Hi, I have a 2006 xkr (x150) that was in the garage to have the idler pulley and belts etc done as it was squeaking when cold. I had the updated set put on that isn’t prone to the squeaking on cold starts as advices in the Jaguar technical bulletin JTB00045.

After getting the car back I noticed on startup (mainly cold) there was now a slight non rotational plasticy clicking/knocking sound for a few seconds while the car warmed up.(as heard in the video where it’s raining)

I took it back to the garage and they found the auxiliary belt was not running true on the pulleys for a short period on cold start in the morning only. They found a noisy alternator bearing with slight play in the pulley, and found roughness in the auxiliary belt tensioner pulley and idler pulley. So they replaced all the pulleys with issues and replaced the alternator. However a slight ticking noise from the auxiliary belt persisted on cold start.

They checked the operation of the power steering pump, crankshaft pulley, and the ac pump which seem to be working fine and all pulleys seem to be running true. I got the car back and the noise returned but much worse as can be heard in the second video and got to the point where it wasn’t just happening on cold starts in the morning. The car also developed what seems to be a misfire as the car shudders as it idles just after starting. The engine fan also comes on at max for about a minute after starting the car then it returns to normal.

I’ve taken it back to the garage and they are struggling to figure out why it only does it when the engine has cooled. They have replaced the water pump and the power steering pump to no joy. I’ve been told the belt is riding up on the alternator pulley as the engine starts when cold and as it warms it aligns itself and proceeds to works fine. Their next steps are to do the crank pulley, as it’s the only part that they think would be affected by the change in temperature. I was wondering if anyone has experienced anything like this before or has any ideas of what the issue could be before going ahead with such a big job.

 

Oh dear, I'm afraid that your garage are totally out of their depth. Can I ask how much have they charged you for this load of nonsense?

The usual reason for the squeaking / chirping belt, assuming that all the pulleys are OK, is that the OEM belt has a smooth / shiny flat surface which wears even smoother and often develops the squeak as it moves around a little, Changing the idler pulley for the revised version with flanges is a good idea but doesn't stop the squeaking. The first, and cheapest thing to do, is to ditch the OEM Dayco belt and fit one with a rough / textured surface like the Gates version.

If it still squeaks, you need to look which pulley is causing the problem but that's a simple job and definitely doesn't need the parts cannon to be fired. Unless the start of the knocking is pure coincidence, I suspect that the garage have fitted something incorrectly, which, to be honest, is what 99% of garages do. Either way, they need to determine the source of the knocking rather than flailing around.

Richard

 

The squeaking was completely resolved the first time, all the parts for that job have also been replaced again at their expense incase anything was faulty. The issue is that belt now rides up on the alternator pulley, on cold starts (or even when the car has cooled off partly), but once it warms up it fixes itself and runs completely fine. I haven’t been charged anything yet and it’s a conversation that’s still to be had since the issue started after the original work that was done. The garage has been in contact with other specialists around the U.K. who haven’t been able to figure out the cause either. The knocking is coming from the belt riding up on the edge of the pulley, they just can’t figure out why it’s coming out of alignment only when the car is cool.

 

sounds like an accessory drive belt tensioner not doing its job.

 

As I said, if the belt jumping was not happening before, the garage must have fitted something incorrectly.

Is the belt riding up towards the alternator or away from the alternator? I assume that they have replaced the routing idler with the newer one with flanges. This is the pulley immediately before the alternator so if it has been fitted incorrectly, it will affect the routing around the alternator pulley.

It is an extremely difficult pulley to change, the most difficult on any car that I have worked on, because the central bolt cannot be removed without loosing the secondary air injection pipework and, in particular, the pump, and one job leads to another. I would not trust any garage to be able to do this job properly so I suspect that they have tried to get the bolt out on an angle and have probably refitted the new one at an angle. It is not correct to do it that way and is almost certainly going to result in the bolt being cross threaded or not fully threaded into the aluminium casting leading to the pulley being out of alignment and also very likely to have damaged the air injection system which will affect the running of the engine.

Ask them if they undid the bolts and released the secondary air injection pump and then pushed the pipework out of the way before starting work on the idler. If they don't know what you're talking about, they have cocked it up.

Richard

 

Unfortunately I’m not sure if it is riding towards or away from the alternator. Would there be a different cause depending on what direction it is going?

They have replaced the idler pulley twice now and it is the newer one with the flanges.

I’ll be sure to ask about that when I next call them.