Rattling/Metal Noise when stepping on gas pedal

lcc014 · Post by **lcc014** » 22 Feb 2020, 20:16

Starting from yesterday driving home from work, I heard a rattling/metal noise from the front. Whenever I accelerated the car, noise happened. When my foot off gas pedal, noise disappear immediately. It wasn't that loud yesterday afternoon. Today, it became more louder whenever I stepped on gas pedal. I lowered driver side window when rattling/metal noise happened, Even my wife could hear it when all windows were up. I could hear the noise when driving no matter windows up/down. It became very loud when I accelerated up hill. So noise level was proportional to the acceleration.

What could be this rattling/metal noise ? Car drives fine, no fault codes. I don't feel any shaking or vibration when driving or when braking. Just this annoying rattling/metal noise.

Thanks,

Ching-Ho Cheng

Post by **abscate** » 23 Feb 2020, 06:13

Two most like candidates

Loose metal plates under car touching exhaust , or perhaps axle shafts

Brake backing plates slightly bent out of position and touchingwheels

Post by **scot850** » 23 Feb 2020, 08:08

Abscate has listed the probable candidates. Heat shields are prone to falling of as the mounting holes react with the steel mounting bolts and washers which eats a hole through them.

Other thing to add to the list the exhaust heat shield broken mounts.

Neil.

lcc014 · Post by **lcc014** » 23 Feb 2020, 16:00

Thank you for the suggestion. Brake backing plates are all gone on both side of the front brake for a long while. So, I will put the car on ramp to check for any loose heat shield.

Ching-Ho Cheng

lcc014 · Post by **lcc014** » 26 Feb 2020, 08:11

I drove the car onto ramp and checked around under the front of the car. Nothing loose. The heat shield above converter was tight. Then I started the car while car was on ramp and heard the noise of exhaust was not quite "right/normal". Sound like a leak but not very loud. Then I drove the car last night with front windows down (driver and passenger). I could hear the loud sound from the front during acceleration - exhaust, not rattling/metal. So most likely it was the exhaust leak, exhaust manifold ? The exhaust from converter to the tail pipe was "new", not too long ago, about 1 year old.

Post by **bmdubya1198** » 26 Feb 2020, 22:17

Is your car turbo? If not, remove the exhaust manifold heat shield and check the flexible portion of the exhaust manifold. I've seen them rot out and leak, causing a LOT of noise.

lcc014 · Post by **lcc014** » 27 Feb 2020, 06:17

Mine car is NA. I did look at that flex portion of the exhaust manifold from underneath, seems fine. I did not remove the heat shield from above to check. One thing though the wire mesh wrapped around that flex elbow had been long gone for a long while.

Post by **scot850** » 27 Feb 2020, 07:49

Have you tried tapping the muffler system with a small hammer to see if you can make the rattle appear?

Neil

lcc014 · Post by **lcc014** » 28 Feb 2020, 17:21

Muffler is "new", replaced last May. @bmdubya1198 hit the bull eye. It was the flex elbow of the exhaust manifold. I will have Volvo garage to replace the manifold.

Thanks,

Ching-Ho Cheng

Post by **bmdubya1198** » 28 Feb 2020, 19:33

Glad you found it! My cousin's old NA wagon had a nasty leak from that section of the manifold, it made the car sound very rattly and raspy.