I wanted to change the serpentine belt yesterday on my 03 Type S V8 so dove into it. Man, what a pain trying to get the bolt out of the tensioner. Why couldn't Jaguar just make the clearance behind the tensioner a little bit wider so that the belt would slip through. After continually ripping the inside of my arm against the radiator shroud so it now looks like a hunk of raw steak, I finally gave up. The bolt is stuck in there good and there's not much room and I don't want to strip it. Probably best to get it out from the underside. I have a lift in my garage but it was tied up with another dead car for the day so I'll get at it again next week.
It's more of a job than I thought.

 

I hate serpentine belts and the lack of room to get at them in all vehicles these days. Unless you're Tiny Tim, it's damn near impossible. And with huge hands like mine, forget about it. I always end up asking my small-handed buddy up the street for help....

 

Why are you removing the bolt? The tensioner has a square cut out for a 1/2 drive. Use you breaker bar and back off the spring and then slip the belt off. The belt can be changed without removing anything but it is a tight fit. If you search you can find the step by step instructions.

In fact even the STR super charger belt can be removed this way.
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^ yup ^

 

So you're saying that the belt can be slipped off behind the tensioner. JTIS says to remove the tensioner, even so I did give it a halfhearted try to get the belt behind it but there's very little clearance in there. That would make it a lot easier if you don't have to remove the tensioner bolt. As I said, the bolt is really tight in there and I didn't want to either strip the flats or damage the radiator or rip any more skin and meat off of my arm and hand.