete information.

The AJ35 added variable valve timing and electronic throttle control.