Hello again everyone, after much work, I got my XJS on the road. However I have a new issue, it seems to have decided that one alternator belt per tank of gasoline is acceptable consumption. When I put this last one on, I made sure to tension it properly, a half inch of downward play with moderate pressure on the belt. I then drove the car about 15 minutes, just enough to get it up to operating temperature to check and see if the new coolant sender was functional. When I got home my half inch of play had grown to 3/4 to an inch of play. The belt itself is not damaged yet, but I cannot understand for the life of me why it keeps doing this. I've never seen V belts lose tension, and I can't imagine how they would with a setup like the Jaguar uses. I'm not having this issue with my power steering and water pump belt. Any advice would be greatly appreciated.

Thanks,
Evan

 

Did you tighten the alternator mounts after tensioning the belt? V belts do loose tension, they stretch out with use. I my experience old belts are always slightly larger than new ones. I'd be inclined to retention all the belts after 100 miles or so.

 

I will check the alternator mount, I may have overlooked it. This belt lost tension after maybe 10 miles.

 

Down here, at my last employ before retiring, the "boss" decided to stock some ?????? brand belts.

We had preciously only stocked Dayco/Gates/Bosch.

Money in the eyeballs I reckon.

Weeeeell, the come back rate was terrible. STRETCH, in less than a mechanics "test drive". Dumped the lot, back to basics, never a complaint.

After 55years in Spare Parts, I see the quality, either OE or aftermarket, getting quite sad.

 

I fitted a complete set to my V12 a few months ago. No problems with them. I got them from my local Jaguar dealer H A Fox in Norwich. They weren’t expensive with the discount I get through work.
Rob.

 

Felt like a followup was a prudent decision in this thread for future reference, I retensioned the belt, confirmed that the mounting bolts were indeed tight, and it seems to have held sufficiently since. So I suppose a warning to future members who purchase dayco belts, a rapid retension will be required. Thank you all for your help figuring this issue out.