[tamathumper]

I have a recording from this morning, and I'm trying to figure out how to post it, and if it even captured what I can hear. I did verify a "whistle" especially above 3K RPMs, and I also verified that my belt is still at the initial tension setting which was basically just with the tensioner in place, with no turns, so I don't think it's over-tight or adding to the noise. I had posted some black "chuff" on the underside of my hood after the initial installation, and I cleaned that off last weekend and it's not coming back so I think it was just from normal belt wear-in.



But I definitely have a dry, raspy kind of scraping sound and hopefully it's not an idler getting ready to go.

Partial Post: Please Login or Register to read the full post.

[tamathumper]

OK, it took a while to edit and post, but here is the video. Please pay particular attention beginning at :12, where you hear the dry raspy noise begin and continue for the remainder. On the video it sounds like road or wind noise, but it does gets quieter at :24 when RPMs drop to 3500 (yet speed remains the same). That's the sound that has me guessing as to what it is... I did not seem to be able to capture the high frequencies, like the whistle, but it was there. I guess I need a better microphone?



http://www.youtube.com/watch?v=oputpi66khc

Partial Post: Please Login or Register to read the full post.

[flash]

something is preventing me from seeing youtube attachments in safari. going to have to work on that.



there is definitely a metallic sound that is not right. i still suspect the belt was too tight.



as for the microphone, it needs to be in the engine bay for sure. where is it now?

Partial Post: Please Login or Register to read the full post.

[tamathumper]

In that video, it's in the cabin, basically at the position of the camera.

Partial Post: Please Login or Register to read the full post.

[flash]

yeah - going to be hard to get the sounds there. it's very hard to hear exactly what's going on in that recording. it sounds a lot like an idler pulley bearing, but i can't be sure. do you have a stethoscope?

Partial Post: Please Login or Register to read the full post.

[tamathumper]

Not yet, but I'll get one today if you think it'll help.

Partial Post: Please Login or Register to read the full post.

[flash]

i think you can run through the engine bay with it and nail down the source of the noise. that's how i figured out it was the bearing. it has worked on a couple of cars now that had that bearing fail from over-tightening.

Partial Post: Please Login or Register to read the full post.

[tamathumper]

Stethoscope acquired.



Another attempt, this time I shoved my cellular phone under the hood and took off! Google forgive me. The metallic rasping noise is most apparent when coasting at about 4,000 RPMs. I don't hear it as much when revving at the stop light. I think I might have overloaded the mic as my untrained ear thinks it heard some "artifacting".



0:00 - 1:00 - Driving up to 5,000 RPMs; shifting; coasting at 4,000 RPMs

1:00 - 1:15 - Revving at stop light, up to 5,000 RPMs

1:15 - 1:38 - Driving up to 6,000 RPMs; shifting; coasting at 4,000 RPMs



https://www.youtube.com/watch?v=t3LYFh3K1GQ

Partial Post: Please Login or Register to read the full post.

[banditsc]

I think I'm hearing pulley/bearing noise in there, maybe water pump, or even in the alternator, or maybe one of the pulleys in the balance belt area.

Partial Post: Please Login or Register to read the full post.

[flash]

what did the stethoscope tell you? i presume it's a mechanic's stethoscope, which is basically a rod attached to a pair of earpieces. it should be very easy to touch around and find the source of the noise.

Partial Post: Please Login or Register to read the full post.

[tamathumper]

Picked one up today, and just got home and pulled into the garage. Decided to check the other issue (stumble) first, and that might set me back a bit on this. Update in that thread.

Partial Post: Please Login or Register to read the full post.

[Eric_Oz_S2]

Tama - your car actually seems really quiet in comparison to mine. Perhaps part of the issues is the AFM that I am still running.

Partial Post: Please Login or Register to read the full post.

[tamathumper]

I've got a whistling like yours, but it's not loud enough to pick up with a cell phone I guess.

Partial Post: Please Login or Register to read the full post.

[tamathumper]

Using the stethoscope on the idler bolts at the top or the large mounting plate results in a very loud noise - impossible to describe and hard to tell if it's normal or not. Sounds pretty "rough", though. Using the stethoscope on the supercharger itself or any other component of the engine results in much less noise, and is much "smoother". I have no idea how to record that. Maybe I can hold the stethoscope up to my cell phone...



The belt tensioner is still set at original tension, and the belt is "pinging" once in a while, about once every 5-10 seconds.

Partial Post: Please Login or Register to read the full post.

[flash]

at a steady state rpm, there is no reason the belt should hit the belt guard. it sounds like the belt is too tight, and the belt guard is too close to the belt.



the belt guard is supposed to be bent up at about a 10 degree angle, and pulled all the way to the top. there should be a good gap between the belt and the guard.



remove the belt guard to be sure you hear it hitting, and not some other noise.



i have never seen the inboard pulley fail, but i suppose it's possible. compare the sound at the 2 bolts. i'm wiling to bet it's the outer pulley only.

Partial Post: Please Login or Register to read the full post.

[tamathumper]

I can't verify the exact angle on the belt guard as of this moment, but I can verify it's as it was out of the box, no modifications have been made to it. I can probably get a protractor on it tonight if you think it's important. It is definitely pulled all the way up as the instructions directed.



The tensioner is fully retracted, and the belt has not been tightened since installation. By that I mean the belt cannot get any "looser" because there is no way to make the tensioner shorter. I stretched the belt using the method we discussed on the phone, and when it was loose enough to install the supercharger, I used a short bar to pull out on the alternator a bit and slipped it over the idlers and the crank. Would it help if I took a tension measurement? I have the Krikit, the Arnn-Worx and the P-9201 tools if you think any of those would work.



As an aside, I thought it "tinged" when too loose?



I did try putting the stethoscope on both idlers and the sound was the same.

Partial Post: Please Login or Register to read the full post.

[flash]

it does ting when it's too loose, but there should be enough clearance not to ting when loose enough not to take out the idler bearings. does that make sense? it sounded confusing even when i typed it.



again, remove the cover to verify that the belt is hitting it, and that the noise is not the bearings. just before they fail, they make much the same sound.



this would be the first time the inner idler failed.



i don't have a setting for any of those tools, so measuring it wouldn't help me. as a rough reference, you should be able to move that belt in and out by hand about 1/2" at the area down between the alternator and the SC.



if you have a disk sander or something like that, the pulleys are easy to shave down to fit. they are a standard dayco pulley, available at most any parts store for about $20 each. just take .035" off one side and install. i'll get you the part number.

Partial Post: Please Login or Register to read the full post.

[tamathumper]

Agreed, that was a bit confusing - you got me with the second "not" in "not to take out the idler bearings". And, are you using "idler bearing" interchangeably with "idler pulley" or are the idler bearing and pulley (or probably more accurately, sheave) separable?



With a CNC machine, a lathe and a mill in the basement, if I ever have to take a disc sander to something to shave off .035" you have my permission to shoot me.



In any case, I'll take the belt guard off tonight and fire it up to see if it keeps making the "ting" sound, and if I get it in the air, I'll also take a tension reading with the Krikit so that if nothing else, we have a point of reference for the belt tension. It beats a kick in the head. As I recall, I measured the tension and it was about 3/8" as per the instructions when installed.



Do you have a Dayco part number on hand? I can look on the parts themselves tonight if necessary.

Partial Post: Please Login or Register to read the full post.

[flash]

the idler pulley has a bearing pressed in it. technically the pulley is fine, but the bearing is what goes out. i haven't found the bearing separately yet though.



dayco #89095

Partial Post: Please Login or Register to read the full post.

[tamathumper]

Got it.



http://www.summitracing.com/parts/dac-89095

Partial Post: Please Login or Register to read the full post.