Timing chain tensioners are probably the biggest vulnerabilities 1997-2004 Jaguar V8 engines. The tensioners get old, and the plastic face that touches the chain gets brittle and breaks. When that happens the chain flops around excessively, until it fails.
There is no warning of this impending failure from outside. The only way to know if your guides and tensioners are good, is to remove the cam covers and inspect them. Inspection – if they are good – is a three-hour job. Replacement of the upper tensioners – if needed – is a day’s work. Replacement of the lower chain guides is a much bigger job, most often two days of work.
All those costs pale when compared to the bill for repair, if the chain breaks. That will often run $8-10,000.
The lesson to be drawn from this: Check your tensioners, and deal with them before they fail. New tensioners are a few hundred dollars, plus the labor to put them in. It's a small price to pay for security.
Robison Service takes Jaguar service from all over the northeast. We've been catering to British car lovers for over 20 years. Visit us online at www.robisonservice.com