whining noise at 3000 RPM?
06-09-2016, 07:23 PM
#1
Rennlist Member
Thread Starter
whining noise at 3000 RPM?
I have been trying to clean the turbo for parade. This car has been primped and gussied up more than some of the girls who attended my sons prom.
I removed the intake the IC and the AC unit to clean. I reinstalled everything and she started right up runs perfectly as before. I decide to rev the engine and around 2900 I begin to hear a slight whining noise coming from the back someplace by 3000 to 3100 it is obnoxiously loud and around 3200 it dies off again. If I hold the pedal constant at 3000 rpms it is a very loud whine. Nothing at 2600 or 3500 if I blip the throttle or hold it constant.
I don't think I did anything differently. I have done this numerous times without issue. This is the first time I have had the problem. I was originally thinking fan bearing but if you stand by the fan and let someone rev the engine you barely hear it from behind it is far louder in the cabin and sides of the car. I would also expect it to be less rpm focused and more over the rpm range if it was the bearing. The fan bearing was replaced around 4k miles ago.
All I can think of is some harmonic frequency causing something to vibrate but it is impossible to trace the source alone. I'm stumped for now any ideas would be helpful.
I removed the intake the IC and the AC unit to clean. I reinstalled everything and she started right up runs perfectly as before. I decide to rev the engine and around 2900 I begin to hear a slight whining noise coming from the back someplace by 3000 to 3100 it is obnoxiously loud and around 3200 it dies off again. If I hold the pedal constant at 3000 rpms it is a very loud whine. Nothing at 2600 or 3500 if I blip the throttle or hold it constant.
I don't think I did anything differently. I have done this numerous times without issue. This is the first time I have had the problem. I was originally thinking fan bearing but if you stand by the fan and let someone rev the engine you barely hear it from behind it is far louder in the cabin and sides of the car. I would also expect it to be less rpm focused and more over the rpm range if it was the bearing. The fan bearing was replaced around 4k miles ago.
All I can think of is some harmonic frequency causing something to vibrate but it is impossible to trace the source alone. I'm stumped for now any ideas would be helpful.
06-10-2016, 01:21 AM
#3
Rennlist Member
Maybe try loosening the A/C belt tension?, and see if still makes the noise (as you said possible fan bearing). Maybe the tension is now different & thus making the noise only when at that 3k rpm.
As we spoke, you know I just replaced my belt, so I had all that off too. Since it was a new belt, the spot where the A/C unit "was",.. is no longer the same, so I tightened it so the belt has the same deflection as before (1/2"). But I'll have to start er up to see if it's doing anything similar to yours.
Can't wait to meet you & drool over the Cobalt up at Parade.
=Steve
As we spoke, you know I just replaced my belt, so I had all that off too. Since it was a new belt, the spot where the A/C unit "was",.. is no longer the same, so I tightened it so the belt has the same deflection as before (1/2"). But I'll have to start er up to see if it's doing anything similar to yours.
Can't wait to meet you & drool over the Cobalt up at Parade.
=Steve
06-10-2016, 10:36 AM
#4
Rennlist Member
Thread Starter
Well thanks for the ideas guys but I think the car is messing with me.
Went and started it this morning and the noise is gone. Not sure why it was there and even more perplexed to why it is gone but I am not complaining. Last thing I wanted to do was waste time taking it all apart again after all that cleaning.
I don't think I can get it any cleaner. I was going to replace the shell sticker but I have three copies and none of them are the same as the original. All close but larger and although the fonts are correct none of them are identical and I would rather get dinged for a .1 then replace an original that isn't that bad.
Counting down. Should be a great time and lots of people I know will be there. We need to find a place for dinner Saturday. I have about two dozen or so people that want to get together. There should be many very nice cars there as well. I am looking forward to judging 964/993 preservation class. Can't think of anything better to do on Father's day weekend then look at a bunch of well preserved Porsche's especially my favorite models and of course meeting new friends and old ones in one place.
Went and started it this morning and the noise is gone. Not sure why it was there and even more perplexed to why it is gone but I am not complaining. Last thing I wanted to do was waste time taking it all apart again after all that cleaning.
I don't think I can get it any cleaner. I was going to replace the shell sticker but I have three copies and none of them are the same as the original. All close but larger and although the fonts are correct none of them are identical and I would rather get dinged for a .1 then replace an original that isn't that bad.
Counting down. Should be a great time and lots of people I know will be there. We need to find a place for dinner Saturday. I have about two dozen or so people that want to get together. There should be many very nice cars there as well. I am looking forward to judging 964/993 preservation class. Can't think of anything better to do on Father's day weekend then look at a bunch of well preserved Porsche's especially my favorite models and of course meeting new friends and old ones in one place.
06-10-2016, 07:00 PM
#6
Addict
Rennlist Member
Rennlist Member
Well thanks for the ideas guys but I think the car is messing with me.
Went and started it this morning and the noise is gone. Not sure why it was there and even more perplexed to why it is gone but I am not complaining. Last thing I wanted to do was waste time taking it all apart again after all that cleaning.
I don't think I can get it any cleaner. I was going to replace the shell sticker but I have three copies and none of them are the same as the original. All close but larger and although the fonts are correct none of them are identical and I would rather get dinged for a .1 then replace an original that isn't that bad.
Counting down. Should be a great time and lots of people I know will be there. We need to find a place for dinner Saturday. I have about two dozen or so people that want to get together. There should be many very nice cars there as well. I am looking forward to judging 964/993 preservation class. Can't think of anything better to do on Father's day weekend then look at a bunch of well preserved Porsche's especially my favorite models and of course meeting new friends and old ones in one place.
Went and started it this morning and the noise is gone. Not sure why it was there and even more perplexed to why it is gone but I am not complaining. Last thing I wanted to do was waste time taking it all apart again after all that cleaning.
I don't think I can get it any cleaner. I was going to replace the shell sticker but I have three copies and none of them are the same as the original. All close but larger and although the fonts are correct none of them are identical and I would rather get dinged for a .1 then replace an original that isn't that bad.
Counting down. Should be a great time and lots of people I know will be there. We need to find a place for dinner Saturday. I have about two dozen or so people that want to get together. There should be many very nice cars there as well. I am looking forward to judging 964/993 preservation class. Can't think of anything better to do on Father's day weekend then look at a bunch of well preserved Porsche's especially my favorite models and of course meeting new friends and old ones in one place.
