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I. Silva
I. Silva, ASE Certified Technician
Category: Subaru
Satisfied Customers: 1602
Experience:  auto mechanic
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Recently when accelerating or going uphill, my 04 Forester

Resolved Question:

Recently when accelerating or going uphill, my '04 Forester XS seems to make a high pitched whining or almost a whistling sound. What could this be?
Submitted: 7 years ago.
Category: Subaru
Expert:  Mike J replied 7 years ago.
Hello, automatic or manual? Does the pitch of the whine change with speed of the car or engine RPM's?
Customer: replied 7 years ago.
It's stick shift, and yes the pitch of the whine increases with RPM's or driving speed. The sound seems easiest to create under acceleration above ~3000 rpms. When I've tried to create it in my driveway with the car in neutral and revving the engine, the car doesn't seem to do it nearly as loud. The car has 81,900 miles, but has been very well cared for (regular maintenance, no off road, no extreme temps since I live in LA). Thanks! -Dan
Expert:  Mike J replied 7 years ago.
This is where I would start......If you can hear it sitting still and reving the engine.....remove the drive belt. This will show whether it is a appendage making the noise, such as alt, ac, ps, idler etc.
Customer: replied 7 years ago.
Thanks. That's probably more than I have time to deal with. But I appreciate your help.
Expert:  Mike J replied 7 years ago.
Your quite welcome, without doing some testing I would just be guessing and I dont want to do that. I did pull up the car for any noise related TSB's and there are none listed for your senerio. Good luck!
Customer: replied 7 years ago.
Relist: I still need help.
Customer: replied 7 years ago.
I have more info that may be helpful. The sound is only present when the engine is under at least a moderate strain, such as hard acceleration from a stop light or trying to accelerate up a moderately steep hill. Once the strain is decreased (by letting up on the gas just a bit) the sound goes away. It does NOT seem like the pitch of the sound increases with engine speed. Today I did an experiment: I was going uphill at about 50mph in 4th gear, tachometer at about 3,000rpms and no sound. I pressed the gas pedal about an inch or so and the high pitched whirring sound started. The car accelerated to about 55-60mph and the whirring sound continued until I let off the gas. While maintaining 55-60mph there was no sound, but when I pressed the pedal again, the sound started again. So the sound is only there when the engine is trying to accelerate, not when it's maintaining speed!
Expert:  Mike J replied 7 years ago.

Dan, nice test. So under strain it makes the noise in 4th gear. Sounds like a drivetrain noise coming from the transaxle. If the noise occurs in 4th try 5th or 3rd same senerio.

If the noise is still there have someone check the transaxle. See if the fluid is clean ie. no metal shavings, severe burnt smell.

Customer: replied 7 years ago.
It'll do it in any gear. Just need to have the revs above ~3,000 to 3,500.
Customer: replied 6 years ago.

Mike,

I just got a follow-up email asking me if my question has been answered. Unfortunately it hasn't. I've taken the car to a Subaru dealership as well as an independent Subaru shop and neither one has any idea what the problem could be. I did find other Forester drivers report the same issue on http://www.subaruforester.org/ at: http://www.subaruforester.org/vbulletin/f88/whistle-noise-under-power-58640/.

 

-Dan

Expert:  I. Silva replied 6 years ago.
Hello....Maybe i can help you ....You need to check the exhaust resonator pipe , it cracks right where the pipe meets the resonator (front of it) and also on the same pipe the gaskets go bad and when you step on the gas they sound just like a whistle....Good luck....thank you .....accept my answer if i helped...
I. Silva, ASE Certified Technician
Category: Subaru
Satisfied Customers: 1602
Experience: auto mechanic
I. Silva and other Subaru Specialists are ready to help you
Customer: replied 6 years ago.
Thanks for getting back to me. I'll check it and get back to you!!
Expert:  I. Silva replied 6 years ago.
Ok....Let me know..
Customer: replied 6 years ago.
I think you may be right. But can you tell me where I'd find the exhaust resonator pipe on an '04 Forester? There's a lot of exhaust pipes under there and it seems most of them are covered with heat shields. Thanks- Dan