I have a 98' XK8 which is all stock.. The previous owner has done some work on the front of the engine, replacing the timing chain tensioners. He is a professional mechanic from the UK and specializes in British cars. That being said, the serpentine belt stays on the engine for about two months before it flies off again. I suspect that there is a miss-alignment of the pulleys and tensioners going on, but that is only a guess. The serpentine belt was new four months ago and it come off twice since being replaced. I am getting tired of my business partner laughing at me for driving a British car as he gets in his Japanese and drives away and I am enjoying putting the serpentine belt back on in the rain.
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So, does this sound like miss-aligned pulleys? Or could there be something else going on?

How do you determine if the pulleys are miss-aligned?

Thankss for thoughts and recommendations.

 

Nevada, I don't have the answer, but wanted to check on 1 thing. Are you saying you can reuse the "Undamaged" original belt each time? Have you ever changed the belt to a new one?

John

 

 

John, yep, it came off and I simply put it back on. I checked for damage and saw none.

 

David, I will check all of the pulleys when I get it home. The car decided to do this when it is raining here in Las Vegas - it is all about the timing.
How do you adjust the tension on the spring tensioner, I thought they were all pre-set

 

Just remembered a post from way back. Is your idler pulley making noises? A common problem with our cars, the bearings in this pulley go bad. One member, Dave, had his belt jump off due to this issue once.

Probably a long shot, but it did happen once. When my pulley went bad, I confirmed it by relieving pressure on the serpentine belt, turned the pulley by hand - it was anything by smooth. Felt like a stepped or notched bearing support.

FWIW, before I changed it, it make quite a noisy racket at low speeds or idle.

John

 

This has come up before. From memory, there is an idler pulley with a "lip" and another one without. Maybe the prior owner replaced the idler/tensioner with a part that happens to be incorrect for your engine. Check this with a reputable catalog, like the excellent SNG Barratt.

As usual, you might want to check all the accessories with the belt off. Spin all of them by hand, check for rough spots, or anything loose. Also check for leaks/contamination from the water pump or power steering. If the prior owner did remove the front plate, double check the tightness of the crankshaft bolt. It takes an insane amount of torque to be set right. In the off chance it has worked itself loose (unlikely).

Best of luck, keep us posted.

 

I have ordered a new serpentine belt. I will check the idler pulley, both for running and type. While the belt is off I will address the chrankshaft pulley as well and see if it is lose at all. Will take a good look at all the accessories to make sure they are running correctly.

Thanks guys.

 

 

I had a low volume squeaking noise from the front-right on startup, that lasted about 5-10 seconds, and expected that an alternator bearing was on the way out. While waiting for delivery of the alternator, the belt threw itself off while driving, fortunately about 1/2 mile from an auto parts store. One quick look with iPhone light showed the idler pulley was gone. Only the nub if the inner race and the bolt holding it on remained. It was my good fortune that the parts were on the shelf at Autozone (one of the benefits of sharing many parts with Ford/Loncoln fron the same era), so one idler pulley/bearing assembly, one belt, one 15mm box-end wrench, and I was mended in about 15 minutes.

So be sure to check both the tensioner and idler pulleys, no need to put a new belt on with a faulty bearing.

All the best,

Jerry Lippmann
1999 XK8 BRG 124Kmi

 

I had a problem where the belt started being chewed up and I realised that there was something wrong with the idler - it looked perfect, didn't seem to have any play in it, but the belt kept 'wandering' offline and getting damaged. Luckily when it first happened it chewed the first couple of ridges off the belt, but the rest was still intact, allowing me to experiment without damaging a new belt. I changed the idler and the problem went away, despite there being no obvious difference between the faulty one and the working one.

 

After doing a chain tensioner job on my '97 XK8, I had a problem with the belt popping off (possibly unrelated to the other work). To fix it, I shimmed the idler pulley, which doesn't have a lip, with a thick washer. In retrospect, I probably would have done a little better by replacing the idler pulley, as it is inexpensive (and I think my fix squeaks a bit). However, I have about 3,000 miles on the car after my fix.

 

The weekend was productive I'm thinking. I buckled down and cleaned up the front of the engine, it has had an oil leak coming from the front crankshaft oil seal throwing oil all over the serpentine belt and front cover. The belt tensioner was replaced a short time ago by the previous owner, I am not sure about the idler pulley, but I see that that will be happening in the next week or two, per bladerunner919 and TruckGraphics posts. How much could the oil on the serpentine belt impact the belt coming off, especially the idler pulley that has no edges on it.

 

 

I have heard it is a task to fear....
I cleaned the engine to the point there were no traces of oil on the rag using engine cleaner. Wiped it down with water. Added florescent dye to the oil and ran around the neighborhood for 10-15 minutes. Put the car up, got the black light out and there was glowing oil that ran below the center of the damper on the timing cover. The edges of the damper were glowing all around. Glowing oil spatter tossed in light volume, on other parts of the belt/pulleys. From this I surmised (always sounds better than "assumed"), that the oil leak was from in back of the damper, hence the crankshaft front oil seal. But this is the first time I've tried this glowing oil approach. I am more than open to different interpretations, learning here.

 

It does sound like the crank front oil seal.

The good news is that it can be replaced without removing the timing cover - er - once you have the damper off. Seal should have been renewed if the primaries have been replaced but maybe didn't locate properly? There's a note further down the thread that it can be pushed in too far.

The procedure is shown in JTIS 12.21.14. Member Mish_Mish has some pictures (note his is S/C):
https://www.jaguarforums.com/forum/x...98/#post710748

I'd still check both the pulleys 'while you're in there'. They are not expensive and do seem to have a shorter life than the belt.

 

The first thing to check is that the belt is routed correctly. If it driving something backwards, it will pop off every time.

 

Some of our cars have an oil cooler. The oil lines come in/out of the engine in that general area below the crank pulley. It seems like you have already a clear picture of where the leak is from, but double check these rubber/Aluminum sections. They do not age well, and leaks are common. The point is that is way easier to fix than anything related to the crank seals, just to rule it out.

Best of luck, thanks for sharing the dye technique.