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Jaguar V8 Engines 1997 - 2000 Preventive Tensioner Replacement

Jaguar engine - Tensioner Replacement

Jaguar’s 3.2 & 4.0 V8, known as the AJ-V8, was the first-ever eight-cylinder engine from that manufacturer. Designed in the mid-1990s by an all-Jaguar engineering team (including employees who worked on the previous twin-cam six), it proved to be a superb combination of lightness, torque, power, and fuel efficiency, the equal of anything from BMW or Mercedes.

In their zeal to reduce the weight of the valve train and related components as a way of improving fuel efficiency, the engineers under designed the AJ-V8's timing gear: in particular, the cam chain tensioners. These plastic components are part of the AJ-V8's single-chain design, a weight-saving alternative to the more robust double-chain approach Jaguar has used on most of its six-cylinder engines. (The new 4.2L version of the Jaguar AJ-V8 engine has double timing chains.)

As a result of their weak design and other factors like engine overheating or poor maintenance, the plastic cam chain tensioners on 1997 to 2000 V8 Jaguars began to experience stress fractures, and so did some of the plastic guides. While the cars were under warranty, many tensioners were replaced by Jaguar service departments with improved components.

In their Technical Service Bulletin No. X303-68 of February 2005, titled “Rattle From Engine on Start-up and Idle,” Jaguar states:

     This Technical Bulletin has been issued to address customer concerns of a rattle emanating from the engine on start-up and idle.

     Cause: Failure of a primary or secondary timing chain tensioner.

     Should a customer express concern, and the fault has been confirmed as a timing chain tensioner, new primary or secondary timing chain tensioners must be installed.

Cracked Tensioner

Engines subject to this problem include XJ8/XJR engines with the last six digits of their VIN numbers between 812256-F41862, and XK8/XKR engines with the last six digits of their VIN numbers between 001001-A24195.

Note that late in the 1999 model year the factory began installing upgraded plastic tensioners. These second-generation units are, to the best of our knowledge, more reliable than the originals.

In 2005, Jaguar introduced a third-generation metal-based tensioner kit. (See the photos at left.) We now use the metal-based third-generation tensioners exclusively when replacing cracked first- and second-generation Jaguar V8 tensioners.

When a plastic tensioner shatters or wears to the point the cam chain becomes loose, a rattling around can be heard in the cam area at the front of the engine. Usually this happens on start-up, when the engine is cold.

(Note that a rattling sound does not necessarily mean broken tensioners. There can be other causes that are not as drastic but nevertheless indicate trouble.)

On some occasions there is no rattling sound to serve as a warning. As the tensioners wear, the cam chains can become loose and eventually jump one or two teeth on the cam sprockets – usually on a cold start. If the chain jumps one tooth, rough running will be experienced. If it jumps more than one tooth, the valves on one block will contact the pistons, resulting in engine failure.

Servicing under warranty

Jagutek’s Jaguar service follows the manufacturer’s service guidelines using the specification of the vehicle Registration & chassis numbers. This means that if you service your Jaguar with Jagutek then you will receive a service, which is, in many ways, more detailed than your local Jaguar dealer. Changes to the Block Exemption laws mean that as an independent Jaguar specialist we can also service any Jaguar that is still under the Jaguar manufacturer's warranty. As our services follow the Jaguar warranty Guidelines your Jaguar is still covered under the manufacturer’s warranty along with a service book stamp. A service at Jagutek can also save you up to 50% when compared to your main Jaguar dealer’s service prices.

We regret your vehicle has to go to the main dealer for the warranty work to be carried out.

Jagutek’s quality, personalized Jaguar service is available for all Jaguar customers within Jaguar’s Warranty period as well as older Jaguar models whose warranty periods have expired. Out of Warranty when a service is carried out on your Jaguar, you will be contacted prior to any repairs being carried out & advise given.

Call us now to discuss your needs and our friendly staff will help you to keep your Jaguar running safely, reliably and within your maintenance guidelines

Each service is carried out according to Jaguar warranty specification and Genuine Jaguar parts, making sure that your warranty is protected at all times. Jagutek will help you PROTECT your warranty, to ensure your service book is stamped within the specific time and mileage. We provide a personalised quality service for all Jaguar customers for models within the Jaguar warranty period and also Jaguar models over 3 years old. No extra work is undertaken, until you the customer has agreed the work beforehand.

At Jagutek we are confident that your customer experience and our service will give you the high standards and reassurance you expect every time, so give us a call now and speak to one of our friendly advisers who will assist you with your Jaguar needs.

We offer very competitive service prices with fixed cost services available on all post 1994 Jaguars. Changes to the Block Exemption laws mean that as an independent Jaguar specialist we can also service any Jaguar that is still under the Jaguar manufacturer's warranty.

warningIf upon start-up you notice a rattling sound from your 1997-2002 Jaguar V8 engine, or unusually rough running, turn off the engine immediately and DO NOT restart it. Have the car towed to a Jaguar specialist service facility for inspection.

Cracked Tensioners

The AJ-V8 was first installed in the XK8/XKR starting in 1997, and then in the XJ8/XJR (and Vanden Plas models) starting in 1998. Tensioner failures have been experienced by owners of V8 models through to the 2002 model years.

Jaguar Cars has instructed their dealer service shops to listen for the telltale rattling sounds during routine service visits. When the cars were under warranty, rattling tensioners, or failed engines due to tensioner breakage, would be replaced with beefed-up second-generation plastic tensioners at no charge to the owner.

Jaguar Cars will NOT cover repair of the tensioners, or associated engine failures, on cars that are out of warranty -- and of course all those model years are now past their factory warranty expiration.

Some third-party extended warranties cover tensioner replacement and even engine rebuild on tensioner failure. Check with your warranty provider. If you would like us to do a tensioner replacement under third-party warranty, please supply us with contact information about your warranty provider before we start the job.

We recommend that if your XJ8/XK8 has passed 35,000 miles, you take preventive action and have the tensioners inspected. If they are cracked, have them replaced before they fail.

While many cars make it to higher mileage without failure, a significant number do not. We don't know the exact number because the factory is keeping it confidential, but we are aware of the problem through extensive service work on V8 Jaguars, and from our discussions with jaguar parts suppliers.

Jaguar dealer service departments will not replace the tensioners before failure under warranty without the engine displaying obvious symptoms (e.g., rattling noises). And if you own a 1997-2000 Jaguar, your factory warranty has expired by now.

preventive maintenance

As a preventive maintenance operation, Jagutek service department, can replace your timing gear with improved components. At Jagutek, we use exactly the same parts the Jaguar dealers do, and having done so many V8 timing gear upgrades, we are highly expert and efficient at this procedure. Our parts and labour are guaranteed for one year.

Tensioner replacement of the Jaguar V8 is a prudent investment because the cost of inspection and replacement (if required) is reasonable, and the car is in almost all other respects exceptionally reliable. (Early XJ8s and XK8s have a few other, less serious, weak points that can be remedied at the same time as the tensioners. See the sidebar at left.)

For a limited time we are offering an upper tensioner inspection for eight-cylinder Jaguars from 1997 - 2002 model years. At no charge we will remove the right-bank valve cover and inspect the secondary tensioner on that bank.Only available at service time. You will be able to see the tensioner's condition for yourself at that time.

Our workshop offers a replacement package for replacement of the secondary tensioners, primaries, guides, all chains, and seals. We only use Jaguar's third-generation metal tensioners.

Should you elect to replace your tensioners, make an appointment and we normally have a 48-hour turnaround. Our 12-month, unlimited mileage warranty will apply to all parts and labour.

Could you experience the problem with the new tensioners after replacement is carried out? Jaguar's third-generation replacement tensioners are far more robust in design and, though it is too soon to ascertain their longevity with complete certainty, we are confident that they will provide a “one-time” solution to the problem. One thing we are certain of is that all parts and labour we provide are covered under our one-year, unlimited mileage warranty.

Broken Chain

If your V8 Jaguar has low mileage and its original tensioners, follow these precautions to maximize original tensioner life: Avoid letting the car sit for several days if possible. (This can cause stretched chains to “sag” and then jump a tooth or two under the torque of engine start-up.) Instead, drive it daily if you can. Avoid driving short distances on a cold engine – let it warm up before shutoff by driving at least 15 minutes if possible.

Maintain the car faithfully. We recommend oil and filter changes every 5,000 miles (as opposed to the manual’s 10,000 mile recommendation), using 10W40 fully or semi-synthetic.

Your original tensioners MAY last longer if the above precautions are taken, but due to the nature of their design, we can make no guarantees.

If you hear a rattle in the front of the engine, stop the car immediately and have it towed to a Jaguar service facility. Similarly, if the engine is running very roughly or refuses to start, have it towed. In either case, DO NOT TRY TO RESTART THE ENGINE.

If the worst happens and the valves contact the pistons due to tensioner failure, all is not necessarily lost. Whereas some places recommend engine replacement (at a cost of £5,000 or more), we can repair an engine that has suffered tensioner failure and subsequent valve damage on one bank for less than under half that price.

Investing in preventive replacement of the tensioners will remedy this excellent engine’s only serious flaw. If proper maintenance is carried out and the car is not abused, your V8 Jaguar engine should be as reliable and long-lived as its famously durable 6-cylinder ancestor.

An ounce of prevention is worth a pound of cure