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02 xk8 belt walks off idler pulley have replaced idler tensioner and crank pulleys and bearings all look good new belt won’t stay on wobbles at alt and idler new idler from jag does not have lip like old one any ideas
A year or 2 ago Anthony posted about the raised edge idler issue on his 1998. As I recall he found 1 . Look at archives . I suspect bigger issue here though.
All was good belt came off in pieces replaced Belt month later belt off again sent out to get checked out replaced tensioner and idler pulley from jag belt came off mechanic said only thing they could see was slight wobble of crank pulley replaced it belt still walks off idler new idler does not have lip on outside like old one wobble looks like it starts by alt and idler long run
Brainstorming: no belt tension - are all the pulley's bearings tight? If you turn by hand do they have play/wobble? Your crankshaft pulley is solid right?
New tensioner with good tension no play or wobble in any pulleys alignment looks good replaced crank pulley and idler new idler from jag does not have outside lip like old one
Later & replacement idler pulley lost its lip:- I guess Jaguar decided it was superfluous due to its proximity to the alternator.
I replaced both idler & tensioner pulleys with Dayco 89016 as the bearings were grumbling at 30K; subsequent paint wear on the idler shows there's a small amount of 'wandering' along the stretch from the tensioner, but no problems.
Only thing I can think of that will cause the belt to throw is a pulley misalignment somewhere - as per Bob's link, or a stiff bearing?
I have attached the diagram of the belt tracking path. If you are having a wobble at the alternator to the idler the belt is trying to get back on track. My engine has a smooth pulley on both the Idler and the Tensioner. neither one of them determines tracking they both ride on the smooth side of the belt. You stated that the crankshaft dampener has been replaced. Your most likely cause of the problem is that it wasn't replaced correctly. The belt travels from the crankshaft to the alternator over the tensioner and idler. The tensioner because of spring pressure won't vibrate but the idler will as the alternator tries to correct the path. If the crankshaft dampener is out of line it will feed the belt incorrectly to the alternator leaving the alternator to try correcting it as it rotates on around. Check the alternator pulley for signs of rubbing in areas where it shouldn't be touching.
I would get the bolt removed from the dampener and check the dampener seating.
I had this problem about a year ago on my '97 XK8. Here is what I wrote (and how I solved the problem):
The belt was slipping off of the smooth idler pulley (on the passenger side of the motor). I put a shim (thick washer) behind the pulley and it worked a treat. Don't know if I lost the original shim during the project, but one problem solved.
Belt walks off
