Car Doctor Q&A: Is it Worth Replacing a Cam Chain Tensioner on a Jag?

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Yeah, replacing a timing chain tensioner on a Jaguar XK8 is going to be expensive, but look on the bright side: It’s not as expensive as the transmission that’s going to fail about 22,000 miles from now.

Q. My fun car is a 1998 Jaguar XK8, the car is in excellent condition with only 51,000 miles on it. At my last yearly tune up, my mechanic mentioned that I should think about changing the plastic cam chain tensioner which apparently will fail at about 60,000 miles. This is an expensive job and I’m wondering if this is really necessary considering that I only use the car around town and on short drives?

A. The timing chain tensioners in this model V-8 were plastic and with a combination of heat and friction can fail. The first sign of failure is a rattling noise on engine start-up. Over time the rattle will be heard at idle cold or hot. In the most extreme case the tensioner will completely fail causing the timing chain to jump, which can cause pistons and valves to collide.

Jaguar has updated this tensioner twice the last being the most robust. The final version of this tensioner should last the life of the engine. You are correct, the repair is expensive, about a days labor and $700 for the timing chain guides and tensioner. In addition there may be some other components/parts that will need replacement.

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As expensive as this repair is, if the part fails, the resulting engine damage could be well over $10,000. As frugal/cheap as I am, if this were my car I would have the chain tensioners and guides replaced.

John Paul is public affairs manager for AAA Southern New England. A certified mechanic, Paul tests dozens of new cars each year and also hosts a radio show on AM 950 and 550.