Update on the wailing banshee in my 240D
 

Hey guys,

I started this thread a little over a month ago when I was looking at this car. I ended up buying it and based on the posts in this thread, thought the problem was the speedometer cable. I finally got around to dealing with the issue (there were more pressing ones) and haven't solved it, but I have more information. First, the quick recap of the issue:

The car runs great, but it makes a loud whistling/shrieking/wailing-like-a-banshee noise. It only makes the noise when the car is moving and it's doesn't seem to be tied to the engine. If I rev the engine or put it in neutral as I'm moving along, the noise does not change. When at a stop and idling, there is no noise. After the car has been running for a long time (half hour or more), the noise stops and doesn't usually return the rest of the day. So if I stop somewhere for an hour after the noise has stopped and then drive again, the noise does not appear.

Now for the update:

I had the car at a shop for some exhaust work and mentioned the noise to them. A mechanic took it for a spin and determined the noise was coming from under the car, about where the armrest between the front seats is. He put it up on the lift when he returned and sprayed some lube on the part he suspected. He said "there are some replaceable parts in there, but I don't want you to do that until we're sure that's the problem". He told me to see if the lube took care of it and if not, to bring it back. Well, there was no noise on the drive home. It had been making the noise right before he sprayed the lube and wasn't making it after, so I thought he'd solved it. But the noise returned the next day.

So.....does anyone know what part(s) is causing the banshee noise?

Thanks.

I suspect your mechanic could tell you what he lubed. I also suspect it was the centre bearing on the driveshaft. Anyways just ask your mechanic what he lubed.
Once damaged the centre bearing could do exactly what you describe. Unless he tried to reverse lube the speedometer cable that is. There is very poor capilliary action if he did the cable from underneath the car. You would have to get flow from the top of the cable with lubricant to do it properly. I cannot think of any other components in the area you describe that might temporarily respond to lubrication from underneath. Although I could be missing something.
Cheap problem if you do it yourself. But read about replacement of the centre bearing in the archives. If you have the mechanic do it make sure he marks the driveshafts before separation. The average mechanic already knows the importance of retaining the balance. If you happened to get one that did not you might have a lot of grief. Not really a big job either.

My 1980 240d did same such noise, it was brass bushing in rear of speedometer that the cable inserts into. bushing gets dry causes howling noise. Three drops 3&1 howl free 1.5 years. any more oil might wick into speedo. Hope this helps. Regards Otis

May be a worn speedo cable
 

I haven't had a speedo cable howl for many years, but yes, they sound terrible and can suddenly stop on their own when they warm up. If that is truly the problem, it will come back and get worse until eventually the cable breaks. Lubing the cable will fix the problem for awhile.

Many of our speedo cables have not been greased since the cars were made.. The proper way was to remove the centre cable from the housing. Clean the residue of old grease off and apply new lubricant. A thin grease like lubriplate is probably okay. Then install it back into the tube. Everyone posting is right. A dry cable can make horrible noises. A lot of them also tend to stop the noise after the car is moving awhile.

The howling coming from the center of my dash would be my mother-in-law. I wish!

Hmmmm....after reading Barry123400's post and reading up on the driveshaft center bearing, I was convinced that was the problem. But a lot of people seem to think it's the speedometer cable. I'm hoping for the speedometer cable because that seems like a cheaper and easier fix. Certainly worth looking into before going after the center bearing. So are people suggesting the noise could be coming from the non-gauge end? When the speedo cable was first suggested, I ruled it out because I determined the sound was not coming from the dash/instrument cluster as I originally thought. You'll have to forgive my ignorance here, but where does the other end of the speedo cable connect? Is it easily accessible? Seems that an easy test would be to temporarily disconnect it from the back end and see if the noise stops.

Speedo cable terminates at the transmission. The cable could produce a howl from any portion of itself.

So I could just unattach it from the transmission and take a drive to see if the noise has stopped. Any problem with that approach?

whining from center vents
 

mine makes that noise when the temperature selector is on all the way heat. If I spin it cooler it goes away... But I live in FL, so the noise is only when it is cold.