recently, I got a message on my 99 jag xk8 that my battery wasn't charging. so, I started the car ,went to the trunk and removed the ground wire. the car died. ( this was done per work shop manual ):I replaced the alternator and tried putting the new belt on, several times until the tensioner pulley bolt broke. after getting pretty peeved, I got the idea to check the new pulley size against the old one. sure enough, the old one had a smaller pulley. I changed them out and the belt went right on after I put a new tensioner pulley on. so, which is the right pulley and which is the wrong ? the smaller will do more revolutions than the larger that came with the new alt.

 

In the good olde days, which many of us are from, one could test if the battery was charging by doing what you did. But in the modern dayz, there are too many electronics functioning when the engine is running. IMO, you risk damaging electronics. Not saying you did, but if you wanted to know whether the battery was charging, why not simply put a voltmeter across the battery terminals? Anything in the neighborhood of 13+ volts means your charging system is functional.

 

thanks gordo but the jaguar workshop manual was where I was told to do so. I agree that in the old days that's the way we did it. I am so unfamiliar with my 99 xk8 that I have a lot to learn. still my question hasn't been answered. which pulley is the right one ?

 

by the way, I did check with mm

 

I learn something new everyday.

Just like GordoCatCar, I'd have said never disconnect the battery with the engine running and was sure I'd read this advice in Jaguar publications.

Checked in JTIS and found the appropriate section:


(click on the image to enlarge it)

There it is - start the engine. Whilst the engine is idling, disconnect the negative terminal .......

With the pulley, my guess is you didn't get the new alternator from a Jaguar Dealer? If not, that probably explains the different pulley sizes. The drive ratio for the XK8 is specified as 3.04:1 if you are really keen to do some measurements!

Graham

 

Given the new pulley with the old sized belt broke the idler, I would assume the old pulley on your old alternator is the correct size. Somebody with an original alternator on the bench can give you a diameter measurement to confirm this.

Regarding disconnecting the negative battery cable... we know more now than we did back then... even the language is old "whilst running?" Jaguar also advised that trans and differential fluids were "lifetime fills". Today we know lifetime means like 60,000 miles, or so. Personally I think they meant the lifetime of their warranty. :-)