Vauxhall Corsa - Whirring noise?

Miseryschild

Ok, i'll give as much info as I can to see if anyone can help us.

We have a vauxhall corsa (N reg i think - will check when i get up) and every now and again there will be a whirring noise coming from either the engine compartment or behind the dashboard.

Now the problem is we can not check it when its stood still mainly because:

1. The whirring noise starts at various speeds - normally starts at around 70mph but it will end up starting at around 30mph
2. As you decrease speed it will wind down and disappear until you accelerate above said speed again then it reappears.

Now originally we thought it was the water pump as it sounds like its coming from the engine and it wasnt the altenator as the battery held its charge but after changing it it was still there.

Anyone have ANY idea what it could be? It doesn't affect the control of the car, it drives and handles normally while the noise is happening, it is just getting very annoying. I want to check behind the dashboard but unfortunatly I can't as the car is needed for work 6 days a week.

Thanks in advance
~MC

goldspanners

could be a wheel bearing?

anewman

Jack up each wheel and spin as fast as you can, do rears with handbrake off and in first gear, and fronts with handbrake on neutral. Listen closely for any sound from the centre of the wheel. Also grab the wheel at 9 and 3 o clock and try rock the wheel side to side, and same for 12 and 6 o clock to see if there is any "play" in the bearing.

Even though it sounds like it's coming from the front it could still be a rear one as wheel bearing noise is rather difficult to determine where it comes from.

Miseryschild

AFAIK it isn't - the steering is fine - had it in a garage (family friend so is v. trustworthy) and he has no idea what it could be. Like I said it doesn't affect the control of the car - its just a noise that appears at a certain speed but will go when you slow down enough.

~MC

EDIT - anewman - will try and do that tomorrow if i get a chance. thanks for that info - will update when i've checked.

Pew_Pew_Pew_Lasers!

Personally I'd find a quiet stretch of road and turn the engine off once up to speed, to isolate engine/mechanical.

Don't do this if you don't know what you're doing though.

anewman

Easiest way to eliminate it is to dip the clutch and foot off gas. The sound will remain constant if wheel bearing changing only with car speed as it slows.

oldagetraveller

Speedometer cable?

Miseryschild

anewman/goldspanners - isnt wheel bearing. there is no vibrations on the steering wheel and all the wheels dont have any weird sounds.

pew pew - dont think that would do anything as it isnt from the wheels from what i can tell

oldagetraveller - doubt it - the speedometer is fine, it only happens intermittently. doesnt always happen. sometimes the car can drive for miles without it coming in but could start just like that for no reason.

Thanks for all your help. Im having a feeling its the heating fan behind the dash but cant check as need the car 6 days a week

~MC

anewman

Miseryschild wrote: »

anewman/goldspanners - isnt wheel bearing. there is no vibrations on the steering wheel and all the wheels dont have any weird sounds.

If was bearings, wouldn't necessarily result in vibrations on steering wheel. But the sound would be persistent and occur on all trips when getting up to speed.

vikingaero

Could be your ventilation fan being forced to spin with air pressure as you speed up. Try turning the air direction to the footwell and close all airvents.

Miseryschild

anewman - didnt think of that. but it is only at random times, not all the times.

vikingaero - will try that - just got to wait to see if itll do it again. only happens at random times.

~MC