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Cowbell Noise- 2011 Subaru Outback 2.5i Limited

First time poster, thanks for your help.

Just purchased a used 2011 Subaru Outback 2.5i limited. Approx. 35k miles. No history of serious maintenance issues as far as I (and Carfax) am aware.

The car starts just fine, with no apparent issues or strange noises. Then, once the car is shifted into reverse or drive, I hear a soft but persistent “cowbell/wood block” noise from front (left?) of the vehicle. The noise seems to be agitated by pressing and releasing the brake or accelerator. It gains in frequency with the speed of the car, regardless of whether I am on the gas or just coasting. It is most noticeable up to about 25 mph, when it is overwhelmed by road noise.

Once the car runs for about 20 minutes, the sound is gone, at all speeds. But if the car is parked for about hours, the problem begins anew.

I reported the problem at my last oil change, but because the dealer is over 20 minutes away, the noise is hardly noticeable once I get there.

Although the noise itself is annoying, I am more concerned that it is an early sign of something more significant to come. As you can see, I only have about a thousand miles left on my bumper-to-bumper warranty.

Thanks for any and all ideas you may have.

I would start by checking to see if you have a loose heat shield and/or a cracked exhaust manifold. Noise by either of these items can go away as the engine warms up and the metal expands.

Thanks. Is that something that I (an amateur) would be able to visually confirm?

It depends on how things are setup under the hood. I’m not familiar with your car, but you might be able to see some of your heat shields under the hood, and there will be some you can’t see without getting under the car. There also might be a heat shield covering your exhaust manifold.

You could try dropping your car off the night before an appointment so the engine compartment will be cold when the mechanic checks it out.

I would want to leave it at a trustworthy Subaru tech overnight so that they could hear the noise. Something as minor as a loose bit of the the exhaust system is a possibility. But on a cracked manifold it shouldn’t matter if it’s in gear or not. And loose heatshields and such usually rattle or even sound like grinding - a sharp metal on metal sound rather that something more dull like cowbell or wood.

Anyway, in case it is something more serious, a trained set of ears on someone with some knowledge of Subaru quirks I think would be worthwhile.

I did leave it at the dealership Subaru overnight once. The technician mentioned something loose in the exhaust system, and said that it had been tightened and lubed and should solve the problem. Of course, I couldn’t tell on the way home, because the car was already warm.

The next morning, the noise was back. I hate to be a pain to the service department, so I was hoping you guys could help me articulate a more specific theory when for my next trip to the dealer.

Thanks again!

Since the mechanic already considered exhaust rattle, any alternate theories?

The exhaust system probably has several heat shields on it. The mechanic might have tightened the wrong one or misidentified the one what was rattling. Maybe more than one of them was loose.

Unfortunately, everything we can offer is speculation, which is less valuable than a mechanic’s in-person diagnosis. Perhaps it’s time to try a different mechanic or a different shop.