AJ133 Timing Trouble – JLR 5.0 V8 Engine Focus

The AJ-V8 first went into production in 1996. It was a 4.0L, eight cylinder engine which was set to replace both designs available at the time from Jaguar. In the following years they introduced a 3.2, 3.5, 3.9, 4.2 and 4.4 versions until 2009 when the 5.0L, AJ133, version was created. It was first introduced into Jaguar applications in 2010 and was used predominantly up until December 2024, when JLR discontinued most of their ICE vehicles ready for an all electric line up.

Early 5.0L models suffered a common timing chain issue. The guides rails were not strong enough. The metal part of the guide rails were made of aluminium and this was weaker than the tensioner, made from steel. As the tensioner was stronger it would dig into the guide and wear it down over time.

This reduces the amount of tension the guide rail has on the chain and will eventually lead to the chain skipping. Ultimately, this was addressed by JLR in 2015 and they released a revised version of the guide rails with a steel indent, allowing the tensioner to sit comfortably without causing damage.

While this should ease the minds of would-be buyers, there has been continued examples of timing chain failure from 2015 onward. In one such case a driver found excessive carbon and sludge build up around the tensioner, restricting oil flow and preventing full tension.

Overall, it seems that JLR only fixed one part of what is a bigger issue. With multiple people still reporting timing chain failure, as a result of their chain skipping, it appears that the fix to the chain guides isn’t enough. If you want to read more about the continued timing chain failure in these vehicles I would recommend this article from Robison Service>

In 2012, JLR released the 3.0 V6 derivative of this engine, the AJ126. They nullified the final two combustion chambers, however instead of simply cutting that part off the engine they left the outer casting the same. This unorthodox approach meant that no changes to the engine mounting or shell of the vehicle were necessary.

To ensure the timing was correct they also utilised a split-pin crankshaft. This seperates the adjoining connecting rods so that each cylinder fires every 120 degrees of rotation, instead of 90 degrees that a standard V8 would run at. By 2020, JLR had completely phased out the V6 amalgamation in favour of the turbocharged ingenium.

Due to the similarities, both the AJ133 and AJ126 use the same timing chain system. There is only one minor difference and that appears in the auxiliary chain drive. On the 5.0 version a tensioner guide and guide rail are used. The 3.0 version uses only the tensioner guide, using a balance weight sprocket in place of the guide rail.

V6 | 3.0 | AJ126

V8 | 5.0 | AJ133

GTCK244 is our timing chain kit for the AJ133 and AJ126. It features both tensioner guides needed for either application, eliminating the need for two separate kits.