Hello everyone. I'm new to jaguars. I bought myself a 1998 Xj8 and I'm really happy with it. I'm finally having some trouble with it. I purchased her this summer. My serpentine belt tore a bit along the edges and came off. I then just replaced it thinking it was just old or something. Turned the car on and it ran perfectly for about a day. Then on my way to work it slipped off again. It didn't break or tear, it just slipped off. Put it into the garage and started to diagnose the problem. Rerouted the belt again, started the car and it slipped off again (right by the idler) and the new belt tore just like the old one. Figured it was a bad tensioner because the belt wasn't as tight as i though it should be. I bought that, and i also went ahead and bought a new idler pulley because that is where it kept slipping off. Once i had all my new parts we rerouted the new belt. I turned the engine just by flicking the key a little so it wouldn't fully start because i didn't want to risk breaking another belt. My pops was watching the belt while i was turning the key and he could tell the belt started to slip in the same place, right by the idler pulley. Stopped to make sure everything was routed correctly, which it was. We were also able to move the belt back into position by hand as if the belt wasn't tight enough. We are sure it is the correct belt. The tensioner and the pulleys are also the proper parts, so I'm ruling that out. We stopped there so we could do some more research on how to try to fix the problem. Could I please get some information for someone if they've had this same problem in the past?

 

Check for misrouted belt and make sure the mounts for all pullys are not bent or broken. Did you change the whole tensioner, or just the pulley part? Is it mounted right? How do you know the belt and pulleys are "right"? The key is that you say the belt slips back on easily, so either the parts or path is wrong or the tensioner spring is not working.

BTW, I seem to recall an alternate belt path would almost seem right.

 

None of the pulleys wiggle and they all seem to be in line and parallel with the engine block. After routing the belt in the correct pattern (we triple checked this) it bounces just by pushing on it. There is tension on it but it doesnt seem like enough. None of the other pulleys move or wiggle when you push on the belt. It seems like it has to be a tension problem. I did replace the tensioner with a brand new one though. It is the correct one for sure checked the serial numbers on the part as well as took measurements on the unit. What do you mean when you mentioned an alternate belt path?

 

I meant I had the belt on wrong, but thought it was right!
I don't want to come off as a wiseass, BUT, if the belt is right, the pulleys are right, the tensoner is mounted right and is good, the belt is impossible to slip on without releasing the tensioner tension with a long wrench! Have look at the picture and be SURE! If you have that right, then I would say you need to examine the tensioner to see if it is not broken. or installed incorrectly.
BTW, the belt length is shown by vendors to be between 91.54 and 92.32 inches long. Don't know which is "correct".

 

If you have the correct belt putting it on would not be as easy as slipping it over the tensioner. You would have to exert a good amount of pressure on the tensioner with a big spanner to retract it back far enough. Even then you would be cursing as the belt is a tight-ish fit. When the tensioner is released it should pull the belt tight and no way should it slide off. If you are not cursing and swearing when you put it on, something is not right. I would suggest the belt is too long and you might need the next size down. Either that or your tensioner isn't working, is the spring very strong or very weak. It should be very strong.

 

Does the picture you attached show the correct path for a 98 XJ8? Many thanks in advance!

 

Looks about right. Just did my 2000, same engine (non supercharged). You should also be able to check per the belt and pulleys. Rib side to grooves, smooth side to smooth pulleys.
Confirming what they said. With maximum oomph on tension pulley, belt still barely slips on. Under tension, no slip, no way.

Good luck

 

Be careful with the tensioner; they get fragile . .

 

Just to pile on, it does take some good cursing and prying to get the belt on. If all else is correct, maybe there is more than one length of belt and you need a shorter one.

 

Thank you! We have determined that the tensioner is fine. I have a strange "rattle" that can really only be heard inside the car. It's not loud per say, but if you don't have the radio or AC,my out can hear it. We have had it on a rack at listened with a stethoscope to everything underneath and under the hood but can not locate it! I know this is generic, but any ideas....anyone?

 

Did you have a plastic pulley on your old tensioner and a steel pulley on your new tensioner? The reason I ask is there was a change in the pulley from plastic to metal between 99 and 2000 I believe, even though the part number remained the same from what i remember. You can only buy the upgraded metal pulley new now, and it requires a different belt part number (92.32") and a swap to other upraded pulleys. It will not work just upgrading to just the metal pulley and running either belt size from my experience. Either find a used plastic tensioner on ebay and run the old 91.54" belt or use new tensioner, change the other pulleys needed (sorry cant remember what is required specifically), and run larger 92.32" belt. Hope it helps point you in the right direction. Sorry for being redundant!

 

3timejag:
Your statement makes many of us cringe! You have checked your secondary tensioners to be SURE they are upgraded, right? If not, before you crank the engine again, check the archives concerning bad secondary tensioners and what happens if one breaks.

You have been warned!

 

Yes, the tensioners are the upgraded metal body style, and there is no noise from left or right areas, thanks! The noise is strange, in that when you are sitting in the car, idling, it sounds like it's coming from almost behind the radio to gear shift area. It very slight but enough to be annoying. It also seems to have started after the serpentine belt slipped off and then was placed back on.

 

Run your stethoscope along the right and left fuel rails; sometimes the injectors will click more loudly if they are dirty.

Turn off the a/c and heating system, sometimes the fans will be shuddering a piece of sound deadener in the airways.

Put the stethoscope alongside the throttle body.

Along the back of each exhaust manifold: blocked mufflers will make a throaty (howzdat for techy talk?) rumble . . .

Water pump; power steering pump . . .

 

Thank you SO much! We did hear clicking in one bank of the fuel rails. Is there any procedure that you know of to clean the injectors? If so, how would I know if I had the option to clean or need to replace?
Wow, that makes so much sense now that I think about the noise I am hearing as the "needy" side fuel rail is the one closest to the driver seat.

 

That was the noise?

pssst, don't tell Ross: maybe a can of SeaFoam?

Actually, just drive the car: overtime they will clean up at speed. Try switching gas to Chevron (BMW's choice) or something with a little more cleaner.

 

In case you have no Chevron stations in your area (like me), Chevron also sells their polyetheramine fuel cleaning detergent separately (Chevron Techron Fuel System Cleaner).

 

Many thanks to All for the suggestions! Chevron gas w/ additive it is.....will let you know results in a tank or so!

 

Gogurt92: has your belt issue been resolved? I had a belt issue last winter on my '01. The colder the morning (speaking Austin, TX here, so not THAT cold), the louder 'clack/clack' noise was coming from [what I eventually diagnosed to be] the tensioner. Didn't pay too much attention as went away relatively quickly at engine warm up: BUT the belt eventually got ripped apart ! I installed a new belt (all the cursing referred to in the thread is CORRECT) and been working just fine since. Winter is approaching again and suspicious if I'm going to have same symptoms again... did my pulley cause the belt to tare or did a bad belt had the pulley go a little nuts... I have on my to-do list to eventually replace my tensioner pulley.

 

Jhartz, Jim, just for info and to double check, what would I be listening for when placing the scope on the throttle body housing? Thank you sir!