Hi all, I’m new to the group so not quite sure how this works but I’ve been to about three garages who’ve all said they’ll have to charge a full days labour to try and find out what this sound is and even then they might not found it, I’ve been told to ignore it until it’s really bad but it’s bugging me. This is a medium to high pitched humming noise coming from driver side best heard when engine is stationary or below 20mph, and when inside cabin with all windows heard. Can be heard when bonnet is up but not as loud as when you are inside cabin.
 

I thought maybe it was a bad fuel pump because the car has stuttering starts and has lost some power in accelerating but mechanics ruled that out because the fuel pump is in the rear of the car this is coming from the driver side and can be heard the most when inside cabin with windows shut.

I recently changed my drive belt but did not change my water pump, however I’m not sure if a bad water pump would make a noise such as this?

does any have any ideas please?? I’ve been struggling to diagnose this for 6 months!! 
I have a MK7 Fiesta on an 58 plate running 119,000 miles on petrol.

Could well be the water pump, at that mileage should have been changed at the same time as the belt.

21 hours ago, eddie eastwood said:

Could well be the water pump, at that mileage should have been changed at the same time as the belt.

That’s exactly what a different mechanic said, the mechanic who fitted the belt mentioned nothing of the water pump😡 thanks so much!

If it's been the same for 6 months it can't be anything major.

Which belt was changed?  If just a drivebelt (aux belt) then water pump wouldn't usually be changed with that.  If it was the cambelt (timing belt) then the waterpump is generally worth doing at the same time - and will be overdue if not done at that age and mileage.

32 minutes ago, TomsFocus said:

If it's been the same for 6 months it can't be anything major.

Which belt was changed?  If just a drivebelt (aux belt) then water pump wouldn't usually be changed with that.  If it was the cambelt (timing belt) then the waterpump is generally worth doing at the same time - and will be overdue if not done at that age and mileage.

This has crossed my mind and I would ignore it only for the fact that is slowly has been getting worse, whereas 6 months ago the sound was very quiet and not often but now often and loud. Don’t want my engine to be too damaged, I’m still planning on keeping the car running for a few years.
I’m sure it was a drive belt, or serpentine belt, bought for £34 from Ford, and cheap on labour. I thought that was cause of noise as when I listen close under bonnet it sounded very close to the serpentine belt, but alas the noise continued once changed. Could be pullys or alternator maybe? Nightmare to diagnose...

7 minutes ago, Becky Garside said:

This has crossed my mind and I would ignore it only for the fact that is slowly has been getting worse, whereas 6 months ago the sound was very quiet and not often but now often and loud. Don’t want my engine to be too damaged, I’m still planning on keeping the car running for a few years.
I’m sure it was a drive belt, or serpentine belt, bought for £34 from Ford, and cheap on labour. I thought that was cause of noise as when I listen close under bonnet it sounded very close to the serpentine belt, but alas the noise continued once changed. Could be pullys or alternator maybe? Nightmare to diagnose...

Have you got any history of the cambelt having been changed?  If not, that's well overdue and would recommend it asap.  Waterpump can be changed at the same time.  It won't be cheap but if the cambelt snaps then it's game over for the engine.