so why all the sudden when I reinstall my belt is it rubbing against the tensioner ? does something need to be replaced ? I cant imagine this is good for the belt. pretty sure it wasnt like this before. thanks

 

Did it rub before, and what were you in there doing?

 

I don’t recall it rubbing but I’m not sure. I just did the coolant lines replacement. Port supercharger , intercooler and pump upgrade etc etc

 

If it was rubbing, you'd see marks on the tensioner and rubber dust all over the place. Is it the same belt that was on there before you did the work?

And to answer your question, yes, it is routed correctly. But from what very little I can see from here, it looks like the belt may be a bit too short, causing the tensioner to rotate counter clockwise (as you look at it from the front), bringing the belt closer to the tensioner body. Also, please repost the pictures you had in the other thread here for easier reference. Thanks.

 

Hey thank you very much will do !

 

do belts skrink and contract over time I could see that. Its a velocityAP belt I got when I did the programming and tunning but its probably go 40k miles on that belt. What is the smooth pully that has the marks from the belt on it bc I think id like to swap it out while im in the fixing mood. Everything else is grooved.so why not.

 

I have about 65k on my XKR with what's in the sig without issues. Generally belts don't stretch but rather crack. They definitely don't shrink. Don't worry about the smooth idler pulley. Same deal with mine, and again- about 65k without any issues. The ribs haven't worn grooves in it, but there's no paint where the ribs run on it. Also, idler pulleys that run on the outside of the belt don't need (or should have) grooves and/or shoulders to guide the belt; that's what the pulleys before and after do.

My advice would be to call VAP. With only one picture, minimal info, and unanswered questions, you're at the limit of what you can expect to get out of this thread.

 

well I am back where I started. the little tab broke on the new tensioner which has less than 1000 miles on it and my belt is back rubbing on the tensioner. I have even used a little longer belt so it wouldnt be pulled so tight. Surely its not torque from punching on it doing that . Like I said this is the 2nd one. see pic.
[img alt="broken tab on tensioner is that a limiter or sorts?
"]https://cimg7.ibsrv.net/gimg/www.jaguarforums.com-vbulletin/480x640/tensioner_xjr_742ad03bebf09d612092093f660a8b1af9f5 b398.jpg[/img]
broken tab on tensioner is that a limiter or sorts?

 

Maybe the bolt have not been tight enough?

 

Maybe not any help but since your already dealing with VAP. They have released an improved tensioner. Yes expensive at $600 but do read the description as it mentions the problem of the belt contacting the tensioner body.
VAP Upgraded Tensioner
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no they are tight.

 

oh really thanks I didnt realize they had. not really sure I want to spend $600 on a tensioner but ill go check it out for sure and talk to them about it., thats STEEP !

 

Understand 100%! But I was not aware this was even a problem and then BAM VAP comes out with a modified tensioner.
So it is a problem for sure or they would not have gone to all the trouble to produce it.

My feeling is the high cost is due to the very low production numbers they forecast to sell. Hard to make a profit on custom low demand parts.

Another similar thing is the electric vacuum pump modification they offer. Until I read that if you lose vacuum the car is almost impossible to stop! I did not know it was a problem. And it's a real safety problem. The vacuum pump is on the front of the engine so the plastic piping is exposed to mechanical damage if you break a belt.

On other cars if the vacuum is lost yes it's harder to stop but not too bad.
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If you lose a vacuum pump you have vacuum resevoir for 2-3 brake press with assisted brakes and after that brakes will work as un-assisted. In theory brakes still have same brakeforce, BUT driver need quite bit more leg juice to operate them. (both legs in emergency)
Some racecars i raced had an un-assisted brakes and very hard pads - A day in racetrack and then jumping an road vehicle and you think how this can be legal on road: Brakes and steering have no sense of whats going on under wheels at all. Its weird how fast you adapt.

 

I have talked to people that had this happen to them while driving an X351 XJ. You literally can't stop the car.
I hope he see's this and makes a comment but he is a big guy and had both feet on the brake pedal pressing with as much force as he could and said that if he had been going faster he might have wrecked the car. Since it happened around 45 mph he luckily got it stopped.

Anyone willing to do a controlled test? Block off the vacuum supply and see how the car stops?
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I will not test it
(had my share of failing brakes and tyrewalls already)