My serpentine belt popped off in a parking garage yesterday. The belt is in good shape. I had the car towed back to my house, and I put the belt back on this morning. However, as soon as I started the car back up, it popped off again, and this pictured pulley (dampener?) was rattling around. The bolt is loose. I believe this is the crankshaft damper?

Not really sure how this happened--my only guess is that when my power steering pump bound last week (which prevented the belt from moving) that the bolt somehow unscrewed itself.

Is this something I should try to DIY mend, or should I just send the car to a pro? If this is what I think it is, the process looks beyond my capabilities, and the torque specs (364-386 nm) are far beyond what my tools are capable of. And I don't think this is something I can just tighten back up anyway.

 

I should have done a forum search first. I found the TSB for this (303-05). Apparently this is a known issue on 1997 models. The bolt is a one use item because of the high torque and should not be reused or re-tightened.

Off to my mechanic it goes...

 

Crank pulleys usually have 2 parts: inner, outer and thin layer of rubber between. The rubber dries out and outer ring starts moving around inner.
If your bolt got lose and this is reason of your belt popping (not likely), I would remove bolt and used blue tread locker (2 drops?). Spec torque is very high, you'll need to hold crank somehow.(usually pry bar holding flywheel)
Check all pulleys/alt/w.pump for seizing/free play/rattling.

 

Ouch, it happened to me once. I remember my mechanic looked into it. There are 2 different replacements, each at very different prices. My luck I have the expensive one. I wound up buying a replacement from a donor car. I hope you are lucky and it's the lower price replacement.

FWIW the deciding factor is the serial # as I recall.

John

 

My '97 did the same thing this week (popped off the accessory belt because the harmonic balancer loosened).

And the same thing happened to me when I first got the car running several years ago. That time, I replaced the harmonic balancer with another that I bought from a junkyard, and also replaced the bolt with a new item. Surprisingly, the local Jaguar dealer stocks these ! (hmmmm ?)

I'm not going to buy a new balancer...at least just yet. Frankly, I'm a little peeved as I was really careful about re-installing the last balancer. It could be that the rubber in an old balancer goes bad (not convinced). If that's the case, I don't think getting another used balancer will fix the problem. Also, I don't want to pay for a new unit, as again, not convinced that will fix the problem. The reason I'm not convinced it is a balancer issue is because Jaguar put out TSB 303-5 describing the problem (as mentioned above).

So, I'm just going to tighten the darn thing up and cross my fingers.

By the way, tightening up the crank to spec is not that hard...According TSB 303-5, which covers this problem:

1) Apply green Loctite 270 to the new bolt, which my local store didn't have. So I bought Permatex Gel Twist Threadlocker Red, which the container claims is really strong. You probably should follow instructions, but unfortunately, this is something I'm not terribly good at !
2) Lock up the crank with a tool designed to do so...I used a bar that I drilled out so there is a bolt going into the balancer on one end and the bolt from the lower tensioner wheel on the other. (If I can find the darn thing in my shop! I may have thrown it away in the hope I'd never have to use it again...might have to make another.) You can also buy or rent tools to lock the crank in place.
3) Crank the bolt to 59 lb. ft. of torque. Then keep going another 80 degrees. This is according to the manual and will give you a precisely humongous amount of torque on the bolt. (236-295 lb. ft.)
4) Hope for the best.

 

Let me/us know how it goes! The damper itself looks like it's decent shape, but I'm going to drop print out the TSB and drop it with my mechanic.

This'll be the 3rd tow in two weeks...Glad I upgraded my AAA membership a few weeks ago.

 

If bolt got lose, there is no reason to replace pulley.

 

Well, here's the update and it's not completely happy (though things could be worse!). At the risk of commandeering this thread (apologies) I'll detail the issue:

I tightened up the harmonic balancer with a new bolt and Permatex red bolt locking goo. That went fine. (Photo of wheel brace below).

Next, came the threading of the belt. The belt didn't line up properly on the lower tensioner wheel. Previously, I had shimmed it to make it work and that seemed fine until the belt popped off. This time, I flipped the wheel and everything seemed to line up. (Photo attached...I moved the belt on to the alternator pulley -- I think -- though it's not in proper position in the photo.)

I ran the car in its space at my (sign) shop and all seemed fine. Wandered off to do other chores...Then.....

POP ! The belt came off. I say things could be worse because I shut down the car immediately. The first time it happened, I was on the highway and had to run the car for a couple minutes until I was able to pull off in a safe place. Fortunately, the engine seems to run fine!

Anyway, I'm about to order a lower tensioner wheel. I know there has been a debate about this item...Some have ears and some are smooth. I'd like to get one with ears, but don't think that's original equipment....Any thoughts on this item?

Thanks all. Sorry to be so long winded...Van Owen strikes again !


Home made balancer brace for tightening.

Tensioner wheel at top, alternator wheel below...belt isn't in proper place as seen here.

 

The early cars had plastic pulleys for both the tensioner and idler.The latter originally had a lip that was later discarded by Jaguar (I'm guessing that it was deemed unnecessary due to its being close to the alternator pulley).

TG, your idler looks to be too far forward (you note that you have spaced this out), and the debris on the front of the alternator likely comes from the serpentine. It's important that the plane of the pulley is at right angles to the belt's direction of travel otherwise it will try to run off. As the belt arrives here from the tensioner pulley it's worth checking that everything is plumb there also. Here's a shot taken from as close as I could to the same vantage point (this replacement pulley is a Dayco 89016, as is the tensioner):



Apologies, Sandwich, although it's sort of on topic.

 

No need to apologize here!

 

Michaelh was correct. The idler was too far forward. I purchased a new (also earless) one on Amazon (less than 20 bucks) and put it on shimless.

Car seems to run fine (fingers crossed), just as good as it runs after a wash and wax (which it needs)!

Idler was probably a bit loose before as I have a huge fear of breaking and/or stripping bolts.

This time I was really careful, snugging the bolt a bit at a time until the idler was properly in place, then torquing the bolt to the lower end of the scale at 40 lb. ft. (53 N-M). I'll check the idler and the harmonic balancer in a week's time or so. Perhaps the loose and shimmed idler led to the loose harmonic balancer?

Are you back on the road, Enjoy Every Sandwich? What was your experience?

 

Not back on the road yet, but hopefully soon. I just got the car towed last night, so hopefully I'll have better or at least more interesting news to report next week.

 

Well, car's coming back tonight. The damper has been replaced with the AJ81330 unit that superseded the one that originally came on this car. It has a locking sleeve, so hopefully it won't come loose again.

Maybe I'll (finally) put the new wheels on tonight and go for a drive. Brand new tires, too.

Due for an oil change this weekend. And the u-joints need to be re-lubed. Exterior and interior need a full, 2-day detail. Always something to do...