Cam chain tensioner

I've got a 2001 (UK W-reg) XJ8 3.2 with 91,000 miles on the clock.
Of course, I've heard about the risks of the cam chain tensioner failing
(and I believe there's a water pump weakness, too, is that right?).
Can anyone give me an idea of what the actual chances of a tensioner failure are? I mean, is it pretty well guaranteed to happen to every car that doesn't have the new type fitted? Or one in ten?
I ask because it's a damned expensive job to get a new one fitted, so I need to make a judgement on whether the costs outweigh the risks.
Also, do I need to worry about the Nikasil problem?
Any thoughts gratefully received.
Thanks,
SteveT
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Sorry, guys, I realise I should have searched the Google archives first.
Still, if anyone would like to summarise the current thinking on the situation, I'd be most grateful.
Thanks,
SteveT
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I don't own a V8 Jag, but I've been thinking about it (I have an XJ40 and a V12 XJS). The owner of the independent specialty shop where I have my Jags serviced told me it is an issue that WILL occur sooner or later in early V8's (not likely prior to about 50K miles) and that it costs about US$1800 to fix. He says it generally gives ample warning before a catastrophic failure, that he can listen for a growl at the front of the engine that tells him the failure is in the early stages. He does not tell his customers to automatically make the change, but to be aware that it has to be done and budget for it, meanwhile checking for strange engine noise. He suggested I look for a 2002 model to avoid the problem.
But, I think the chain tensioner problem was corrected late in the 2001 model year, so you might want to check with a Jaguar dealer (or search the internet) to find out what serial number marked the change, perhaps your car already has the fix.
I can't help with the other issues, but I'd assume a Nikasil problem would show up prior to 91K miles; also, if you DO have the tensioner work done, seems prudent to replace the water pump whilst it's torn apart... chances are the water pump has already been changed considering your mileage.
Steve Thackery wrote:

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This is wrong information. There have been many documented cases (www.jag-lovers.org) of tensioners giving out with absolutely no warning, no noise or anything else that might indicate impending doom.
In addition it may cost $1800 to replace the tensioners before they let go, but if you didn't catch them, it will cost WAAAY more, as then engine may well be trashed (depends how many cosgs it jumps). At 90K miles, you are living on borrowed time if they haven't been replaced. Get the tensioners replaced with 3rd generation metal ones, and whilst you're there do the water pump with a metal impellor and the thermostat. If the car is a keeper, you should do this work. If you plan on selling it soon, then don't worry, it will someone else's problem (although if it was me I would reject any potential AJ8 engined jag that hadn't had this work done by now)...
- Barney
Prior owner of an XJ6, an 00 S-type 4.0 with a Nikasil engine (yes Jaguar did fit some S-types with Nikasil engines) an 01 S-type 4.0 and an '05 x-type, and soon to be owner of an 02 XKR....

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Does the above apply to a 2000 V8 'S' Type as well?
Richard L
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Has anyone any idea how much it will cost here in the uk?
Any recommendations on who can do it in the west/north midlands area?
I have a 99 'V' XK8 with 52k miles. The tentioner has not been replaced yet!

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I can't help with the North and West question, but here is how the job added up for me:
Water pump: 48.93 Thermostat: 26.17 Crankshaft seal: 16.71 Secondary chains: 66.90 Bolt: 4.25 Chain tensioner: 47.81 Chain guides: 23.16 Chain tensioner: 53.56 Chain tensioner: 47.81 Hex bolts: 3.60 Timing seal: 10.4 Insulators: 61.88 Primary chains: 64.96 Timing seal: 10.40
Total parts: 486.64
Labour: 578.56 (9.98 hours at 58 per hour)
Total without VAT: 1065.10 Total inc VAT: 1251.50
I used Elite and Performance Jags at Derby (www.eapj.co.uk)
SteveT
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