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Q: Just bought a used Forester that started rattling when I'm not accelerating and the wheel is straight. Any ideas on what it could be?

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When the car is started and there is no acceleration I can sometimes hear a rattling noise coming from the right side of the car, between the engine and the wheel somewhere. If I accelerate at all the noise goes away. Also, It only seems to rattle if the wheel is straight, most the time turning the wheel one way or another reduces or eliminates the sound. The noise is there regardless of gear, but when going from N to R or to D the rattling sometimes gets quieter while gears are changing but returns to normal intensity once the gear is set. (Sometimes the noise is uneffected by gear changes) The car also pulls very slightly to the right. And... If I turn the AC on I do notice a change in the rattle, but can't tell if I'm just noticing additionally noise from AC. Regardless though the rattling doesn't happen ever when I'm accelerating

My car has 150000 miles.
My car has an automatic transmission.

A: Hey there. The most common source of rattle...

Hey there. The most common source of rattles on Subaru's are the exhaust heat shields. They can rattle under all sorts of random circumstances. Whenever you turn, accelerate, let off the gas or brake, the motor experiences torque that is dampened by the engine mounts so the passengers won't feel these vibrations. This torquing will affect the exhaust as much as any other component on the car. Checking for exhaust shield rattles is fairly simple. Use a soft mallet hammer to tap on the shields to see if it rattles. If it does, repairing this is more challenging than locating it. It's a creative process that can only be decided in person. Of course, you will need to get under that car to access all of the shields.

Other than the exhaust shields, it could be a dust shield on the brakes or a sway bar end link. Both of these are far less common as determined by your description of your symptoms. If it is a sway bar end link, it will rattle most often when you go over bumps. If it is the brake dust shield, you will need to remove the wheel to see if the shield is loose.

If you need further help having this done, a certified professional from YourMechanic can come to your car's location to diagnose the rattling noise so that this can be corrected.

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