Should I change all XKR tensioners or just top ones?
Discussion
What do you recommend?A lot will depend on how many miles the car has done, how it has been used, if it's ever been overheated and if the service history is complete.
The primary tensioners do not fail in the same way as the secondaries as they don't directly contact the timing chains.
The main criteria for deciding what needs to be done is how much - if at all - the chains have stretched and if there is any evidence of unususal wear patterns on the sprockets and guides or any noise from the chains when the engine is running.
If the engine is clean inside with no evidence of wear on the timing gear, the primary and secondary chains are clean and tight and the tensioner pistons have not extended too far on their travel then I'd say it's probrably OK just to change the secondary tensioners for the metal bodied type.
If there's evidence of skimped servicing - usually shown by a glaze of brown deposits on the engine internal surfaces - and any signs of bright metal wear on the sprockets or groves in the tensioner slippers and guides, or if you can feel any slack at all in the chains then the safest option is to go for a full primary and secondary chain and tensioner change.
An experienced mechanic will be able to remove the cam covers and have a good look inside the engine and assess what state the timing gear is in within an hour.
However, if he's playing safe - most mechanics will, especially as they are obliged to give a warranty on any work they do and it's not their own money they are spending - and he's looking for work it's likley he'll recommend the whole job is done to avoid any comebacks on him later.
Edit to add:
If it's just the secondary tensioners you need to change and you're reasonably competent it's not a difficult job at all. You can hire the necessary timing tools from the JEC, the components cost about £100 and it shouldn't take more then a morning to do.
The primary tensioners do not fail in the same way as the secondaries as they don't directly contact the timing chains.
The main criteria for deciding what needs to be done is how much - if at all - the chains have stretched and if there is any evidence of unususal wear patterns on the sprockets and guides or any noise from the chains when the engine is running.
If the engine is clean inside with no evidence of wear on the timing gear, the primary and secondary chains are clean and tight and the tensioner pistons have not extended too far on their travel then I'd say it's probrably OK just to change the secondary tensioners for the metal bodied type.
If there's evidence of skimped servicing - usually shown by a glaze of brown deposits on the engine internal surfaces - and any signs of bright metal wear on the sprockets or groves in the tensioner slippers and guides, or if you can feel any slack at all in the chains then the safest option is to go for a full primary and secondary chain and tensioner change.
An experienced mechanic will be able to remove the cam covers and have a good look inside the engine and assess what state the timing gear is in within an hour.
However, if he's playing safe - most mechanics will, especially as they are obliged to give a warranty on any work they do and it's not their own money they are spending - and he's looking for work it's likley he'll recommend the whole job is done to avoid any comebacks on him later.
Edit to add:
If it's just the secondary tensioners you need to change and you're reasonably competent it's not a difficult job at all. You can hire the necessary timing tools from the JEC, the components cost about £100 and it shouldn't take more then a morning to do.
Edited by Jaguar steve on Friday 28th November 16:28
Thanks for your comprehensive post 
I have so far been given the following quotes, both by Jaguar specialists - although neither has seen the car yet...
1. £1100 to change all tensioners, water pump (if necessary) and thermostat
2. £1650 to do above or £512 to change water pump, top tensioners and thermostat
The second chap hasn't come across a problem with the lower tensioners and believes I would be ok with just the top ones replaced - at least until he has seen the car. The top quote seems good value (and about what I expected) although he is some distance from me...
Any thoughts?
I have so far been given the following quotes, both by Jaguar specialists - although neither has seen the car yet...1. £1100 to change all tensioners, water pump (if necessary) and thermostat
2. £1650 to do above or £512 to change water pump, top tensioners and thermostat
The second chap hasn't come across a problem with the lower tensioners and believes I would be ok with just the top ones replaced - at least until he has seen the car. The top quote seems good value (and about what I expected) although he is some distance from me...
Any thoughts?
The key is seeing the car IMO.
Only once the waterpump, chains and tensioners have been looked at by somebody who has seen several examples and has experience with the V8 engine can make a sensible assesment be made.
It shouldn't take more than an hours labour to whip off both the cam covers and have a look. You might even find the tensioners have already been changed.
The waterpump needs to come off and the impellor vanes checked for errosion or damage if it's the earlier type (metal gasket = older, black rubber gasket = revised) design. It's not always safe to assume that if the car warms up quickly and the temperature gauge reads exactly half way between hot and cold there's not a problem lurking withing the cooling syatem.
On an older car it will do no harm and bring some peace of mind to change the thermostat once the cooling system is drained down to remove and check the pump anyway. Fresh coolant and a new thermostat is never a bad thing
Timing gear on these engines usually fails or wears because either oil changes have been skimped - the servicing requirement is very marginal at 10000 miles anyway - the engine has been overheated or the earlier plastic bodied secondary tensioners have either cracked or the slipper delaminates from the piston.
If none of this applies to your car, then you might only have to change the secondary tensioners as a precaution. Whatever you do, you'll have to get the car looked at.
I've heard some Jaguar indies are happy to change just the secondary tensioners whilst others insist on changing all the chains, tensioners and guides - either because they find it's a genuine case of wear throughought, or they are covering their arses, or need more work booked in that week.
You might want to consider joining the JEC. There's a useful XK8/R forum and you'll have free access to expert technicial advice. There's always several independents advertising in the magazine too.
Only once the waterpump, chains and tensioners have been looked at by somebody who has seen several examples and has experience with the V8 engine can make a sensible assesment be made.
It shouldn't take more than an hours labour to whip off both the cam covers and have a look. You might even find the tensioners have already been changed.
The waterpump needs to come off and the impellor vanes checked for errosion or damage if it's the earlier type (metal gasket = older, black rubber gasket = revised) design. It's not always safe to assume that if the car warms up quickly and the temperature gauge reads exactly half way between hot and cold there's not a problem lurking withing the cooling syatem.
On an older car it will do no harm and bring some peace of mind to change the thermostat once the cooling system is drained down to remove and check the pump anyway. Fresh coolant and a new thermostat is never a bad thing
Timing gear on these engines usually fails or wears because either oil changes have been skimped - the servicing requirement is very marginal at 10000 miles anyway - the engine has been overheated or the earlier plastic bodied secondary tensioners have either cracked or the slipper delaminates from the piston.
If none of this applies to your car, then you might only have to change the secondary tensioners as a precaution. Whatever you do, you'll have to get the car looked at.
I've heard some Jaguar indies are happy to change just the secondary tensioners whilst others insist on changing all the chains, tensioners and guides - either because they find it's a genuine case of wear throughought, or they are covering their arses, or need more work booked in that week.
You might want to consider joining the JEC. There's a useful XK8/R forum and you'll have free access to expert technicial advice. There's always several independents advertising in the magazine too.
[quote=Jaguar steve]JEC is The Jaguar Enthusiasts' Club - www.jec.org.uk.
You'll get free advice from the various technicial experts in the club - some of whom run their own specalist Jaguar garages in a mutually beneficial arrangement, and there's some interesting forums too.
You don't get anything for nothing though, but I'd say it's worth locating an independent through the club and paying an hours labour or so for sombody to look at the tensioners/chains and water pump.
For what it's worth, the engine internals were extremly clean on my 80k, 2000 XJ and all the chains, sprockets and guides were fine - but both the secondary tensioner bodies had cracked, one to the point where the entire assembly fell apart when I took it off. These really are a weak point and must be changed IMO
You'll get free advice from the various technicial experts in the club - some of whom run their own specalist Jaguar garages in a mutually beneficial arrangement, and there's some interesting forums too.
You don't get anything for nothing though, but I'd say it's worth locating an independent through the club and paying an hours labour or so for sombody to look at the tensioners/chains and water pump.
For what it's worth, the engine internals were extremly clean on my 80k, 2000 XJ and all the chains, sprockets and guides were fine - but both the secondary tensioner bodies had cracked, one to the point where the entire assembly fell apart when I took it off. These really are a weak point and must be changed IMO
If you are thinking of joining a forum and do not actually want to hire tools the xkec.co.uk is the best for the XK8/XKR. The JEC and JDC cover all the models. I would not consider changing just the top tensioners as I have seen damaged guides and heard of engine failures caused by these rather than tensioners. Good idea if not already done to change the water pump and thermostat at the same time.
notax said:
Thanks. JEC? Can you tell me a little more? I'm guessing the free technical advice wouldn't include looking at the car and telling me what it needs? 
You can see there the nearest region is to you here
http://www.jaguar-enthusiasts.org.uk/regions.html
And join the JEC from here
http://www.jaguar-enthusiasts.org.uk/register.html
notax said:
Norman, thanks for the TL Jaguar recommendation My car is booked in to have all the tensioners, thermostat and water pump replaced next Friday. Long drive but hopefully worthwhile!
Please to see that, ask Tom about the re-map and de-restriction as well. My car is booked in to have all the tensioners, thermostat and water pump replaced next Friday. Long drive but hopefully worthwhile!Anthor thing he could do while he is doing the tensioners is fit a larger bottom pully, that will make the supercharger turn 15% faster giving more power thoughout the rev range.
I will be seeing him this morning (Saturday) to collect my car, he has just fitted a 4.2Lt engine to my 4.0Lt XKR
NormanD said:
notax said:
Norman, thanks for the TL Jaguar recommendation My car is booked in to have all the tensioners, thermostat and water pump replaced next Friday. Long drive but hopefully worthwhile!
Please to see that, ask Tom about the re-map and de-restriction as well. My car is booked in to have all the tensioners, thermostat and water pump replaced next Friday. Long drive but hopefully worthwhile!Anthor thing he could do while he is doing the tensioners is fit a larger bottom pully, that will make the supercharger turn 15% faster giving more power thoughout the rev range.
I will be seeing him this morning (Saturday) to collect my car, he has just fitted a 4.2Lt engine to my 4.0Lt XKR
notax said:
I've seen the bottom pulleys for sale - is the difference that noticeable? I think my next investment has to another Road Angel or similar - the XKR is my quietest car by miles and I can see myself getting into trouble by underestimating my speed...
I do have a spare one, I'll take it over to Tom for Friday, be no extra labour charge to fit if he does it the same time as the tensioners.
NormanD said:
groomi said:
I bet you got a good price for your old 4.0L engine? High demand for these when things go bang!
I've still got it, hadn't had time to see about selling yet, how much do you think its worth?The alternative was fitting an engine from a crash damaged or broken up car. These were not plentiful in supply and would still have cost me about £1500 + fitting despite having no history at all. The thought of spending approx £4k after fitting for an engine which may be about to go pop anyway wasn't enticing.
Your in the position of having an engine for sale, which you could photocopy all the relevant service history and include with it. This would mean the buyer knows the mileage and history of the engine including knowing that it has the phase 3 tensioners fitted (presumably). I think offered up for sale with no particular rush to get rid of it, could result in a tidy sum - at a guess £3k or so...
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