Technical Mk 2 2004 Punto whining noise

[CJS]

I've got an odd whining noise on my Mk2 2004 punto (1.2 8v active), coming from the engine when the car is moving at 40 mph or more. It's intermittant but getting more frequent. It will suddenly start for no obviouse reason, e.g, cruising at 50 on a flat road, no accelleration etc. and will either end quickly or fade away slowly.
The pitch of the sound is in tune with the road speed rather than the engine speed - if I put the clutch in and give it revs the pitch doesn't change. The sound generally stops after slowing below 20ish and has never appeared while the car has been still.
If I stop quickly and listen to the pitch change it does sound like something spinning to a stop so I'm wondering it it could be the radiator fan. Had someone in the car with me today and he thought it might be the fan bearing going dodgy and the sound being caused by the fan being spun by air blowing through the radiator while the car was moving. Does this sound likely? I can probably cure it by disconnecting the fan temporarily, taping it to stop it spinning and test driving, just wondered if anyone had experienced anything similar.

Cheers

 

[NumanR]

Have had this problem many times on Punto, you have hit the nail on the head, an easy way I have found of proving this is either tape the fan down temporarily, or my favourite when testing with customers is to get the car to do it on a dual carriageway and then pull in behind a lorry. The lack of airflow reduces the spinning of the fan and this causes the noise to stop. Then pulling out into the airflow causes the fan to start spinning again and the noise returns. The noise can also be simulated by spinning the fan manually (ignition off) and occasionally you will here a very rough sound and you can sometimes feel the rear bearing being rough.

 

[CJS]

Thanks NumanR, never would have thought of the trick with the lorries, I'll try that tomorrow.

Can the bearing be greased or is this likely to be a replacement job?

Cheers

 

[NumanR]

No they are not serviceable, you could try and spray a little wd40 and hope it can work its way into the rear bearing but I dont think it will make much difference. Good luck

 

[JackFi]

Thanks NumanR, never would have thought of the trick with the lorries, I'll try that tomorrow.

Can the bearing be greased or is this likely to be a replacement job?

Cheers

I had the same thing go wrong on my punto wd40 will most likey do nothing. i would just get it replaced. i brought a new fan for around £50 - £60 and fitted it myself

 

[Homi]

yep sounds like the bearing had the same prob about a week ago, you could try copper grease or a bit of wd40 but i doubt it will help (it didnt for me) if it is the bearing the fan motor will need replacing they arent that much i got mine done for about £50, hope this helps