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When I put my car in for a physical at JEF, the guy there let me know he'd actually not finished after he'd told me he'd finished and I'd booked trains and hotels and paid the bill. He said he tracked down the whine the engine makes on starting when cold (especially in the cold) to the "crank pulley damper rubber slipping. This happens when the battery charge is low* and the alternator has to work harder." It doesn't seem to affect how the car drives (yet), but I would of course prefer not have my cat howl likes it's in heat when I leave home.
*Does this mean a new battery is a good idea? Mine seems fine (still shows green on top, not red). Or perhaps a more powerful battery?
As he hadn't actually fixed it before I picked up the car, I need to arrange that myself. I believe the part is No. 14 in this diagram. Part Number EAC9693. I've found one on EBay for US$249, though shipping is over $100, which is painful. I'll keep looking, but before I buy something so expensive, it would be nice to know that it's the right part. And won't be too heinously ruinous to replace....
Often worse right after start-up and/or if the battery is discharged, yes, due to alternator load as mentioned. A new battery, even if needed, won't solve the actual problem.
Here in the 'States there are companies specializing in dampener re-bonding which would save you quite a bit of money....if shipping doesn't gobble-up the savings
Thanks for your usual great advice, Grant and Doug. I wonder if there are companies in Japan that can rebond dampers. Might pay to ask my usual garage.
Interestingly, doing some more poking around suggests that one sign of a problem is engine vibrations. Would be nice if replacing the damper also made the engine pass the coin test....
One final question before I order, if you don't mind. There seems to be a huge range of prices. The cheapest I've seen in US$199 (eBay), while the most expensive are around $600 (Jagbits and Coventry West) or even more. Is this sort of difference usual, or is the eBay one likely to be Chinese junk that will fall apart in three months?
It's an expensive part, so I don't want to spend more than I have to--but I don't want to end up spending double by using inferior crap.
I wonder what could happen if you left it as it is?
That's the thousand-dollar question, isn't it? Apart from a whine for a few minutes when the engine's cold, what actually is going on? Would using that spray stuff people use to stop belts whining be a quick and easy (if temporary) fix?
If it would also fix the slight vibrations at idle, however, it would be worth it (though I have to admit, the car's so quiet that those vibrations are sometimes the only reason I know it hasn't stalled! More than once I've had to check the tach to make sure that yes, the engine is still ticking over...).
Well the picture of that $200 one is for a ribbed belt, so you would definitely need to ask if thats a generic image or not.
My thought is you don't want this slipping to the point the whole thing is just free spinning, right? Isn't the best temporary bandaid to turn up the idle?
The image seems, as far as I can tell, identical to every other image of the part I've seen. Here's one from XKs Unlimited, for example. Motorcars Ltd. have several images, and they're all for ribbed belts.
If the whine/squeal no longer goes away after a few minutes, I might try turning up the idle, but when it gets to that, it's definitely time to replace....
Leaving it as is will lead eventually to no drive at all for the alternator but because that pulley is captive between the marelli timing fingers and the bolt on pulleys at the front of damper no collateral damage will result from total failure.
The dampers are interchangeble between the 5.3 and 6.0 litre marelli motors other than one needing the seperate locking cone and one not. I run the damper from my 5.3 marelli on my 6.0 litre.
l rebuilt my own damper using a jig and heat cured polyurathane some years ago, still going strong.
That's the thousand-dollar question, isn't it? Apart from a whine for a few minutes when the engine's cold, what actually is going on? Would using that spray stuff people use to stop belts whining be a quick and easy (if temporary) fix?
If it would also fix the slight vibrations at idle, however, it would be worth it (though I have to admit, the car's so quiet that those vibrations are sometimes the only reason I know it hasn't stalled! More than once I've had to check the tach to make sure that yes, the engine is still ticking over...).
Hi Someday
When I first got my Grey XJS one of the Belts used to Scream like Crazy which made her sound like one of those Cars in 'The Fast and the Furious'
Which sort of gave the impression that you were going round Corners at an Insane Speed, even though I was only doing less than 20 mph
But when I adjusted the Tension on that belt it disappeared completely
When I come to think of it the thing that was making the Noise
Was the Pulley on the Aircon Motor and even now I still give that pulley a couple of drops of Oil between the Pulley and the Shaft before I go out
Who knows you might have exactly the same problem, that a couple of drops of Oil might fix
But if you do the Crank Shaft Pulley, then you may as well change ALL the belts as well while you are about it
So perhaps better to change it before the alternator stops getting power, perhaps. Even if there is no collateral damage, I'd prefer to fix it before total failure.
Couple of drops of oil might help, too. She does sound like she's revving up like a race car when starting off. Luckily it's only once per day, though worse on cold days. Actually, it's getting warmer here, so if I keep hearing this year, which I didn't last year, that's a sign it's definitely getting worse.
Grant
Is it the same part for Lucas ignition 5.3 engines, please?
Greg
Originally no, but the Lucas part supersedes to the Marelli part. There is a 3 pointed timing pickup on the Marelli damper than isn't needed for Lucas.
The damper is 2 pieces of metal bonded together with rubber, the center portion, and an outer pulley portion. The outer pulley portion is what drives the alternator belt.
Some theory first:
What should happen is the rubber is not 100% stiff, it can absorb a certain amount of torsion. The crankshaft does not rotate at a constant angular velocity, it is always speeding up and slowing down with the firing stroke of the pistons, and the force from each piston is not exactly equal. Close, but not exact. This creates vibrations. The outer ring of metal can kind of semi free wheel, but is constrained by the rubber.
Since the rubber flexes, the outer ring can run closer to a constant angular velocity relative to the crank, and this acts to dampen any torsional vibrations in the crankshaft. It takes energy to move mass, so the speeding up and slowing down of the crank goes into the rubber-ring assembly instead of vibrating the crank.
In Jaguar's case, they used this outer ring as a pulley, which is bad from an Engineering perspective for 2 reasons: The dampening effect is reduced as the outer ring is constrained by the belt, and the drive forces to turn the alternator are transmitted through the rubber in shear. Rubber is particularly bad at resisting forces in shear, and eventually either the rubber fails (rarely) or the bond between the rubber and the steel fails (very common). They did the exact same thing in the steering rack bushes - and they regularly fail.
Your squeal:
It is most likely due to the rubber-steel bond failing, and the outer pulley ring is slipping on the rubber, instead of being turned by the rubber.
There is an easy way to check for this. Park the car half on a curb or over a gutter or somewhere you can reach under the car to the front pulley. Jack it up if you have a jack. Then take a piece of chalk or a paint marker that gives contrast ( I usually use white) and mark a line across the 3 groove pulley ( this is bolted to the centre and the crankshaft) and the outer ring where the alternator belt is. make sure your mark lines up.
Then start the car. Drive it for a bit and then later observe your marks. If they are still lined up, there is no slippage in the damper; it's probably a loose belt. If the lines are no longer lined up, then you know the inner and outer rings of the damper have become debonded and it needs to be replaced/rebuilt.
Labour for a shop to do it shouldn't be that bad. The most time consuming part when I did it was the fine thread bolts on the belt adjusters. Not difficult, just time consuming to loosen and retighten.
Last edited by Jagboi64; Mar 28, 2018 at 09:27 PM.
Reason: typos
Thanks, Jagboi, for that very detailed description. Very helpful in understanding just what's going on. I'll nick some chalk the next time I'm up at the university, and mark a line like you say.
This, I gather, is the setup:
And definitely no oil anywhere near it in that case....
I'm 98% sure you have that labelled correctly. I have an old one in the garage that has debonded, let me look at maybe take a few photos. The only thing I am not 100% sure of is if the piece you labelled as the inner ring is actually the inner at that point.
Cold Engine Whine: Crank Pulley Damper Rubber Issue
