BMW mystery noise

Woody,

The underside of your car does not look like this might be the cause but please let us know the amount and condition of the fluids from the diff and trans.

I have owned and serviced 2002's, E-21's, E-30's and now a E-36 that have had almost nothing drip from the drain plugs of either or both.

One word of advice, make sure you remove the fill plug on the transmission before you remove the drain plug.

David

Woody,

In the E-36 I use Lucas in the diff and CARQUEST Synthetic ATF in the trans.

The response to this mix is going to be fun.

David

jr02518 wrote: Woody, In the E-36 I use Lucas in the diff and CARQUEST Synthetic ATF in the trans. The response to this mix is going to be fun. David

I think that's what it calls for: ATF in the gearbox and 75w140 in the diff, assuming it's open and not LSD. You can probably sub a light gear oil (5w30?) in the box if you're so-inclined, but I'd just use what's specified.

Before you put new fluid in it, I'd pull the speedometer speed sensor out of the diff cover. It's magnetic and will pick up any metal debris in the oil. It will be a good indicator if one of the diff bearings are going bad.

How about a very small exhaust leak, does it have an asbestos ring gasket(s)?

Or perhaps a vacuum leak from a hole/crack/whatever ?

BMW in Bridgeport seemed to have reasonable prices when I picked up a few things from them for my E36.

You should be able to reuse those fancy ring gaskets.

Woody wrote:

dj06482 wrote: BMW in Bridgeport seemed to have reasonable prices when I picked up a few things from them for my E36.

Rough neighborhood, but I'll keep that in mind.

Heh, it's right off route 8, not that rough. I buy stuff from them all the time.

I'd avocate for Redline D4ATF in the trans and 79W90 if the diff is open and 75W140 if LSD.

Also, accelerate to say 60 or 70 at the top of a hill, neutral, engine off, coast. Noise? Clutch in, select a gear. Noise? Isolating the input shaft and throwout bearing.

Remove all 4 wheels and examine the brake pads closely. Clean and lubricate the caliper pins while you're there. Noise?

Good excuse to get an LSD?

Harvey wrote: Good excuse to get an LSD?

A shorter final drive with limited slip is the best present you can give your BMW. Hopefully that's your noise, so you can justify it.

Did you find a solution?

I have no idea where the noise is coming from, but on my e30 (which has a very similar suspension set-up) when a wheel bearing started making noise it was much more noticeable when loading that side of the car. The driver's side bearing was bad and it would get much louder when turning right. Also once it failed, the noise got louder by the minute.

I would think you would still be able to hear a wheel bearing while coasting and in neutral.

Is it possible to recreate the noise while on a lift or jack stands? Then you could get under there with a stethoscope and poke around.

I've had more than one BMW with some degree of transmission whine. I don't recall seeing that you changed the trans oil, but I may have missed it; in any case, if you haven't, I'd change it and see if it affects the sound.

Sounds more and more like a diff to me.

On the lift, you may be able to drag the parking brake and have a helper use a bit of throttle to simulate loaded driving.

Woody wrote:

2002maniac wrote: You should be able to reuse those fancy ring gaskets.

Not sure about that, but I may try anyway. Here's what $64 worth of exhaust gaskets looks like:

Say hello to my good friend ultra copper.

Little smear of that stuff seals exhaust parts right up, reuse the crush gaskets no problem.

Before you throw a pump at it, pull the passenger seat and access panel. Have a buddy to drive while you put your ear next to the pump. I think VDO makes the OEM part. The E46 VDO pumps are about $150. At least they're easy to change as fuel pumps go.

Woody wrote: In reply to Tyler H: According to my Bentley shop manual: The fuel rail in the M54 and S54 engine consists of one fuel line, with no return line in the engine compartment. I don't know a lot about pulse width monitored fuel pumps, but that sure sounds like one to me.

Or it could mean that the fuel pressure regulator is integral to the pump assembly, or anywhere in-line between the rail and the pump.

Yeah, the FPR could be at fault. Probably due to be changed anyway (come to think of it, mine's getting up there as well).

Something air cleaner air filter related? Sensitive to throttle position,whistling noise? It may only happen at speed when air is being forced into the intake? Put a small funnel in the end of a piece of fishtank tube for a remote listening device?

Have you checked the output bearings on the rear diff?

http://bmwnut.blogspot.com/2006/03/bmw-differentials-part-ii-diagnosing.html?m=1said: A BMW differential's most common wear item are the output bearings. Output bearing wear is characterized by a hum or whine from the back of the car that will become audible between 3000-4000 rpm, usually more noticealbe in fifth gear at a constant cruising speed. The noise will stop or change when you lift your foot from the accelerator pedal and may also change as the suspension rebounds from dips and valleys in the roadway. The perceptability of the noise is dependent on the load on the bearing The noise may also stop entirely above a given rpm. Also, many cars with differentials showing this wear have gone another 50,000 miles with this noise and no further, so it's not necessarily something that needs to be addressed right away. But the longer you let it go, the more likely it is that other parts, such as the expensive ring and pinion gears, may wear out as well....

Woody wrote: Next suspect: There are two sets of non-serviceable u-joints in the driveshaft assembly. Repairing them means swapping in a remanufactured driveshaft.

Are they non-serviceable because they're staked in? Rockford makes replacement u-joints for this style where the clips are on the inside of the joint. I don't see the Z3 listed but maybe you could call them up.

http://rockforddriveline.com/replacem.htm

Mind if I ask how much you shelled out for the Z3? I'm looking at post facelift (2000+) Z3s right now.