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1999 Subaru Legacy 2.5L AT 4WD
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Discussion Starter #1
My car has been making a pretty loud whining noise on acceleration for a while now. Even the previous owners had it but were unable to diagnose it correctly. It's been going on for years. I am determined to find the cause. The car only makes this noise when I hit the gas but not when I brake.

Wonder what should be the 1st thing to look at?
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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on your other thread you said it is a automatic.

might be a air leak or a vacuum leak somewhere.

such would make a whirring / whistling noise when you are on the gas and then settle down when you get off and the engine rpms go down. possibly augmented by the engine twisting in the bay.

try opening the hood and putting the car in neutral with the hand brake on and revving it, and wiggling the plastic intake and see if you can adjust the noise.

the brakes run with some engine vacuum and that may also show some causality.

if you have not already done so, round a up a new OEM pcv valve. and install it / get it installed. bad ones can whistle and its part of the vacuum system.
(those get old and gunked up/ springs in them get metal fatigued as they age. ...I have pulled aftermarket pcvs off vehicles that did not even look like the OEM I just bought as a maint part as I had no knowledge if it was ever changed ).
 
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1999 Subaru Legacy 2.5L AT 4WD
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Discussion Starter #3
Thank you! Interesting.. Yes it is an automatic. I read on another thread that Serpentine belt pulley and tensioner might also cause such noise.. having those replaced might be fix?
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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Thank you! Interesting.. Yes it is an automatic. I read on another thread that Serpentine belt pulley and tensioner might also cause such noise.. having those replaced might be fix?
yes,

belts typically like to make more noise when cold, but when you are standing over them they also are the obvious things making the noise. and minor adjustments to the belts augment and fix some of the noises.

on a similar note, sometimes the bearing inside the alternator is the thing making the noise, and you can just cup your hands and cover the holes on top of it without getting them in the pulleys.

_______

but. your description of it stopping when you step on the brake, really suggests something in the vacuum system.
 
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1999 Subaru Legacy 2.5L AT 4WD
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Discussion Starter #5
Thanks a lot for all your advise and knowledge. I didn't even think of checking for a vacuum leak! I will have that checked out in 2 days and let you know. :)
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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26,318 Posts
One more thing: Would this be the correct PCV valve to get from rockauto.com: https://www.rockauto.com/en/moreinfo.php?pk=50431&cc=1389405&jsn=356&jsn=356
this is the OEM and that one is similar. (ones for this particular car have the threads on the narrow end it seems).

keep in mind there are lots of rubber vacuum hoses to be checked also,...on a car this old one may find more than one damaged or dislodged.

https://parts.subaru.com/p/Subaru__/VALVE-COMPLETE-CONTROL/49223687/11810AA000.html

https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias=automotive&field-keywords=11810AA000
 
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03 H6 OBW & 06 WRX Sportwagon
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if the filter box tabs aren't seated in the slots at the bottom of the lower part, it can cause a 'whooshing' noise.
 

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1999 Subaru Legacy 2.5L AT 4WD
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Discussion Starter #9
Engine Noise Mystery..

The mechanic who worked on my Subie today found that the previous owner who neglected the car, drove with wrong size tires on in the back (smaller than recommended) which had caused damage to the transaxle/transmission causing this engine whining noise coming from transmission. Unfortunately it's been going on a for a while..so the transmission is probably damaged. When I bought this car it had 2 different sized tires in the back much smaller than normal Outback tire. Going to find some new tires and see what happens with the noise. He says we can take out the transaxle and have a look at it, service it and hope for the best. Otherwise, the next step would be to replace the transmission. :-( Not excited about that idea since transmission died on my -97 recently which is why I got this new -99 Outback in the first place. It will be hard to sell this car with a whining noise coming from the engine though.. So I guess I will drive it as long as it stays alive.
 
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