7 year service
Discussion
In reality, the plugs can go 100k, and in most other brands the plugs similar to these are fit for life of engine (100k miles).
The plugs only 'need' changing if misfire counts are present on diag system or perhaps customer comments the engine doesn't fire clean at cold start.
I think that the best end result to decide to, or not to change is a pragmatic discussion of facts between service provider and client and between them they decide.
On V8 change cos the book says so at 7 year interval, IMO - nah... But at 7 year if + 100k miles, + LOTS of cold starts in lifetime + lots of track days - perhaps...
On V12 change cos book says so at 7 years - perhaps yes, this is because at this age the breather circuit valves are likely in need of renewal and both plug and breather circuit valve change is a manifold off job.
Never seen a plug removed from an engine at 7 year interval yet that you would inspect and say... Lucky we changed that, its knack'd..!
The plugs only 'need' changing if misfire counts are present on diag system or perhaps customer comments the engine doesn't fire clean at cold start.
I think that the best end result to decide to, or not to change is a pragmatic discussion of facts between service provider and client and between them they decide.
On V8 change cos the book says so at 7 year interval, IMO - nah... But at 7 year if + 100k miles, + LOTS of cold starts in lifetime + lots of track days - perhaps...
On V12 change cos book says so at 7 years - perhaps yes, this is because at this age the breather circuit valves are likely in need of renewal and both plug and breather circuit valve change is a manifold off job.
Never seen a plug removed from an engine at 7 year interval yet that you would inspect and say... Lucky we changed that, its knack'd..!
drmw said:
With some manufacturers it's done to make sure the buggers can still be removed & are not seized
That's a good point. The V8 is flat washer type so less chance of not coming out when asked, V12 is taper seat and that construction can sometimes be more prone / possible to get stuck in, but not seen a case of this before either, but sure it can happen.
Jockman said:
Without doubt 
Don't you start Jockers or this will go OT and Bob will be saying how sad he is when I start cussing and Peter in a drunken stupor posts obscene pics.Anyway you're in Turkey so why aren't you in the Casbah watching some fat bird wiggling her tummy. ?
BTW at least some good advice from MG.
Not AM, but related to the plugs.
I have another car that uses exactly the same plug type as my GT.
I just replaced them as the car was starting to misfire and stalled once.
When I removed the plugs, (V6 and manifold off job) I found them to be the original factory fitted plugs.
These had been in there for 12 years and have covered almost 160K abusive miles.
They were royally f*ked, I've never seen a set of plugs so bad, yet they had only just started to exhibit faults.
Theses plugs are also buried deep in the engine under individual coil packs so essentially very much the same scenario as the AM engine.
So the point here is 12 years, 160K miles and every start will be a cold one in that motor.. lol
Plugs are not as delicate as we are led to believe by the main service agents.
As BR pointed out if there are no codes flagged then why change them?
Of course if the manifolds are coming off anyway for other work then yes take the opportunity, so long as you only pay £50 a set ;-)
I have another car that uses exactly the same plug type as my GT.
I just replaced them as the car was starting to misfire and stalled once.
When I removed the plugs, (V6 and manifold off job) I found them to be the original factory fitted plugs.
These had been in there for 12 years and have covered almost 160K abusive miles.
They were royally f*ked, I've never seen a set of plugs so bad, yet they had only just started to exhibit faults.
Theses plugs are also buried deep in the engine under individual coil packs so essentially very much the same scenario as the AM engine.
So the point here is 12 years, 160K miles and every start will be a cold one in that motor.. lol
Plugs are not as delicate as we are led to believe by the main service agents.
As BR pointed out if there are no codes flagged then why change them?
Of course if the manifolds are coming off anyway for other work then yes take the opportunity, so long as you only pay £50 a set ;-)
michael gould said:
avinalarf said:
So next year my DB9V will need 7 year service say 17K miles should I change the plugs ?
NoI think a pragmatic approach would be to first remove air filters and see if they are wet with oil beyond the normal film. If the answer is yes, the breather circuit valves need changing and it makes economic sense to change plugs and breather circuit valves at same time. If the answer is no and the diag kit reveals only 'normal' misfire counts then it is acceptable to postpone.
The reason for such an approach is not just to eliminate spend on plugs when not required, but only perform an inlet manifold removal once. Also important here is that if plug change is delayed and breather circuit valves are ok, another consideration would be a potential coil failure, which is fairly common on V12. So, if plug change was delayed and perhaps in year 9 a coil fails (year 8 breather circuit was ok too), use that as a prompt for the time to replace all 12 plugs, 12 coils and the breather circuit valves. This means inlet manifold removal once in 9 years and they should not need to come off again for many years to come.
I often come across owners that have had inlet manifolds removed for plug change, then again for a coil fix, then later again for breather valve renewal, the end result is lots of labour duplication to reach the same end point - all parts renewed. So at around this age plan to remove inlet manifolds once and get the lot done same time, especially if car is a medium term keeper. This means happy days come paying for Service if stuff is postponed, but get ready for a spend in future to correct all.
BamfordMike said:
michael gould said:
avinalarf said:
So next year my DB9V will need 7 year service say 17K miles should I change the plugs ?
NoI think a pragmatic approach would be to first remove air filters and see if they are wet with oil beyond the normal film. If the answer is yes, the breather circuit valves need changing and it makes economic sense to change plugs and breather circuit valves at same time. If the answer is no and the diag kit reveals only 'normal' misfire counts then it is acceptable to postpone.
The reason for such an approach is not just to eliminate spend on plugs when not required, but only perform an inlet manifold removal once. Also important here is that if plug change is delayed and breather circuit valves are ok, another consideration would be a potential coil failure, which is fairly common on V12. So, if plug change was delayed and perhaps in year 9 a coil fails (year 8 breather circuit was ok too), use that as a prompt for the time to replace all 12 plugs, 12 coils and the breather circuit valves. This means inlet manifold removal once in 9 years and they should not need to come off again for many years to come.
I often come across owners that have had inlet manifolds removed for plug change, then again for a coil fix, then later again for breather valve renewal, the end result is lots of labour duplication to reach the same end point - all parts renewed. So at around this age plan to remove inlet manifolds once and get the lot done same time, especially if car is a medium term keeper. This means happy days come paying for Service if stuff is postponed, but get ready for a spend in future to correct all.
BamfordMike said:
That's a good point. The V8 is flat washer type so less chance of not coming out when asked, V12 is taper seat and that construction can sometimes be more prone / possible to get stuck in, but not seen a case of this before either, but sure it can happen.
Absolutely correct. The spark plugs will not "wear out" in this mileage or time with the Platinums or iridiums installed, but with cars not used regularly, there can be a corrosion build-up on the end threads of the plug, which when an attempt is made to remove it, can pull the thread out of the head on an aluminium head car.I have seen plugs so tight that a knuckle bar has been used to try and remove them at 60,000m and actually rounded-off the hexagon of the plug or shattered the porcelain with the force. We have then had to drift a torx bit down through the hole left by the shattered porcelain to use it as an ease-out to remove whats left. 9 times out of 10, the head needs removal to clean the debris fallen into the cylinder.
The car is always out of warranty by this point, although being maintained to manufacturers recommendations, and there have been some VERY heated exchanges between the garage technicians and the car owners as to who should pay for the subsequent repair.
Clearly, it is not the technicians problem that the splugs are seized in, but try telling a non-mechanically minded owner that.
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