Annoying flutter noise 89 TII
 

Welp, the car is on jackstands until new parts show up. Trying to get rid of the newest batch of gremlins while I'm at it. One thing is an annoying high-pitch flutter noise. It follows with the RPM of the engine. It's not related to the belt driven accessories (alt, ps, a/c). Engine makes power and boost without issue. This noise just gets really annoying on long drives. I can't pinpoint the noise because the engine has to be running, so I can't take the UIM. Video angle is just to try to get microphone pointed towards sound. Any ideas, let me know.


https://www.youtube.com/watch?v=CJ1l...ature=youtu.be

Perhaps your problem is similar to that being discussed on the FD board (https://www.rx7club.com/3rd-generati...irbox-1131011/).

Have you tested your fan? It could be seized. Try turning your fan by hand. Does the pulley move?

Fan clutch is ok. Without any belts, the ticking is still present. It sounds like it is coming from under the UIM. Gonna use my test pipe for the intercooler and see if I can get a better look before I pull off the UIM and start guessing. At this point, I am guessing something to do with the oil injector spider, vacuum spider, or a noisy fuel injector. More input will still be tried if presented

Edit: New video

I hear it better in that video. Have you checked your turbo shaft play?

It was pretty minimal when I checked about a month ago. I had to add some preload to the wastegate actuator because the wastegate was rattling (BNR stage 2) and checked the play while I was at it. No play at turbine, and minimal (<.010") on compressor side. No rattling as far as I could tell. I could pull off compressor cover and look I suppose. Hope to have some more time to look at it this week.

Are your belts too tight? Also aren't there bearings with the altinator?

Noise is persistent with no belts. There are alternator bearings that do go bad, and I have swapped alternators a bunch because the rats that rebuild them undercut the rotors so they can't accept an off the shelf bearing, and have to use a proprietary bearing. If I have to do it again, I will likely turn some bushings for the rotor shaft to build it back up to where it needs to be so it can have nice bearings.

I swapped out my primary injectors. One was sticking, but it seems to be a separate issue. No issues with vacuum lines. Tomorrow I will pull the compressor cover and have a look inside.

Update on this, and more questions.

So I went and got a mechanics stethoscope because I'm tired of probing around on this. Disconnected PS and A/C belts to reduce noise, and plugged my MAF straight into the intercooler, bypassing the turbo compressor. Then I got to probing. The noise gets louder towards the back of the engine, and is most pronounced when I probe onto the bell housing, and around the rear iron. It gets quieter going from the rear iron to the rear housing, to the midplate. I tried to see if it could be pilot bearing or clutch throw-out bearing, but varying throttle and clutch depression made no difference.

At this point I am suspecting a main bearing/seal issue. I removed the inspection plate underneath the bell housing. The back of the rear iron was damp. Not wet, but damp. Photos are attached.

Changing the oil revealed very thin rubber strips and small metal particulate at the oil filter. At this point, I'm certain a rebuild is needed. What do you guys think? Rear main bearing gone out and taken seal with it? What should I be looking at for the rebuild process as far as parts? The rotor faces all have good compression, engine makes good power still.

I was thinking of getting a seal kit and new main and rotor bearings. What else would I need to get? I would be scrubbing everything of contaminated oil. How much, and what type of sealants will I need?

Looking for a recommended course of action

https://cimg7.ibsrv.net/gimg/www.rx7...7ff14b3320.jpg
https://cimg4.ibsrv.net/gimg/www.rx7...9f39b2be50.jpg

Welp... found part of the problem
https://cimg5.ibsrv.net/gimg/www.rx7...d5a782c8e2.jpg