About the jaguar XJ (X351)
The X351 XJ looks like a rapid departure from the previous XJ model in terms of design, but actually uses the same underpinnings as they were highly advanced for the time. The bonded aluminium construction allows for significant weight savings in comparison to a steel bodied car improving both fuel economy and emissions. Like other top-end executive cars, the XJ comes loaded with technology inside and out, because of this, specialist equipment is required to work on them.
With our experience at K Motors and our advanced diagnostics systems, we are able to find and fix any faults on the XJ whether they are mechanical or electrical.
We have put together a list of some of the more common issues found on the XJ (X351) with symptoms and the solutions required to resolve them.
Timing Chain, Tensioners and Guides | Early 3.0 Supercharged V6 & 5.0 V8
A well-known problem with early 5.0 V8 and 3.0 supercharged V6 models is the timing chain jumping. This is caused by a design flaw in the tensioners and guides. Basically, the piston used on the tensioner which hits the timing chain guide is made of hard steel whereas the back of the guide is made of aluminium, the tensioner butts up against the aluminium button on the guide slowly wearing it away over time.
If you’re lucky, symptoms may start with a rattle on cold start or a restricted performance warning on the dashboard, but this is not always the case, sometimes they will spontaneously fail leaving no option other than a replacement engine or a potentially more expensive full rebuild including valves and pistons. Preventative maintenance is basically limited to regular oil changes but if you have a high mileage model and the chain, tensioners and guides have not yet been replaced, you might want to have this done sooner rather than later.
It is hard to pinpoint the model year where this issue was resolved as there were revisions to the timing chain design in 2012, 2014 and 2016.
Water Pump | 3.0 Supercharged V6 & 5.0 V8
Water pumps on 5.0 V8 and 3.0 Supercharged XJ models are prone to failure, sometimes they can fail in less than 20,000 miles. This is because coolant gets inside the bearing housing corroding the water pump bearing. This stops the impeller shaft from being supported properly causing excessive wear of the mechanical flat face seal of the pump allowing water to escape.
Symptoms of this will likely be a low coolant level warning message and traces of a coolant leak around the water pump pulley. Luckily the water pumps on both the V6 and V8 XJ are fairly easy to access at the front of the engine. We also recommend replacing the small coolant pipe that connects to the pump at the same time as it needs to be removed to replace the pump and has very fragile plastic connections that will likely break upon removal.
Coolant Leaks | 3.0 Supercharged V6 & 5.0 V8
Sadly, the water pump is not the only part of the cooling system that can fail on petrol XJ models, many of the hoses and pipes used for coolant delivery are of a plastic design, unfortunately these can crack and fail. Replacing them one at a time as they fail is not a particularly efficient approach and could result in you being in and out of the garage, and as such we recommend that all plastic coolant hoses are replaced if one has failed.
Crankshaft Failure | 3.0 V6 Diesel
Whilst it not as widely reported as on the old 2.7, the 3.0 V6 diesel engines can suffer from crankshaft failure, this can range from spun main bearings starving the bottom end of oil to the crankshaft actually snapping.
Symptoms could be a knocking bottom or even a completely seized engine. In either case, we would replace the engine with a bare unit sourced from Jaguar as the damage will be uneconomical to repair.
Gear Selector Stuck Down | All Models
The XJ uses the same electronic rising gear selector as the original XF. which pops out of the centre console when the ignition is switched on. Whilst this is a nice design touch, it has led to some problems down the line. Unfortunately, there is an issue where the gear selector can get stuck down in the console meaning when the car is switched on, it is stuck in Park.
The fix for this fault if it is not a just weak battery causing an issue with the electrics is to fit and program a new selector unit and this is not a cheap part. This issue is not as widely reported in XJ models as it is in the XF and later models generally seem largely unaffected by this issue but it has been known to pop up occasionally.