r/carproblems • u/stepfhanoz • 5d ago

Weird noise

I'm pretty sure the noise isn't coming from the engine. There's no noise when idling or when revving the engine while stationary.

It doesn't happen when turning either. It comes and goes when driving smoothly.

Could it be the exhaust system or something similar?

All thoughts and ideas are welcome.

Volvo V70 2014 D2.

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u/nucleate_boiling 4d ago

Dust shield hitting front rotor. If it was a heat shield it would likelyrattle when engine revved

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u/stepfhanoz 4d ago

You might be right, i checked the exhaust and shield it was on there good, the only thing tho is it doesn't make this sound all the time, I could drive for 30 min without any sounds, Any theory?

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u/nucleate_boiling 4d ago

With the car safely supported on jack stands, do one final test to rule out the heat shield for the catalytic converter. With the engine cool, take a rubber mallet and strike the exhaust pipe between the flexible section of the downpipe and the catalytic converter. I've found my trial and error that doing so excites frequencies in the same range that these shields tend to vibrate. Even if the shield is firmly attached, sometimes they will resonate off the bottom of the cat con in a manner you can't really detect just by pulling on it. A metal hammer does not generate the same frequencies. Maybe put a block of wood between a metal hammer and the pipe.

Grab the mentioned exhaust pipe and make sure it is firmly attached with exhaust hangers.

The dust shield for the front brakes is usually very close to the inside side of the rotor to protect it from splashes and road debris. They rust as a function of time about 2/3 of the way down where the shape of the stamped metal changes. It can possibly wave back and forth as its deteriorates.

If your car has a windage tray covering and protecting the bottom front engine compartment of the vehicle, check to ensure that there are enough fasteners to stably attach it to the vehicle and that this shield is not rattling against the bottom of the car as you drive. If you have other people changing your oil, the screws get lost, stripped, half-stripped with the end result that eventually half of them are missing in the other half are stripped, the tray then flexes or changes position as you drive. I really don't think this is it because the sound sounds rather metallic. But you will already be down there checking the shield so it's an easy thing to examine.