rattle when accelerating

[lacrawgator]

I have a 2018 3011ds Forester. Recently I have been hearing a rattling noise while accelerating. When I let up on the gas it stops. It doesn't seam to affect the performance of the engine. Any thoughts.

[A32Deuce]

I have one at certain RPM a resonance vibrates one of the exhaust heat shields. You can tap them and maybe hear it, but I haven't found it yet.

[emm-dee]

I had the same issue. Went to local Ford dealer who said it was fan belt. I didn’t see any way that could happen but, sure nuff, when they replaced the belt under warranty all the noise went away. FWIW, mine made lotsa noise when cold but when at normal temperature it only did it at 2,000-2,150 RPM.

A quick check you can do at home is to remove the belt and start the engine. It’s easy to remove and, obviously only run it a very short time.

[Kirk S]

I'm assuming the engine is a Ford V-10?

It may be predetonation (spark knock). Try some mid-grade fuel and see if it goes away if the previous suggestions dont work.

If you get it resolved please let us know how.

[emm-dee]

Originally Posted by Kirk S

I'm assuming the engine is a Ford V-10?

It may be predetonation (spark knock). Try some mid-grade fuel and see if it goes away if the previous suggestions dont work.

If you get it resolved please let us know how.

That was my initial thought when my V10 started making the noise. I used to have Corvettes before the age of electronic ignition controls so I definitely knew the sound of predetonation.

Ran the fuel down really low and then filled the tank with premium fuel. No change so tried a few different additives with no success. When the shop manager told me the fan belt was the problem I looked at him like one would look at someone who just told you the earth is really flat.

Apparently there’s a problem with the fan belt being out of balance. This causes it to generate a vibration the makes the heat shield rattle. Sounds logical because a cold engine makes more noise. As the fan belt heats up it stretches and generates less vibration.

[AquaMan]

Some heat shields will break a weld at the mounts and cause a rattling, and banging on them may not produce any sound. Had this happen on a Jeep.

[doc73]

Had a few timing chain issues on my Fords as well. Causes a rattle under acceleration.