Tech question: what IS this sound!

[Fastbrit]

Please, no wisecracks, but I am being driven nuts by this weird sound. Deano can testify that it is quite baffling. Today I took my car out for a 280-mile round trip to a show and, sure enough, after about 100 miles, the car starts making a peculiar whining, moaning sound. You can hear it on this video – it starts at about 20 seconds in. The best way to describe it is like the sound of wind howling though wires! Here's the details:

The sound starts, as I say, after the car as been run for some time. Suddenly, for no apparent reason, it starts to make the noise – it's low and not dependent on engine or road speed. To stop it, I have usually just dipped the clutch, blipped the throttle and re-engaged the clutch. It goes away for a while then recurs a short while later. I always assumed it was the throwout bearing BUT today I played around a little more to try and investigate the source. By dipping the clutch, it stops – not instantly, but as if stuff is slowing down – but started again as soon as I let the clutch back in. If I hit the throttle while the clutch was out, it stopped for a few seconds, or even went away for a few miles. BUT it does NOT vary with road speed, OR engine speed and DOES NOT stop when you simply load the clutch pedal, so that's why I'm starting to think it's not just the T/O bearing. If I turn my head to the rear of the car, I can hear it louder (as you'd expect) but it appears to be louder from the left side of the car (behind the LHD driver seat)... Maybe that's an illusion.

At first I wondered if this was a hub bearing gone bad, but it only happens when the trans is under load. Surely a hub bearing wouldn't only make a noise when the car is in gear/clutch engaged? What about a gearbox bearing? OK, so why does the sound seem to come from the left of the car? Why does it not vary with engine or road speed? I then started to think off the wall: there is an air scoop under the car on the left side to duct air up to the remote cooler. Maybe it's the sound of air passing through this? OK, so why does it go away if I dip the clutch pedal and hit the throttle?

I am completely and utterly foxed by this. Any (serious) thoughts on this will be much appreciated.

Here's the video – like I say, you can just hear the sound start at about 20 seconds in...

[Lids]

Its a definite whine, I reckon its a bearing somewhere.

Can't be wind as this would occur at a specific speed.

[deano]

I think your car is haunted....

[Rasser]

Could it be an alternator bearing? 

easy to remove belt and turn alternator by hand, and feel if bearing is bad.

[Black Sheep]

Easy thats the noise a wood slat roof rack makes 

[deano]

Could it be an alternator bearing? 

easy to remove belt and turn alternator by hand, and feel if bearing is bad.

I don't think so. The whine does not follow the engine rpm. But that would be an easy fix (a hellva lot easier than a main shaft bearing).

[Rasser]

Could it be an alternator bearing? 

easy to remove belt and turn alternator by hand, and feel if bearing is bad.

I don't think so. The whine does not follow the engine rpm. But that would be an easy fix (a hellva lot easier than a main shaft bearing).

You are right, it should follow the rpm, if it was the alternator bearing - my bad 
But so should the mainshaft bearing?!   When the whine starts, you could downshift from 4. to 3. and still run car at the same speed. The whine should increase in sound/speed if it was the mainshaft bearing - right?

Actually i changed a mainshaft bearing in my gearbox 5 months ago. I was able to pull it from the housing and the install the new bearing, and this was with only the nosecone dismantled. It was a pain in the ass, but sure was a lot easier to do, than dismantling the whole gearbox. Just wanted to let you guys know that it can be done without complete disassembly of the gearbox.

[Shubee2 (DSK)]

Could Be A Dry Gland nut Bearing it can some times change with movement of the Clutch Pedal also can change if you engine has to much end play  just something to Check

[Fastbrit]

Could Be A Dry Gland nut Bearing it can some times change with movement of the Clutch Pedal also can change if you engine has to much end play  just something to Check

I did wonder about that, too. The end float is OK but it would account for the noise going away with the cluch and hitting the throttle.

[John Rayburn]

Could Be A Dry Gland nut Bearing it can some times change with movement of the Clutch Pedal also can change if you engine has to much end play  just something to Check

I did wonder about that, too. The end float is OK but it would account for the noise going away with the cluch and hitting the throttle.

                                                        Or input shaft bearing.

[lee-maynard]

could it be a loose fan spinning on the shaft

[deano]

could it be a loose fan spinning on the shaft

As in no woodruff key?

[Dan Mazur]

Replace your throw out bearing.

[Donny B.]

As in no woodruff key?

I've had the center bust out of a fan and the fan would speed up and slow down at a different rate from the engine.  You could hear it.  It was held captive by the nut and washers, but it would slip on the the hub.  Either the hole with the flats gets eaten out or the fan can actually break out the center.  I have had both happen, just lucky I guess. 

[Fastbrit]

This is all very interesting, and I thank you for making some well-educated guesses as to what the problem is! The fan and throw-out bearing deals will be easy ones to check as the engine will be coming out in a while so I can cure a leaky crank pulley seal and redo the breather system, although to be honest, I think it is a drivetrain problem. The trans was going to be pulled anyway as it still has a minor side-cover leak, so I may as well get it checked out at the same time. 

[Neil Davies]

This is all very interesting, and I thank you for making some well-educated guesses as to what the problem is! The fan and throw-out bearing deals will be easy ones to check as the engine will be coming out in a while so I can cure a leaky crank pulley seal and redo the breather system, although to be honest, I think it is a drivetrain problem. The trans was going to be pulled anyway as it still has a minor side-cover leak, so I may as well get it checked out at the same time. 

Have you got another complete engine to put in when the motor comes out? Just a 1600 or anything, with a known good alternator etc. That will eliminate the motor side of things if the sound is still there, or confirm it if it goes away.

[Fastbrit]

I'm a one-engine kinda guy... It would be easier to swap the alternator in situ that change the whole engine.  But I am convinced it's drivetrain, not engine-related.

[GreenTom]

similar sound I had when some paper towels went into the fan shroud and stuck into the fan (or licence plate wires sounds similat too). The sound was very very similar but You should be able to se an increase of oil tmep or head temp if You have any of those gauges.
or... it's a small cat or mouse/rat in the fan (whe had lots of cases with old polish cars - FSO polonez or FSM syrena - cats or squirrels ware worming in the engine bays of those cars and when owner started the engine in the mornig... there were a "cat shake" under the hood ) - lots of mess. and similar sound that one on the video afther "HHGGGHHHH" sound

[nicolas]

i would look at the fan as well as it is something that won't effect the driving and is not engine/drivetrain related. maybe the belt makes the sound...
you mentioned endplay was a OK that could have made a noise as well, but different (more familiar in a way).

check the bearings (the big ones) in the sidecovers off the gearbox. as the sound is too low and not following the engine in my opinion or the ones on the axles if they won't have enough oil after 20 minutes off driving.

just guessing with the rest here.

[Neil Davies]

I'm a one-engine kinda guy... It would be easier to swap the alternator in situ that change the whole engine.  But I am convinced it's drivetrain, not engine-related.

I'm sure Matt K would have something - a 1500 single port maybe? Something simple and self contained, bolt in, drive and take out again, just to confirm the gearbox. My dad had a wierd squeal from the front of his Audi - turned out to be the new belt rubbing on the old pulley. Bit of Millers red rubber grease from Frost and the sound went away.

[Fastbrit]

Neil, sorry, but no... 

[.]

Any luck ?
 

[Eric Justus]

I had to stop for a second...b/c when i first watched the video I thought "Oh shit!! The sound is going to be you crashing into that car!!" Oh yeah...u guys drive on the wrong side of the road