What would cause a loud noise and rattleing when you first start car Sounds like muffler is loose maybe Once I get going the noise stops Only does it when it's idleing?

Answer 1

Sounds to me like your heat shield is loose, this same exact thing happened to a friends car a couple weeks ago. As soon as I heard his car I knew exactly what it was. The heat shield is basically just a piece of sheet metal formed in the shape of the exhaust pipe and generally right above the catalytic converter or the front section of your exhaust pipe. It is very common for these to get rusted to the point that the clamps aren't holding on to anything anymore. Or the clamp(s) (usually just like a pipe/hose clamp) just simply vibrated off. The main reason I think it is this piece and not something more major is that you said it would stop after you started driving, if it were a hanger or larger piece of exhaust work this would not be the case. I would save yourself an unnecessary trip to the mechanics and a ridiculous bill, and just check underneath your vehicle ( BUT ONLY DO SO AFTER IT HAS BEEN SUFFICIENTLY COOLED DOWN AT LEAST 30 MINUTES AFTER DRIVING AS THE EXHAUST PIPE CAN GET IN EXCESS OF 1,000*F) I would also recommend wearing goggles/safety glasses and some sort of gloves. Generally it can be fixed with just a screw driver and/or a wrench. Or if you determine that it is this piece but lack the motivation to actually fix it, it really isn't going to hurt anything as long as you can live with the rattling sound.