Okay folks, what do you make of this ? Accessory belt is jumping a bit. Only happens on the first cold start of the day. Then it settles down and is perfect thereafter.


The tensioner and the idler pulleys have been replaced, and the belt is new. All Jaguar OEM parts. In fact the tensioner was renewed again, in case the new one was the problem.


Before this, the car threw the belt once. One of the pulleys was noisy, hence the need to replace the tensioner, idler and belt in the first place.


Alternator is about 2 years old, the power-steering pump is about a year old. Aircon was switched off, and is the original unit. Water pump pulley seems fine, history is unknown, could well be the original. Crank pulley looks okay to the eye and is original.


All pulleys and bearings feel okay to the touch, so nothing obvious amiss really.


Car is a 4.0 XK8 with 92,000 miles





[youtube]isBMXplWhwE[/youtube]

 

I have 2 videos on my page with the same problem I ended up replacing the idler, tensioner and belt.

Link JagRepair.com - Jaguar Repair Information Resource

 

Someone will know better than me, but it seems that the pulley on the alternator should only be just as wide as the belt. It seems too wide here. Not saying that is the problem, it just doesn't seem correct to me. Then again, I never looked.

 

I expanded Gus's pic and see the alt has a (correct term) ridged pully as does the belt, it the alt that was replaced wasn't oem first check to ensure it has these which it probably does, hence the blet mistracks as Gus says and pulls the tensioner when it rides of these.

 

Might be worth checking that you have the correct belt - there seems to have been a change at vin:042775

 

@franksm - I have just had the exact same problem with my car. I replaced the tensioner, the idler pulley and the belt and so far the problem is gone. All bearings and pulleys felt OK when manually spun - just as you mentioned.

 

My 98 is suffering from the same issue. All pullys/tensioners and the harmonic balancer have been changed. Yes, it is the correct belt, too. Any other ideas???

Scott

 

Hi Scott....did you solve the problem? I have the same issue with my car, I suspect the bearing in the alternator;-(

 

Yes/No. It was okay for a while. Even after the original repair work, it still had a slight belt squeal on startup but it would quickly go away.but upon first startup this spring, it threw the belt within 15 seconds. When I was putting the belt back on and had a socket/breaker bar on the tensioner, it seemed exceptionally stiff with very little flex. After reinstalling the belt, no squeak, no noise. Within a week, the startup belt noise returned, I only drive it about 5,000 miles a year but the serpentine belt is showing wear and I think the mechanic used an aftermarket tensioner which from the feel of it when moving it, I just don't think is working correctly. So, I'm going to order an OEM tensioner and belt and try again.

On the bright side though, over the winter I added extra ground wires from the tail light ground planes to the chassis and that fixed the " rear bulb failure" message.

 

Forgot to post a reply on the new belt and tensioner.

IXLLER8, I ordered and installed an oem belt and tensioner. Tensioner p/n wasNCA7739AE , belt p/n was NCA2211AC. This seemed to resolve the issue. The previous tensioner installed by the repair shop was an aftermarket part and I don't remember for sure if the previous belt was oem or aftermarket. I did notice that when I removed the old belt by taking the tension off of the old tensioner and then when installing the new belt on the new tensioner, it took a lot more effort to move the new tensioner. The old one had about 9,000 miles on it. I wonder what the difference in the amount of pressure is between the two. Maybe the old one was allowing the belt to slip a bit or it just wasn't flexing correctly???

 

I have the exact problem except that I have a no charge issue. Put a straight edge across the Alt pulley and it isn't paralle with the Idler.

 

Is this a new problem or has the offset been there all along? Do the rest of the pullys line up or is it just the idler that is out of alignment. Has the alternator shifted in its mounts somehow?