high rpm whine

[lockout240]

Hello all, this will be my first time posting so if i dont have it all right i apologize. Also thank you in advance for all the helpful info.

I have a whine that starts at 5600rpm and continues up to as high as i go with it. The noise sounds like a belt hitting plastic(covers removed), but also has a slight metallic sound to it. There is also slight vibration felt through the gas pedal. There is no power loss, no knock, and boost is not affected. While under load i have not seen an oil pressure drop, but, I took it to the place that tuned it for an experienced dsm opinion, he heard the noise and said it sounded like a balance shaft bearing spinning (motor doesn’t have them) and this time, at a stop, the noise was accompanied by an oil pressure drop of about 1/16in. Since he mentioned a bearing, I took the pan off to check the rest. I found absolutely no metal in pan or drained oil, no evidence of excessive heat or anything else indicating bearing failure. Im a student at an automotive school and had a teacher verify this for me. I also had bubbles on dipstick,????? is a 6 bolt supposed to have a whipping tray??????????, but i think this was due to to much oil. I lowered the level and the bubbles are gone except for one or two. The motor has about 5000m on it, I have not revved it that high very many times due to the whine and side mount. The times i have where on race gas and the car sounded and felt(0 knock/15psi) great until 5600 when the whine begins, then it sounds bad,still no knock though. The noise is also the same under partial throttle and low boost.
Any tips on what other info to include would be great.
Thanks

 

[blackbyrd]

Have you checked the turbo for shaft play? I've heard them "whine" before.

 

[lockout240]

The turbo is a brand new 16g. It has very little side play and no end play, the car also doesnt burn any oil. It does sound like a rotational whine simalar to that.

 

[lockout240]

I still have not found this noise but many other opinions have said it doesnt sound like anything motor related. I've heard alternator bearing, something vibrating at a certain frequency, and a few other things. Does anyone know if tensioner or idler pulleys would make this noise and last this long, also, the bolt is missing from the bottom of the intake manifold bracket. Iwill fix this tonight and post the result.

 

[Locke]

If you have any brand new accessories, they tend to whine during the break in.

Its not the sound of a boost leak, is it?

Is your radio on when this whine occurs? If so, Turn it off and try again. If it is coming from your speakers, the rectifier bridge in your alternator is likely going out. Check this with an o-scope at the shop. a 1uF capacitor bridgine power to ground in your radio circuit will help ground out the AC from a bad rectifier. Non-surpressor plug wires too would cause radio whine also..

Check that your accessory sheeves are aligned. If they are out of align, the belt can wobble, making a whining sound, and could also brush against other things, also making noise. (I know the Water Pump sheeve was a pain to get on correctly on my old 1g)

Check the belt tensions for proper deflection. Again, belt wobble.

Check the bearings in all of your belt-driven accessories. Take tension off the belt (or remove it) and check the pullies for play. Alternator, Steering, AC, Water Pump.

Use a stethoscope, try to locate the area the noise is coming from.

Hope you find it. Good luck.

 

[blackbyrd]

Have you checked your harmonic balancer? aka Your crankshaft pulley? The rubber separates and it can make an almost wining noise..

 

[viperlp01]

you know what i have a nt and at about that rpm my engine starts to make that sound. i have a 420a and im sure you have the 4g63. it kinda scares me but i'm guessing it isn't your turbo if my car does the same thing. if you find out what it is let me know. your not the only one with that whine.

 

[boosted92laser]

I have a whine whenever under boost. But I know that is my turbo, my seals are going bad. I get a nice puff of smoke out the tailpipe whenever I shift after boost.

 

[lockout240]

I finally got to home depot to get the right bolt for that intake manifold bracket. I borrowed a wrench and put it together in the parking lot.

I tested it on the way home and couldnt believe my ears, the noise was gone. It ended up being the certain frequency vibration opinion, which I really dont know anything about but im sure there is some kinda crazy explanation for how it happens.

Thanks for all the sugestions, I definitley apreciate it.