xupkid2

Hoping the brain trust can help me come up with some ideas on where to go next in my search of a noise.

I have a 1995 993 and just dropped the motor to replace the clutch/pressure plate (Sachs), RMS, lifters, Fister Stage III mufflers, reinstall AC and replace all belts. After getting the motor back in I am now noticing what sounds like a whirring or low whistle noise when driving. I do not believe it was there prior to the work I did but Im not certain as the car is fairly new to me and I always drove with the windows open since I didn't have AC.

The noise starts around 2k RPM and continues to 3200 or so. It is associated with RPM as my MPH has no impact. If I am on it hard I can't hear it. Since that RPM range is my cruising RPM it is extremely annoying. The noise doesn't sound like anything is scraping. Its a specific note that it makes and just gets louder or softer depending on RPM in that range.

It does not seem to be transmission related as I can hear it in neutral and at a standstill, just not quite as apparent. The noise is mostly heard from the interior of the car as I can not hear it from the engine compartment. I have the RS belt conversion and checked belt tension. That is not it. I also do not have the belt sensor.

At this point I'm at a loss for what it can be or what else to look into. Any thoughts?

BTW, I have used search for a similar situation and come up empty handed.

Thanks
Brian

Foxman

Sounds like you did some really nice work on the car! I'm guessing it might just be one of the belts - maybe one too few or too many spacers? You indicate that you cannot hear the noise from the engine compartment, but do you have someone on the throttle between 2000 and 3200 to hear it?

xupkid2

Correct. I can hear it when in the drivers seat at a light or on the road. I then get in my garage and open the engine compartment. I can see the tach and push the throttle cable to get into the rev range I need to check. When I listen from the back of the car I can't hear anything.

AOW162435

Clutch & pressure plate are definately the correct parts? Almost sounds like something clearancing itself in the bell housing...



Andreas

pp000830

Exhaust or engine sheet metal or under tray cover rattling?

Foxman

Good thinking Andy. There's an exhaust shield which typically gets removed when installing Fisters. It's pictured below. This could be the culprit if your mechanic opted to leave them on.

xupkid2

Thanks for the info on the shields. Are they the ones that are riveted in place? I was the mechanic in this case so definitely didn't remove them

FisterD

Heat shields are only removed when doing ceramic coating. These Stage IIIs have no ceramic, so heat shields are probably on like they were before conversion.
Does it sound like alternator bearing maybe?
Did you change the engine mounts?

bruce7

Which motor mounts do you have?
Is the sound there when the AC is on or off?
At what gear/speed/rpm is it most noticeable?
Do you have the cabin fan on or off?

bruce7

One more question, do you have the standard shift linkage or is it modified?

uberlawyer

Just a stupid idea, but it did happen to me 2 weeks ago: I could hear a noise when revving the engine from the inside, but nothing when standing in front of the engine bay.

It turned out that the noise came from the speakers. I turned the radio off, and the noise disappeared. I can only assume it was some sort of short-circuit or interference, as I had just meddled with things under the passenger's seat.

Again, a very long shot, but true story.

mpruden

Funny - I was going to say the same thing, but though it too crazy to post. Same thing has happened to me as well. After power cycling the radio, the sound never returned.

xupkid2

The engine mounts are rs mounts so I'm beginning to wonder if it's like the noise from a solid trans mount on my race car or a cup car. It's like that but the pitch of it doesn't change based on rpm. Only happens between 2-3k rpm and gear doesn't matter. I hear it in 3-6 as 1-2 gears are too quick. It's def not through the speakers as that is a separate noise that I can hear.

xupkid2

I've been trying to resolve this one for a while now. I was able to hear it from the engine compartment vs only hearing it in the interior. I was able to determine that the sound appears to be coming from the fan/alternator area. Because I have the RS conversion I thought that the only thing it could be is the alternator, maybe a bad bearing. As a result I replaced the alternator. Problem is the sound is still there. Im now beside myself as to what it could be.

Any thoughts/suggestions would be greatly appreciated.

Thanks
Brian

bruce7

Have you tried to eliminate the AC as the cause by removing the AC belt?