I recently fixed the brakes on my car, and now my car is making a loud rattle sound when I am idling, and also when in neutral. The car has 100,000 miles on it. The RPMs also drop while it is rattling. When I shift into first gear, the RPMs pick back up and the rattle goes away. I have heard that this model has a heat shield rattle, but it is winter where I live. I am assuming since it is affected while idling, it is related to the engine or transmission. Any thoughts?
There are several causes for the engine to rattle while idling. With your car, the heat shield or an under engine shield is most likely. The other causes are the AC compressor clutch, idler pulley, or belt tensioner. The heat shields are used between the exhaust and the underside of the vehicle to keep the vehicle cool and the heat from the exhaust directed out of the tailpipe. When the heat shields become loose, they can make a flapping noise when the vehicle is moving. To verify this, a qualified technician, like one from YourMechanic, will be able to diagnose the rattle and replace your heat shield if necessary.