Crankshaft Damper v12 6.0 LT

[Fiatson]

Anyone out there know where I can lay my hands on a crankshaft harmonic balancer for a 6.0 lt V12?
Alternator is polly-vee belt type drive.

Regards Fiatson

[poprivet]

Can't say I've ever heard of one of those need replacing before. What is wrong with it?
(Sorry I don't know where to get one!)
Pop

[Mark_B]

I had to do mine a few year back, sounds bl***y horrible rattling like big ends gone.

plenty of cars breaking on ebay at the moment a search will find

[Fiatson]

Just to explain what a crankshft damper is, it looks just like the pulley at the front of the crankshaft, in fact most will double up as pulleys.
The centre and outter are joined by a vulcanised rubber ring so they act as a unit albeit with a certain tiny amount of torsional movement.
It works in the same way as say a compressor mounted on rubber feet as opposed to it bolted to the floor, it isolates the resonance
They are fitted to most cars these days and many are dual harmonic having silicon compounds as well.
The pupose is to stop any harmonic resonances inherant in the engine from developing, these would vibrate and if allowed, would reduce the life of the engine and like the opera singer's glass possibly lead to cranshaft failure. Not to mention the irritation to the occupants.
It seems the 5.3 is inherantly a much smoother engine than the 6.0. So it is possibly easier on the damper?
However what I find is the most likey cause, is a coming together of several things.
The engine power (torsional load), the alternator (torsional drag), the driver (hard driving with all the electrics maxed out ie the heated seats, heated window, headlights all on) and possibly an overtightened alternator belt. With time it has to give.
It is interesting to see that Jaguar have changed the belt to a polyvee type wheras the previous types are single vee and possibly slipped under load when asked to knock out 120 amps?
If we lived in America then it would be possible to have the damper remanufactured by a company called Damper Doctor.
Here it is either second hand, not many late 6.0lts of any kind being broken at present. Anyway what chance the secondhand one would be much better or last particularly long.
Labour and time being the overriding concern here.
New, only Jaguar are temporarily out of stock! Could be the 12th of next month or the 12th of never.
The cheapest would be to fit a 5.3 but you'd have to change the alternator which is really no big hassle just adds to expense.
I suspect these 6.0 lt and that includes the odd Double Six and XJ are a damper problem in the post for most owners.
My car has done a 100k so it's not an unreasonable mileage. However I've only had it six months so ther was no way of knowing when the damper went, as the car drove and seemed fine.
I'am however agreat optimist and the car will be sorted in good time and at small expense (Coming from the north and being a ex-mechanic).
The secret with these cars is forget the keyhole surgery approach be masterful and organised with loads of boxes and keep nibbling away at the problem. When did you last eat your dinner in one mouthful?

The Fiatson

[Martin]

Hmm - this is interesting. I just posted something on another thread about engine smoothness. Try this link for information

http://www.e31.net/engines_e.html

As I understand it the V12 is inherently smooth. If that is so why does it need dampers? Or am I being too simplistic?

[Fiatson]

In reply to the question why does a v12 need a damper, having given it thought I have several possibilities gleamed from my days in the trade as a bus mechanic.
Even with twelve cylinders, a piston engine is still not as smooth as a turbine engine because the power comes in pulses. There is certainly a need to smooth the pulses out else why the need for a flywheel?
These pulses are harmonic like music they have time duration and also magnitude. Based on engine speed and throttle position.
Ever driven an old diesel car, sat in traffic at the lights listening to the dash board rattle? Why does it do it? It has no power source?
It vibrates in sympathy to the engine's vibrations.
To stop it you change the frequency by changing the tickover. Or you could isolate it by packing with rubber mounts I prefer the first.
The crankshaft damper works in the same way as rubber feet on a motor it isolates the frequency stopping harmonic resonance within the engine causing other parts to vibrate in sypathy.
If anyone can enlighten me further please do so. I was always told by an old boy mechanic (oilly hair, road map hands and with half a finger missing) to always listen to what anyone has to say, then keep what's useful and disregard the rest.

My next little entry regards how I've fixed the problem. I did in the end opt for the genuine part but this is where you need to be pally with the storeman and not sit in the comfy leather seats drinking proper coffee.
I suspect your local Jaguar garage is like mine extremly pleasant but has no door saying stores or has a sign saying workshop customers keep out...for health and safety reasons whatever they might be.
You are not supposed to go into the inner sanctum because your place is on the leather sofa.
I walked into the stores after politely asking the power suited lady in reception where they were.
To cut a long story short I asked for the price and availability of a new damper. First knock back £241 plus vat.... second not available at present However you shouldn't be put off. After looking at alternatives it turns out that the part is a superceded one. Is the earlier part available,yes how much £85 always keep pleasant and ask for discount 10 % you get it with the club but even if you don't, then ask for the item to be placed on a stock order. It takes longer than VOR (vehicle off the road ) but the discount to the garage is usually bigger and the storeman if nice will pass a little onto you.
Everyone does things differently but if you can get a storeman who is interested in his job, likes to help and relishes a challenge you will have a great ally in the war to keep the cat purring.
Front crankshaft oil seal normally£40 plus vat. First attempt at the local bearing shop met with no success Jaguar only I thought about it then called again. The V12 has a lot of imperial sizes in bolts etc. It was after all built in the swinging seventies where the question have you metric was answered with no...but I've met Dave So I called again and an old boy answered the phone this time not achne Andy Boy racer with the pedal bin exhaust and the 1.1 popular badge removed in favour of the badge "if you can read this you're probably passing me."
Straight away he converted the measurement 0.5x2.125x 2.785 " to HALF AN INCH by INCH AND AN EIGTH by TWO AND SEVEN EIGTHS.
Got one on the shelf lad £2.50.
Oh as for the spacer that Jaguar would have you buy, turn the one on your car around just like new.

Hope I've saved someone else from wasting valuable petrol money. Never accept the first thing your told without a second or even third opinion. Fools and money are easily parted as my old dad says!
If it costs money theres's always a cheaper way

The Fiatson

[Mark_B]

Well done solving the rare parts problem by taking an engineering approach. Generic oil seals and bearings I favour buying from rswww.com now rather than bearing stockists.

Interesting (well I think so anyway) subject about vibration isolation, it's not ordinary rubber in vibration isolators it's natural rubber, and the vibration loading is applied in shear mode (as opposed to in compression) because natural rubber has the best damping effect (energy converted to heat), the dunlop rubber used in the engine mounts, the rear subframe mounts, front subframe mounts (trailing ones), all used in shear mode even the original steering rack mounts are of natural rubber and yes again in shear mode, that's why when replacing with hard plastic bushes there's an increase in conducted noise. In a crankshaft damper is shear mode again, though isn't the reason for a CD is to prevent destructive harmonic vibration in the actual crankshaft itself, rather than for comfort?