I had a noise from the top of my motor at idle that went away after it warmed up. I took off the supercharger belt and noise went away. I wanted to replace the pulley anyway so I removed the supercharger and replaced the snout bearings, installed a solid coupler and a smaller pulley. It is now a lot louder and makes the sound continuously at idle, goes away when above 1200rpm or so. I removed the belt again and noise gone. Checked for play (as in coupler failure) and its tight. Almost sounds like the back of the supercharger is where the noise is coming from. Any one have this problem and or know what may have happened? I have heard the smaller pulley will make the normal noise louder but this is a loud "box of rocks " sound.

 

Rear bearings are also known to wear out, chances are this is the case as will with yours am afraid.

 

I am afraid you are right although the timing just does' not make sense. This noise only happened after I worked on it. Does anyone have a link for replacing those bearings. Oh and a place to buy them for a reasonable cost?.

 

Some noise might have been already there, overshadowed by the rattling . The rigid coupler will enhance some rattling again; there was a reason that the spring was used in the original coupler.

There are plenty offering them on the web, here is one for instance:
https://jonbondperformance.com/

 

Undo the top V8 plate, no need to disconnect from the water supply simply undo the 4 bolts and lift it forward, take a look at the rotors, if the rear bearings have broken up they often chuck their needle rollers into the housing and you will see debris or chunks missing

 

The X350 doesn't have the same "V8 Plate" as the XKR's & earlier X308 XJR's, but it's not too complicated to get a look inside the supercharger.

- Intake pipe/tube off, loosen the top hose clamp at the throttle body only.
- Remove the hose clamp for the bypass hose from the s/c to the throttle body.
- Remove nuts & bolts from the duct seals.
- Loosen the 4 bolts that hold the outlet duct in place (but don't try to remove them, they have captive nuts on the inside, if you completely remove them the nut will fall into the s/c, not good.)
- Wiggle the top plate from side to side to get the duct seals out.
- The outlet duct plate will just lift up from there.

 

I have taken the plate off of it and it looked ok inside. Rotors still had coating on them and very little play. Again above 1000 RPM's noise goes away. I do hear more noise from the back of the supercharger though. I was wondering about the solid coupler combined with the smaller pulley making it loud. But this is a solid box of rocks sound steady like rotors not growling like bearings. Also when belt removed and supercharger is spun by hand it is smooth and no noise heard or felt. Do you think it would be worth a try to put a torsion coupler back on? I must note that this is the smallest pulley made for this the 2-3 lb one. Snout was machined properly and plenty of clearance.

If torsion coupler would make a noticeable improvement I would give it a try. Does anyone know where to source one for a reasonable price? I definitely don't wan't to put the original one back on with 90k on the clock.

Has anyone else out there had this pulley installed with similar symptoms?

 

I have changed a couple of super chargers that only make a bad noise at idle, I would be surprised if it was the rear bearings from your description, normally when these start to fail the coating on the rotors starts to get removed as the rotors start to touch each other

 

I am beginning to think it is a combination of things as it has been running like this without any change for 2 weeks.
1) solid coupler
2)smaller pulley causing less tension on the belt
3) I am using a gator belt made by good year(supposed to be quieter)
4) normal wear for this age.
This still does not make me happy and I can't stand the noise. The car does feel to have more mid range throttle response though.
If I am right, does anyone have an idea how to quiet it down? I refuse to believe other people have not had this happen with this pulley set up.
one more thing I put GM supercharger oil in it, is there any better oil ? I keep thinking if there was a tighter tolerance between the gears there would be absolutely no play and I would bet no noise.

 

I had the rock sound before I had mine rebuilt (it actually ended up being an exchange). I now have the smaller pulley and am using the belt that was on there. Before I sent it off to get rebuilt I popped the top and held the vanes and could turn the snout pulley about a 5th of a turn. I'm sure the bearing were going from the sound and that was on a stock S/C.

 

If you hear loud rock noises but when you turn the supercharger by hand it's smooth, I suggest turning the idler and tensioner pulleys, one of them may be failing. If you had bad bearings in the SC, you would feel some roughness when turning by hand. The front bearings in the SC are lubricated by a bath, so unless the oil bath is low, th efront bearing shoudl be okay. The rear needle bearings are lubed permanently so they could be dry. If the rotors are tight, this is probably okay.

 

In looking at all the rebuild kits for this supercharger on Ebay, it seems that the rocky noises are indeed snout bearings or the coupler as this is the symptom mentioned in each kit literature. I haven't had one of these apart but the rebuild doesn't look too bad if the guys that sell the kits are accurate in their descriptions. They pretty much al agree that by 100K, the unit needs a rebuild.

 

Could it be the hose at the back of the supercharger going to the ecu

 

ok, again, new bearing and a solid coupler were installed with a smaller pulley(the one that requires machining to the snout) A gatorback belt by goodyear(highly recommended on this site). now make way more noise. Stethescope to the snout, no noise, same thing on both the tensioner and idler. noise is gone with supercharger belt removed. Noise comes from the middle to back of SC and goes away above 1200 rpm. below that sounds like a rather large box of rocks. Engine has full boost no loss of power(actually runs rather strong with the new pulley mid-range, about the same on top end, about what I had expected)
I am really thinking I screwed up by going with the smaller pulley and solid coupler.

 

XKR Brian - I modified my snout and installed a smaller pulley about 2 years ago. A few months ago I started hearing a very worrisome "box of rocks" from the supercharger so I figured the because of the smaller pulley I now needed to replace the snout bearings.


I rebuild the shaft and installed a solid coupler and the supercharger spun freely but I could hear a tiny "clack" noise when I rotated it back and forth a few degrees in each direction which I thought was the free play in the front gears. The rotors showed 100K of oil film with some wear to the coating but no scoring to the inner casing.


Reassembled everything, fired her up and what did I hear: Bigger Bag with more Rocks - louder than ever. Horrible sound. Stethoscope confirmed that the noise was not from the snout but from the rotor housing of the unit only I couldn't tell if it was from the front or the rear. I knew I could change the rears myself but, that I didn't have the tools or skill to do the fronts and reset the rotors, so I was hoping it was the rears.


Ordered new rear bearings from JonBondPerformance ( my M112 uses the rear bearings that easily press out) and took everything apart again. These rear bearings are easy to change and as soon as I pushed the rotors into the new bearings I could feel the difference and when rotated by hand the tiny "clack" noise was now gone.


Reassembled once again, said a prayer, and started the engine. No Bag of rocks. Still noticeable mechanical noise from the solid coupler but nothing like before. Surprisingly, it has become even quieter (about 1500 miles) since then and is now as quiet as when I 1st got the car (at 78K) even with the solid coupler.


Changing the rear bearings on mine was easier than rebuilding the snout. I just wish I had done it the 1st time

 

Thank you for that reply. At least I dont feel as bad. The time line on how mine happened threw me for a loop, but with that being said, I will now order the rear bearings and replace. My noise does come from the rear of the supercharger, i have very little almost no play at all. No noise above 1200 rpm and almost silent @1000 rpm.

 

I have a 2001 xkr 3rd gen m112 I believe. How difficult is it to change the rear needle bearings. What tools do you need?

I assume an OTC 4581-3 and slide hammer? Do you need to grease the new ones once fitted ? if so what grease

Thanks
Simon

 

if your supercharger bearings look like this you don't need a slide hammer or any special tools to change them. Also, the new bearings come pre-greased

 

Hi, did you ever get this sorted? I'm currently in exactly the same position as you described in this thread. Noisy supercharger, did the new snout/pulley upgrade/coupler, only for the rocky rumbling noise to be certainly no better, possibly worse.

I had a tiny amount of of play on one of the main shafts, it would click/knock if I wiggled it, I was fairly sure it was the main bearings not the needle bearings.

But with the advice above to go back and change the needle bearings I wonder if you did it and whether it made any difference?

Cheers.

 

Hi all,

As an update to my own post I cracked and spent this weekend re-doing the whole removal of supercharger job so I could replace the needle bearings to see if they were causing the rocky rumbling noise.

Well... success.

The replacement of the needle bearings has returned my car to a car that sounds normal. No more noise it tickover.

Lessons learned:
If you're gonna spend the time to remove the supercharger to replace the snout bearings, do the needle bearings at the same time, it's only an extra £45 for the bearings and about 30 mins to swap them out. Saves going back and doing it all over again!!

It's a lot quicker to do the job a second time, it took me about 20 hours the first time as I struggled to follow the instructions step by step. This weekend it took me about 10 hours as I knew what needed doing and what NOT to bother doing. Also knowing where all the awkward bolts are and what tool best gets to them helps immensely.

If anyone wants a more detailed list of things to consider when doing this job let me know and I'll post some notes up.