Serpentine Belt
#1
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Just put a new belt on our 2005 XK8 and it is thumping like crazy. Looks like it wants to jump off running back and forth on idlers making the tensior pulsate. It's a Gates belt but understand Dayco made the original.
Have any of you had this problem? If so, which belt did you end up using?
Jack
.
Have any of you had this problem? If so, which belt did you end up using?
Jack
.
#2
Join Date: Jan 2018
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Y2KJag (03-25-2024)
#3
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Just put a new belt on our 2005 XK8 and it is thumping like crazy. Looks like it wants to jump off running back and forth on idlers making the tensior pulsate. It's a Gates belt but understand Dayco made the original.
Have any of you had this problem? If so, which belt did you end up using?
Jack
.
Have any of you had this problem? If so, which belt did you end up using?
Jack
.
It could also be a driven component failing just as you installed the belt but that would be an unlikely coincidence.
Richard
#4
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I checked the idlers, and belt length was checked at parts place. I marked the tensioner arm before removing the old belt then again with new, it hardly changed at all.
I only changed old belt while I had access because the old belt is 21 yrs old. The car only has 34,000 mile on it.
I did read somewhere else that another person had exactly the same problem with The gates belt.
I will check it all out again as I remove it next week.
Thanks for the help.
Thanks
Jack
I only changed old belt while I had access because the old belt is 21 yrs old. The car only has 34,000 mile on it.
I did read somewhere else that another person had exactly the same problem with The gates belt.
I will check it all out again as I remove it next week.
Thanks for the help.
Thanks
Jack
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RichardS (03-23-2024)
#5
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cjd777 (03-23-2024)
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#8
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my car is a 2002
your belt has six ribs. The gates belt on my 2002 has seven ribs and the part number is K070922
So according to RockAuto (infallible??) the 4.2 cars use a different belt
your belt has six ribs. The gates belt on my 2002 has seven ribs and the part number is K070922
So according to RockAuto (infallible??) the 4.2 cars use a different belt
Last edited by zray; 03-24-2024 at 07:49 AM.
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#11
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#12
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Our 1997 4.0 XK8 is 7 rib whereas our 2006 4.2 XK is 6 rib as I've changed both at one time or another. I don't know whether this helps the OP but it would be impossible to remove one type of belt and replace it with the other as the difference between them is so obvious that you would spot immediately that something was wrong.
Richard
Richard
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zray (03-24-2024)
#13
#14
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No progress on belt. When first started cold the belt looks like it's trying to jump off the alternator pulley. looks like the belt has a knot on it going across the pulley but it doesn't. The pulley is running true . After about 30 seconds the belt runs great and doen't act up again until after cooling off all day when it will do it all over again.The routing is correct also.
I do however think it is a defective belt. Never a problem until I installed the new belt.
Jack
I do however think it is a defective belt. Never a problem until I installed the new belt.
Jack
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RichardS (03-26-2024)
#17
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No progress on belt. When first started cold the belt looks like it's trying to jump off the alternator pulley. looks like the belt has a knot on it going across the pulley but it doesn't. The pulley is running true . After about 30 seconds the belt runs great and doen't act up again until after cooling off all day when it will do it all over again.The routing is correct also.
I do however think it is a defective belt. Never a problem until I installed the new belt.
Jack
I do however think it is a defective belt. Never a problem until I installed the new belt.
Jack
Is it only the alternator pulley which seems to affect the belt? If so, that could be because the alternator is a small pulley with a larger percentage of wrap-around and the alternator usually imposes a higher load on the belt when the engine is cold so any problem with the belt internal structure will probably show up on that pulley.
The other alternative is that there is a problem with the alternator but I would expect to hear noise from the cold alternator and you could test it by removing the belt and spinning the alternator pulley by hand to check for resistance. Replacing the original belt, if you have kept it, would be worthwhile.
Richard
#18
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I do still have the old belt and plan to re install it for comparison probably next week. I've never seen anything like it.
I have a 1989 ford F150 that had a very old and frayed belt so decided to change it. The first new belt lasted maybe 20 miles and the second new one lasted but a little longer. after a good look I found the tensioner swing arm tilted about 2 deg leaning the pully back toward the engine.
I went to the local scrap yard and found 2 others made the same way and one that was straight. I got the straight one and it's been fine ever sense. The previous owner had apparently installed the wrong tensioner. The old limber belt ran fine while the stiffer new belt revealed there was a problem. I can only see movement at alternator pulley and only for 30 to 40 seconds then it is fine. My son cranked the car while on lift so I could observe it. There could be a stiff place in the belt as someone suggested that limbers after several revolutions. I'll look for problem at alternator first.
The new belt in this situation may be telling something isn't right. The idlers felt like new, roll smooth and no loose bearings.
I just dread draining the coolant and removing the hoses. I have very large hands and arms and there is no other way that I know to get it off.
Hope I only have to do it one more time.
Jack
I have a 1989 ford F150 that had a very old and frayed belt so decided to change it. The first new belt lasted maybe 20 miles and the second new one lasted but a little longer. after a good look I found the tensioner swing arm tilted about 2 deg leaning the pully back toward the engine.
I went to the local scrap yard and found 2 others made the same way and one that was straight. I got the straight one and it's been fine ever sense. The previous owner had apparently installed the wrong tensioner. The old limber belt ran fine while the stiffer new belt revealed there was a problem. I can only see movement at alternator pulley and only for 30 to 40 seconds then it is fine. My son cranked the car while on lift so I could observe it. There could be a stiff place in the belt as someone suggested that limbers after several revolutions. I'll look for problem at alternator first.
The new belt in this situation may be telling something isn't right. The idlers felt like new, roll smooth and no loose bearings.
I just dread draining the coolant and removing the hoses. I have very large hands and arms and there is no other way that I know to get it off.
Hope I only have to do it one more time.
Jack
Last edited by JACKP; 03-26-2024 at 06:46 AM.
#20