Hello all! New member here, and I wish I was introducing myself under better circumstances. My 2003 STR, 103k, has recently developed a terrible knocking sound on the driver's side part of the supercharger. Almost as if it's off center inside there and the lobe is hitting something. I first noticed the sound about a week ago, but now it's very loud and sounds much worse. Can anyone watch this little video and shed some light on what's going on in there? You can hear the engine idling fine underneath the supercharger rattle. Power doesn't seem to have changed, though I haven't pushed the car since hearing the sound. Thanks for any help!

 

Ya that doesn't sound good at all. What gets me is that it isn't rhythmic. I'd start by taking the intake tube, and top of the s/c off to see if there is anything wrong with the rotors.

 

Yeah, there's a rattle and then just random knocking, with no sort of timing to any of it. I'll take the intake plenum off and see if I can peek down inside.

 

Bummer.........

 

Yes. Yes it is.

 

I'd do it right away. Whatever the noise, is, it's bad and will get expensive quickly. A quick test is to take the SC belt off and run it. If it's quiet, they you are! and if not, the engine has an issue. the other benefit of this method is that you can turn it by hand and feel how the bearings are. The engine will run fine with the belt off, just make sure it is fully removed from the car before you start it.

 

This is going to sound weird - but get underneath the car and check the flex plate for "play" (try to move the flex plate front and back) or any hairline cracks. You could have a loose (or worse missing bolt to the TQ) or the flex plate itself could be cracked.

Any hairline crack is going to make the flex plate "flex" at idle. With the power that motor spits out - it would take a toll on both the flex plate and TQ mounting bolts.

The sound is eerily familiar to my 95 Trans AM - LT4 pulling about 430 HP at the rear wheels. Literally torn the flex plate apart (found cracks along the circumference of the flex plate mounting bolts)

Good Luck.

 

I believe that I had just read an ad here in the for sale for a replacement supercharger if it turns out to be the problem. Here is one on ebay for $600.0 or OBO http://www.ebay.com/itm/2003-JAGUAR-...323b4d&vxp=mtr

Have you tried the screwdriver to the ear stethoscope yet? If you are unaware of this, take a screwdriver put the blade part to the SC and plant your ear to the handle part, remarkably you will hear what is going on inside.

 

I went out just now to try to remove the SC belt, but I'll be damned if I can find a straight path to the pulley down there. It's a tight fit amidst all the hoses that run across the top. What's the trick? Is there a preferred angle of attack to get to the pulley? And I just need a 1/2" square, right? It looks like I need at least a 24" bar to reach it though! Any tips?

 

It may be best to remove the coolant tank first. Once that is out of the way you will be able to see where to place your pry-bar/tool into the tensioner pulley. Once on the tensioner pulley, it is not really hard to pry and then get the slack needed to remove the belt.

You'll be able to spin the s/c by hand to hear if the noise is still present. If you can't spin it with your hand -- you've got a big problem.

 

That's the thing, I began to remove the coolant tank but it looked like I had to drain it to completely remove it. The hose at the very bottom leads me to believe that. I don't want to drain the coolant, because I want to start the engine with the SC unattached to hear what things sound like on the engine alone. It looked like just maybe I could go in from the driver's side with a long enough bar.

 

Unfortunately, it's next to impossible to drop that belt without removing the expansion tank first.

The lower hose is held on by a metal clip that slides off to the side, be careful not to drop it!

There is a special tool found in auto parts stores, called a serpentine belt / pulley tool, perfect long flat bar to release the tensioner, very useful here,

I don't think you absolutely have to start the car at that point, the pulley will be within reach, should spin freely, and be able to help rule out the supercharger as the culprit of that noise,

 

You don't have to remove the tank but in order to do it your going to need another person with a long rod to push the breaker bar into the socket.

 

If the engine is still making power you might have a bad coupler on the SC. They are plastic and they do come apart.
.
.
.

 

If the engine is still making power you might have a bad coupler on the SC. They are plastic and they do come apart.

But you need to follow the advice of taking the belt off first and FAST! I would not start the engine anymore until the SC belt is off. You can drive around with out the belt with no problems.

Other than a very slow STR!
.
.
.

 

Thanks for all the responses and help. As soon as I get home and get the belt off I will report back with what I've found. And let's say for discussion sake I need a new supercharger, should I replace with the exact model used, or is there an upgrade out there that will fit that I can find used as well?

 

You need the exact replacement. Mainly for it to bolt up correctly.

As you might have read we have been hoping for a twin screw upgrade for several years and it's still not out yet!!

You might also consider getting yours rebuilt. And you can always put a smaller pulley on it if you want.
.
.
.

 

Ok, so it's not the supercharger. That I am sure of now. I removed the supercharger belt, and the pulley spun freely, as seen here:

I then started the car, and the sound was as loud as before. If you listen closely, it's almost two distinct sounds: A clicking, like a really really loud fuel injector, and a loud mid-range clunking sound. From underneath the car the clicking isn't as apparent as the clunking. Perhaps the flex plate, as someone mentioned earlier, is in fact at play here? Listen:

I am at a loss. Any one have any thoughts now that the SC has been ruled out?

 

Like I mentioned before - get under the vehicle with a strong flashlight - check the flexplate for hairline cracks and missing/loose bolt to the TQ - so you can rule that out also.

Good Luck.

 

So just to be clear, that last video with it running was with the supercharger belt on or off?