I'm figuring it's just a rattle thing but...
Under power as the rpms get up higher there is a clattering sound from under the hood (only when under load, so can't really check parked). It only does it when I'm on the throttle and disappears if I take my foot off the gas. The higher up the rpms - under load only whether steady state or acceleration - the louder and faster it becomes. Again, if I take my foot off the gas it disappears.
The sound is like a tappet that is gummed up or set wrong sounds. The tapping rate increases as rpms go up.

What does supercharger bearings going out sound like? Other than a little annoying, would you think this anything to worry about?

 

The common problem for the sound you describe is either the tension or idler pulley. The bearings go dry. They can be replaced or repacked, I've done both. You cannot rule out a SC bearing though, and on rarer cases, the alternator bearing goes.

Not likely a valve train noise. This engine is set up with buckets and hardened steel shims. It is not a hydraulic tappet setup. I've had lots of these engines apart at various ages and, if shimmed up correctly at the factory the shim clearances really don't vary over the years. Valve seatin seems to have no impact on clearances. That doesn't mean a bucket cannot become stuck in its sleeve if the engine has been really abused - like no oil changes for thousands of miles, etc. I've seen some ugly valve trains on AJ26s because of failed water pumps that caused the engine to run hot for miles and miles before it overheated. The oil cooked in the cam covers and turned to molasses. If you pull a cam cover and find the valve train clean, then I'd completely rule out a stuck tappet.

 

very hard to guess...can you post a vid with sound?

 

The supercharger typically makes some mechanical noise, but only a very small amount--only audible at idle with the hood open.

At higher engine speeds or with the hood closed you shouldn't be hearing any supercharger mechanical noise.

TTYL
David

 

Thanks for the info overall - very helpful. I've replaced enough tensioners that would be the most likely. (it would be very difficult to record.)

 

If it's not the belt system, it may be the timing chains or the VVT units. Uper tensioner problems are typically described as a rattel or clatter. I don't know what car you have but if its early (prior to 2002), look at the tesnioners.

 

Could be detonation. What fuel are you using? Run a can of BG-44K through the fuel system.

 

GOOD POINT! I'll do it.

The only puzzler is that it only does it when on the throttle (if I take my foot off the gas it disappears). It starts in at just over 2000 rpm - and it is getting gradually louder - but too faint to record.

How difficult is replacing the belt tensioner?

I can't find a shop manual for an 05. Would shop manuals for the 98-02 range be close enough generally?

 

Over a year old post, (I know)
-but I was wondering if anyone else could elaborate, confrim/deny any possible soltions to that noise??

Clearly I am having the exact same issue, and thought searching for some answers might point me in the right direction.

Thanks!

 

noises are very hard to diagnose over the forums, especially ones from the engine bay. I see you have an R, and others have said the bearings in the supercharger noticeably get louder as they age, and its normal to hear it. You can have the SC rebuilt, if it bothers you. I do not know, however, how long or how much noise means the SC will fail though...nobody has ever gone that long to report it (that I have read, at least)

 

Proir to my ownership the SC was recently replaced under warrenty. Also at an earlier point, the idler pully and tensioner were redone. I will try to see maybe if something is loose. The indie shop who did all the work mentioned that the mother board may need to be flashed / updated, but he couldn't say for sure.

 

When the car is in Park, the noise does not appear. (as also stated above)
If it was a pully or tensioner, it would seem that the nosie should be present even when in park???

My initial thought was that it may have something to do with the trans??
Maybe a Torqe Converter or somthing??

That is just guessing though!

 

if you've got enough jack stands, get that cars butt (at least) off the ground (don't forget the wheel chocks up front!) and put the car into gear...perhaps put the e-brake on, and then go looking for that noise. Very hard to guess still at this point.

 

I'm having similar problem :-(

check this (the discussions I had so far, not solved yet):

https://www.jaguarforums.com/forum/x...k-noise-54713/