Sounds like a siren

89 240DL Est manual. When I set off after standing overnight there is initially no problem but build up speed to around 25-30mph a sound like a war time air raid siren (spooling down and towards the end of its running) begins and continues for perhaps 5 to 10 minutes and then goes away. It dosn' always happen and sometimes when it does it suddenly stops for a short time and then starts again. I suppose its something that lacks lubrication. I have had all the levels checked and they are ok. I suspect a wheel bearing and presumably as the rears are lubricated by the axle oil it makes me think this must be front?
I bought the car five years ago and the following has always been the same. Sometimes after depressing the clutch it 'takes up' without hardly any pedal movement as if the hydraulics have not depressed the clutch sufficiently. The next time I depess the clutch its back to normal. As I havn't had to put any fluid in the master cyl in all this time over 19k miles I can't see that there can be any leaks in the system.
Thanks for any replies in advance.

[93240se]

Does the whining continue if you depress the clutch and let the engine revs die down? Does it continue on "over run" if you ease off the throttle and stay in gear ? It could possibly be the propshaft centre bearing, if it is then remember to change the rubber "doughnut" bearing carrier at the same time as changing the bearing. I had one wear out on my '93 model, gave similar noises. Alternatively could be the alternator bearings on the way out.

Regards, Richard VOC 3801.

Thanks for suggestions. Don't recall that depressing the clutch has any effect on noise but will check tomorrow and get back on this. If alternator bearing can this be lubricated?

[Clifford Pope]

It's always worth trying lubricating something, even if it only makes a small or short-term improvement, because at the least it proves you have identified the culprit.
You don't necessarily have to replace the propshaft centre bearing. Drop the cross member, and try spinning the bearing. That will establish whether it is the cause. If it feels dry or squeaky, you can prise back the plastic cover a fraction and inject some oil. When mine got squeaky this effected a total cure, with no dismantling necessary. It's now done 334,000 miles.

It could be the alternator bearings or the brushes. If you remove the fan belt you can try spinning the alternator, or even drive the car a short distance (but no water pump). Brushes are easy to replace, even in-situ if you are familiar with how they slot in. If you remove the brushes you can then spin it to see how the bearings feel on their own.

I appreciate the further replies, thanks.

I took the car for about five miles this morning and guess what, no noises at all. As I said, its not always happening. Also, the noise only happens when in motion.

If I don't dash out and rip the thing to bits its because I've bought a 850 which I hope to have from 1st Feb and until then I don't want to start things on the 240. Its not that I don't appreciate the help!