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Check engine buzzing sound Turbo XT
02-08-2016, 11:00 PM
Post: #1
Check engine buzzing sound Turbo XT
Our 2005 Subaru Outback Turbo XT has 90,000 miles. It was purchased through a private sale. Turbo was replaced by seller about a year ago, but car then sat for a year. We just put new brakes on, replaced a CV axle and two coil springs. Car has been running fine; only premium fuel. Yesterday check engine light came on; buzzing noise when we accelerate to 40 mph+ (started about 5 min. before the check engine light came on). Auto Zone checked code and computer says "no code found". Any ideas?
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02-08-2016, 11:53 PM
Post: #2
RE: Check engine buzzing sound Turbo XT
You'll have to describe the buzzing sound, when it happens, and where the noise comes from so we can better help. It could be the turbo itself or maybe just a rusty heat shield on the exhaust system farther back. Location of the noise is everything in this case. Also note if the buzz changes pitch with RPM or only kicks in at a certain engine speed, which is more typical of a rusty heat shield.

As for the check engine light, they come on for a reason, so maybe the guy at Auto Zone accidently cleared the code by pushing the wrong button on his scan tool? If nobody cleared the code manually it should be in memory for at least 50 starts. This potential code may or may not be a clue to the other situation.

BTW, good chance they were not using a full function scan tool but a "code reader" which may or may not give you all the necessary info. Next time the light comes on and they hook the scanner up you should ask that question.

Post more info and we'll see what we can do.
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02-09-2016, 12:29 AM
Post: #3
RE: Check engine buzzing sound Turbo XT
Thanks so much for responding. It is a light buzzing sound. It sounds like it is somewhere under the hood...maybe front passenger side? It is easy to hear but not loud. It often doesn't kick in until 70, after which it remains present for the remainder of the ride regardless of the speed, but only when the car is accelerating. It increases in intensity based on the amount of acceleration.
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02-09-2016, 12:43 AM
Post: #4
RE: Check engine buzzing sound Turbo XT
OK, the key here is to see if you can duplicate it in the driveway while someone else listens around for the exact location. Normally a buzzing turbo changes pitch with load. (race the engine or "power brake" against the transmission for short periods) A buzzing heat shield will come in at a particular engine speed and you can make it change or stop buzzing by pushing on it with a tool. (something so you don't burn your hand) It could also be a bad bearing on one of the idler pullies for the drive belt. If it's in a hard to nail down location you can listen closer using a piece of hose (heater, vac, etc) with one end up to your ear and feeding the other end around till you find the source. Do not hold the hose tight to your ear. A sudden bump or moving part will blow you away. Hold that end in a closed fist and hold the fist up to your ear leaving a slight gap.
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02-09-2016, 05:59 PM
Post: #5
RE: Check engine buzzing sound Turbo XT
(02-09-2016 12:43 AM)Rupe Wrote:  OK, the key here is to see if you can duplicate it in the driveway while someone else listens around for the exact location. Normally a buzzing turbo changes pitch with load. (race the engine or "power brake" against the transmission for short periods) A buzzing heat shield will come in at a particular engine speed and you can make it change or stop buzzing by pushing on it with a tool. (something so you don't burn your hand) It could also be a bad bearing on one of the idler pullies for the drive belt. If it's in a hard to nail down location you can listen closer using a piece of hose (heater, vac, etc) with one end up to your ear and feeding the other end around till you find the source. Do not hold the hose tight to your ear. A sudden bump or moving part will blow you away. Hold that end in a closed fist and hold the fist up to your ear leaving a slight gap.
Thanks. We can't get it to make the same noise when it's parked. We took it for a drive this afternoon. Check engine light still on, but driving just fine. When I reached 70, there was a humming sound (not as much of a buzz) from about where the turbo charger is followed by one pop about as loud as popcorn popping. I set my phone to record the noise, let up on the gas, then got it up to 70+ again several times, but with no noise this time. I drove it for about 15 minutes more at 75, and no more noise. Slight burning oil smell coming from the front grid area. Oil level is good though.
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02-09-2016, 10:09 PM
Post: #6
RE: Check engine buzzing sound Turbo XT
You may have to hunt around the bottom to look for minor oil leaks, which may not be related at all. If that's a 2.5 liter engine they mount the oil filter in a pretty tight space and they are not always snug enough to be drip free. IOW, that part might be an easy fix.

Back to your noise / buzz... I have heard some weird sounds from a tired AC compressor, which would be running if you have the defroster selected. You might try your next test with the heating system completely off just to verify. You could also switch it on / off to see if anything changes.

One last thought for the moment: Do you have a set of jack stands so you can run in gear at 70 MPH with all 4 wheels up? The car is AWD so you MUST have all of the wheels off the ground.
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02-09-2016, 10:15 PM (This post was last modified: 02-10-2016 06:37 AM by Garner.)
Post: #7
RE: Check engine buzzing sound Turbo XT
I would suggest taking it to a shop with a Full Function Scanner and have a complete scan preformed. Record all of the code NUMBERS, post those numbers here for review, and have the codes cleared. Knowing the code numbers could help us to figure this out much quicker.

Thanks for using the forum,
Garner

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02-10-2016, 06:36 AM
Post: #8
RE: Check engine buzzing sound Turbo XT
Another thought. Did you check the transmission fluid level after replacing the CV axle? Make sure to look in the owners manual for proper checking procedure. If it's an automatic it usually involves warming up the transmission and having the vehicle sitting level. Some are checked in Neutral and some in Park, so you need to know which one you have. But having a low fluid level could cause a noise and trigger the CEL. That could also be why Auto Zone couldn't find a code. Transmission codes usually don't show up on their Code Readers where they will with a Full Function Scanner.

Please keep us posted at to what you find.

Thanks for using the forum,
Garner

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