intermittant rapid whirring noise whilst driving

[james.ed]

Hi all,

For the last fortnight the moggy has made a short but very noticable whirring/shhing noise (I thought it was static on the radio the first few times) for a period of about five second whilst driving. It seems to come from the engine bay or forward of the driving seat, but its hard to pinpoint as i'm driving. Its only a short noise, like a cam has got free and is spinning wildly, then all back to normal. I won't hear it for another thirty mins then its back and twice in five mins. I don't even know where to start looking - its in gear and the drive is unaffected. I feel no jolts or kick on the clutch or gas. I did think it was happening when I was in gear using it to break on hills, but I can't be sure. I seem to have a very happy engine aside from this.

It doesn't seem to be a problem, but i also have to make a motorway journey west at Christmas and that sounds like the perfect time for it to become an issue!

All help greatfully recieved.

[lambrettalad]

I would try disengaging the clutch next time
is it a squeal?
I seem to remember this sounds like an early sign of the thrust bearings going,I used to call it the budgie noise in my GT6

[james.ed]

Its certainly not a squel.. nothing ear piecing of chalk on balckboard about it. Its closer to the interferance noise on a TV, and not even alarmingly loud! I wouldn't worry but this noise is certainly different to the usual noise. Sorry i can't explaing any clearer. Could this still be the thrust bearings (and what do they do and what happens when they go?!)

[katy]

Possible loose fan belt.

[simmitc]

Seconded. Also check that the nut holding the dynamo pulley is not loose.

[james.ed]

Thanks all - I have checked the belt and it's loose (easily spins without turning anything). I hope this is it! the noise sounds almost like its coming from behind the speedo but i'll change and tighten the belt and see if it fixes the problem. It can't have been causing to many problems and the ignition lights not been glowing.

[MarkyB]

The fan belt shouldn't be rock hard, there should be some play on the longest run, half an inch or a 2 CM from memory.

[rayofleamington]

I was going to say speedo, but you already did!

With the age of our cars it's likely it can be a dry bush. If so, remove speedo, and add a couple of drops of light oil into the edges of the drive (don't flood it!). At the same time, re-grease the speedo drive cable.

Alternatively wait, and if the speedo seizes you'll need a replacement and another cable.

The noise they make when failing is pretty hard to describe, but some kind on "unhappy scraping /whooshy noise" and eventually screechy followed by imminent silence ;-)