ZAW

I recently bought a 2004 545i with 80k miles on the car. I love it, it's my baby. Though, as I was driving to work today I realized the car started sounding like a truck. It sounds as if the car is straight piped, kind of sounds like a 2500hd. The idle seems fine, performance doesn't quite seem there, though i reset the gas mileage for my ride home and i was getting fine mileage. I tried searching the forum to find a similar problem and had no luck. The sound seems to come to be coming from behind the front tire, under the engine. If someone could point me in the correct direction of diagnosing the problem that would be great.

Happy driving

Zac

BimmerFan52

Sounds like exhaust leak. Are you getting error messages? Are you able to read faults?

Suggest you put it on jack stands (or on a lift if you know someone) and get underneath while it is running to see and hear it up close. If it sounds like it is coming from near the engine remove both belly pans before starting the engine.

Wear heavy gloves and safety glasses. After listening and locating the source of the noise you will probably be able to cover a hole or break in the exhaust system and hear the sound change.

Be careful.

ZAW

Thanks for the timely reply.

I am not getting any error messages and that's why I posted here to find out how to start diagnosing my problem.

I will be putting the car in the air and going from there.

Is it safe to assume its an exhaust issue?

deltabox

is the sound coming from the engine bay kinda like a deep bass humming at idle?

BimmerFan52

No, you have to locate the source of the sound. From your initial explanation of "straight pipe" sound I surmised it was exhaust escaping before the cat and muffler.

ZAW

Not a deep bass humming.

I am going to put it on the lift in the early a.m. and that should give me somewhere to start. The sound definitely suggests that the exhaust is coming out before the cat and muffler.

I'll keep everyone updated.

Thanks for all the help

ZAW

Got it resolved this morning.

Turns out the bolts that connect the exhaust under the car had rusted out. The exhaust was fully connected just not tight resulting in an obnoxious sound.

Thanks everyone for your help!

545iMike

Seems like a common problem. Same thing happened with mine. Nuts at the headers to the b-pipe connection rusted completely.