[longtermproject]

2006 325i automatic 130k miles

(Issue)
Started noticing a loud tapping sound that sounds like its coming from the firewall area. Its loud enough that you can hear it over the radio played at normal listening volume.
Air conditioning turned off, the noise starts when I hit 35 mph, and increases with speed, but stops when I slow down below 35 mph.

(What I've found so far)
So far, I found 1 bolt missing in the under shield on the chassis, probably from when a shop removed it to clean after replacing a broken timing cover bolt. The valve cover plastic piece appears to be missing several of the bolts as well, it seems to move quite a bit when I wiggle it.

Has anyone experienced anything like this?

[longtermproject]

Adding to what I've done to figure out what this issue is:

Removed the plastic engine cover, still hearing the noise though it sounds like its slightly less severe.

- No check engine lights
- Nothing appears loose in the engine bay

Noise is still occurring at 30+ mph;
- putting in neutral has no affect
- revving engine has no affect
- ac on/off has no affect

I'm completely lost as to the sound. Would it be more helpful if I uploaded dash cam footage so you guys can hear it?

[Noir]

check the heat shield
maybe hitting the drive shaft

[desertman123]

Originally Posted by Noir

check the heat shield
maybe hitting the drive shaft

Make sure no one zip tied your drive shaft lmao

[Wolf 335]

Drive shaft hanger bearing.

Number 7 in diagram.

[Noir]

Originally Posted by desertman123

Make sure no one zip tied your drive shaft lmao

LOL
when I had my clutch done, that might as well have been the setup. Heat shield was hanging off and making scary noises

[Phyrexia]

I still think it's something flapping. If it was related to a rotating assembly it would change frequency with respect to either engine or wheel speed, but it doesn't.

[longtermproject]

I have results!

It was the upper windshield molding. Sometime over the course of a couple days, the middle of the windshield moulding cracked and caused the flapping. Its amazing that the sound definitely appeared to be coming from the engine bay. Thanks for everyones help!

[Milehighbmw]

OMG.......This same thing just happened to me. I'm traveling from Colorado to Florida. I started hearing this tapping noise. I creeped to the nearest exit. Started inspecting everything opened the hood lifted the car to get underneath spent 2 1/2 hours. Found this thread and rolled my eyes. Found a 3 inch piece of windshield strip loose. Still didn't believe it. Drove down the street and the noise is gone.

I went as far as checking my torque converter bolts swearing the noise was coming from the transmission area. Crazy.......

[NickU252]

I just had the same thing happen, I thought the fan belt was frayed and whipping around the engine compartment. I stopped to check and limped it home thinking it was a mechanical problem. Popped open the computer to find this thread, ran outside and sure enough, the window gasket was dry rot and loose. I'm so glad that it wasn't something expensive.

[2007Frank328i]

So glad i found this post, i never would have believed it. Same happened to me. Loud, scary tapping noise at 65 mph and up. Sounded like it was under the hood. Checked and secured everything. Even went under the car. Removed the old wind shield molding and viola, all is well.

[Spaininator]

This thread just saved me a bunch of time and money. I've been stressing all week investigating under the hood trying to figure out why I was hearing slapping coming from the dash/firewall. It only happened when I let off the gas, evertime I accelerated it would go away. Makes sense why I couldn't recreate it while parked. It just started up after I had it serviced too, so I thought someone messed up by using a wrong filter or oil type.

[Donethat]

I had the same thing happen on the expressway, sounded like steel balls let loose in the motor. Only to be 5” of windshield moulding flapping around.

[cptnobveus]

I know it's an old thread, but I spent most of the day trying to figure out where in the hell the sound was coming from. I was about to take off front passenger wheel or drop exhaust and shield or???? I just couldn't pin down the location. I jacked up the car, disabled dcs and got the speedo up to 40 with no damn clicking/tapping. I sat down and re-worded my google search and it brought me to this post. Earlier I noticed the upper windshield rubber was lifted 3 inches and 2 inches missing. I ripped it off and went for a drive, sound gone. Thank you, thank you.