Test drive ?s

[BS87]

Test drove another 325i today, automatic, and noticed some things, mainly these two i have questions on:

At 2300-3500 rps, there is a rapid "thump thump thump" from right around the gas pedal area.

Also, after the test drive, what sounded like a low hum/buzz could be heard from the rear diff/ exaust area. Any hints as to what might be up?

[bkelsey86]

The buzz or hum was probably the electric fuel pump which is mounted right under the car, unless you heard the sound coming directly out of the exhaust pipe.

[Jand3rson]

Re: Test drive ?s

Test drove another 325i today, automatic, and noticed some things, mainly these two i have questions on:

At 2300-3500 rps, there is a rapid "thump thump thump" from right around the gas pedal area.

Also, after the test drive, what sounded like a low hum/buzz could be heard from the rear diff/ exaust area. Any hints as to what might be up?

Not sure about the thumping, could be some front suspension issues.

As for the buzzing, that's usually indicative of a bad fuel pump.

[DSchultz325e]

thump thump thump sounds like driveshaft trouble. you should spend a while with the car to make sure you pinpoint where and when the sounds occur.

[hotghias]

you'll never forgive yourself if you get an auto. at least, i wouldn't.

[bkelsey86]

If it makes you feel better I'll forgive you........but I'd still put a 5-speed in it.

[Ryan Stewart]

At those RPMS in every gear or just in starting off? If its in first as you start to accelerate its probably a bad u-joint in the dirveshaft.

At every gear its obviously at or in front of the flywheel.

Buzzing has been covered.

I would more than forgive you if you bought an auto and converted it to manual. You basically are correcting a manufacturing defect and should be commended for it, except TJ. :D

[BS87]

My Cabrio is an Auto, and the only reason i settled for it was because the engine, tranny,top, and suspension bushings (urethane) all had <17k on them, and i got a decent price. I have half the parts for a 5 speed in the basement, waiting for spring and warmer weather :twisted: .

I thought fuel pump also, but the buzzing was with the key completly removed. I couldnt exactly pinpoint it, but i am sure the genearl area is to the left side, near the muffler/diff.

As for the thump, i only noticed it in 1st, and once in 2nd(under hard acceleration), but it's possible i might have missed it in 3rd. The sound was near the pedals (kinda where your shin would rest), and did sound like it was coming from the tunnel.

[BS87]

Drove it again today, and the thumping is only in 1st and 2nd gear, aformentioned RPMs, and only above half open throttle. If you keep it below that it wont do it.

[arnoldgtr]

Driveshaft center bearing. Classic symptom.

[BS87]

Huh, never thought of that, as the noise is so far up.

[Axxe]

When the CSB wears out (the rubber around it) it makes the driveshaft alignment go out of whack, hence the thumping. My parts car was doing the same thing, and the rubber in the CSB was completely gone but the u-joints were good.

[Brew]

Also check the flex disc and bolts to make sure they are torqued down properly. I had the same thumping noise in my car and it turned out to be 2 loose bolts on the guibo.