[F80_M3llow]

whats up guys. i have a 2006 325i with about 72,300 miles.Rrecently i got my muffler delete and after i got that done ive noticed when im at a standstill in park and rev the car up and when the rpm drop back down i hear an intermidate screaching noise coming from the engine then it stops only when i rev the car. whats can be wrong need this figured out before i rip my hair out. anyone please chime in and help me.

[F80_M3llow]

So I have narrowed the noise down from under the car somewhere in the middle. This noise is not coming from the engine. The car runs like a dream. It only happens ewhen the car is fully hot. Like when I drive back from work all highway driving then come to my parking lot throw it in park that's when the noise happens I have no clue what this can be.

[F80_M3llow]

Can anyone help

[martinezjames]

i used to have a 325i same year as yours and i too had a noise coming under the car. i described the noise as a rattle and not as a screeching noise. the object that caused my rattle was a small aluminum support/mounting plate which is located before the secondary cats. that little piece would start rattling when i would start slowing down and coming to a stop after the car was warmed up. all i did was remove it because it really serves no purpose and its in a bad spot anyways. so try taking that off and see if your noise goes away, it goes bad because it heats up and gets wet and causes the screws to rust and worn which makes the plate loose which causes the rattling noise.

[F80_M3llow]

Originally Posted by martinezjames

i used to have a 325i same year as yours and i too had a noise coming under the car. i described the noise as a rattle and not as a screeching noise. the object that caused my rattle was a small aluminum support/mounting plate which is located before the secondary cats. that little piece would start rattling when i would start slowing down and coming to a stop after the car was warmed up. all i did was remove it because it really serves no purpose and its in a bad spot anyways. so try taking that off and see if your noise goes away, it goes bad because it heats up and gets wet and causes the screws to rust and worn which makes the plate loose which causes the rattling noise.

Its really hard to describe. It only happens when the car is fully hot. When I come to a stop or park after a long drive and Rev the car slightly it starts when the idle settles down. I'm really paranoid. I have no warranty and just worry its something in the engine.

[F80_M3llow]

Originally Posted by BMWE90FANATIC

Its really hard to describe. It only happens when the car is fully hot. When I come to a stop or park after a long drive and Rev the car slightly it starts when the idle settles down. I'm really paranoid. I have no warranty and just worry its something in the engine.

It started after I got my muffler delete.

[Slow_335i]

Probably getting a video of the noise will help?

[F80_M3llow]

Originally Posted by Slow_335i

Probably getting a video of the noise will help?

I'm going to try and get it on video might be hard since its so loud under the car.

[F80_M3llow]

Well here guys I took a video. It may be hard to hear it but after u listen to it between 0.05 sec until the idle drops you hear that long vibrating schreech then goes away. It only happens when reved after leting foot of the gas and then you hear that long schreech. Please turn your speakers up or put your headphones on. Please someone help me. I rueled out belts, tensioner and pulleys ect since i changed those. I have no clue where this is coming from 2 days ago i took off the front undersheild and took a peak under the car with no avail. Looked over all my exhaust brackets and tightened them up still have the noise. Really embarassing and im lossing faith slowly. No noise on cold only hot.

http://www.youtube.com/watch?v=cCvLz...e_gdata_player

[zshortyz]

couldn't really tell from the video, but is it more of a whistle sound?

[F80_M3llow]

Well today i got a chance to get a really clear video of this odd noise. If anyone has any info please help me.

Part 1

Part 2

[kiwi29]

The noise for me I found out its near the primary cats/headers that hanger might be welded on but somehow it gets rattles from there. Your best bet is go to a muffler shop and ask them to tighten all the bolts

[F80_M3llow]

Originally Posted by kiwi29

The noise for me I found out its near the primary cats/headers that hanger might be welded on but somehow it gets rattles from there. Your best bet is go to a muffler shop and ask them to tighten all the bolts

Funny thing is it only happens when I fully warm the car up from driving. Never when cold. I ran out of options of what this could be. I'm prying it's not anything to due inside the motor. Fingers crossed

[F80_M3llow]

Hope someone can shed some light on this soon.

[kiwi29]

Originally Posted by BMWE90FANATIC

Funny thing is it only happens when I fully warm the car up from driving. Never when cold. I ran out of options of what this could be. I'm prying it's not anything to due inside the motor. Fingers crossed

doubt it, is it a feint rattling noise when you take off slowly?

[F80_M3llow]

Originally Posted by kiwi29

doubt it, is it a feint rattling noise when you take off slowly?

When I'm driving I can't hear it nor under wot. It's only when coming to a rolling stop, or when I'm in park and lightly rev the car and let off. It happens when the idle settles. This shit is blowing my mind

[kiwi29]

Originally Posted by BMWE90FANATIC

When I'm driving I can't hear it nor under wot. It's only when coming to a rolling stop, or when I'm in park and lightly rev the car and let off. It happens when the idle settles. This shit is blowing my mind

same here, i found out that it only happens from rolling starts that go slow or when i'm slowly balancing out

[F80_M3llow]

Originally Posted by kiwi29

same here, i found out that it only happens from rolling starts that go slow or when I'm slowly balancing out

I took a look under the car last week. Took the undersheild off and inspected the brackets that hold the exhaust. Tightened them up with no avail noise still there. So what were you talking about with that bracket you mentioned earlier next to the headers. Can you clarify a bit more. I might as well take a look at what you were talking about. Thanks for helping me your like the only one that really responded to this.

[kiwi29]

Originally Posted by BMWE90FANATIC

I took a look under the car last week. Took the undersheild off and inspected the brackets that hold the exhaust. Tightened them up with no avail noise still there. So what were you talking about with that bracket you mentioned earlier next to the headers. Can you clarify a bit more. I might as well take a look at what you were talking about. Thanks for helping me your like the only one that really responded to this.

yeah no problem, the same problem drove me crazy af too lol
the first time this happend, i blew my cats out and it was stuff from the inside of the piping this time i went under the car to see it again to find out the welded bolt closest to the front of the car to hold the mid pipes up was loose, i grinded it off and added a new bolt with teflon tape. sorry i don't have pics of where but you'll notice it, it's almost right where the headers and mid pipes connect. what you wanna do to check is bang on the pipe and grip on the places you think is loose and it'll work from then on gl, i might be going under the car again sometime this month to retighten it again

[F80_M3llow]

Originally Posted by kiwi29

yeah no problem, the same problem drove me crazy af too lol
the first time this happend, i blew my cats out and it was stuff from the inside of the piping this time i went under the car to see it again to find out the welded bolt closest to the front of the car to hold the mid pipes up was loose, i grinded it off and added a new bolt with teflon tape. sorry i don't have pics of where but you'll notice it, it's almost right where the headers and mid pipes connect. what you wanna do to check is bang on the pipe and grip on the places you think is loose and it'll work from then on gl, i might be going under the car again sometime this month to retighten it again

how the hell did you manage to blow your cats? What were the symptoms. Maybe mine are shot

[kiwi29]

Originally Posted by BMWE90FANATIC

how the hell did you manage to blow your cats? What were the symptoms. Maybe mine are shot

lol well i race ALOT and i'm usually in a low gear throttle blipping alot and some symptoms are your car throws a check engine light (sometimes), your car seems to go into limp mode(depending on how severe) the car seems slow and gets extremely loud at higher rpms 4k-redline and my favorite, you blow out chunks of shrapnel to a chp officer behind you i highly doubt you blew them out completely like i did but a good way to check is to bang on the cats lightly and if you feel or hear anything jump that's sign 1 and if you rev your car loud and it rattles thats sign two. bmw's cats are ment to last for forever but theres always that chance but if you don't track your car alot, it won't happen

[kiwi29]

Originally Posted by martinezjames

i used to have a 325i same year as yours and i too had a noise coming under the car. i described the noise as a rattle and not as a screeching noise. the object that caused my rattle was a small aluminum support/mounting plate which is located before the secondary cats. that little piece would start rattling when i would start slowing down and coming to a stop after the car was warmed up. all i did was remove it because it really serves no purpose and its in a bad spot anyways. so try taking that off and see if your noise goes away, it goes bad because it heats up and gets wet and causes the screws to rust and worn which makes the plate loose which causes the rattling noise.

this is exactly what i ment lol i just grinded the old bolt off and screwed on a new one