Humming Sounds When Going Straight or Turning Left

[eric19371]

Hello all,

Got a weird issue with my wife's S40. There is a humming/droning sound coming from the front when going straight and when you turn left it gets worse. The sound decreases and may actually vanish when turning right.

The turn doesn't have to be anything significant, even the smallest turn of the wheel left does it.

I thought it might be a wheel bearing so I jacked up the car today and tested each wheel in turn and they all seem to turn smoothly without any grinding sound that I understand to be associated with a failing bearing with just a slight rubbing coming from what sounds like the brake pads against the discs. I also checked for movement from top/bottom and left/right.

I had a garage check the bearings only a couple of months ago and they said they were fine then.

All the bushings appear okay (I am not a mechanic but they do not appear broken or cracked) and apart from the gaiter on the left hand side of the steering rack having come disconnected on the side closest to the rack everything else looks okay.

I will get that damaged gaiter on the steering rack looked at but could that cause this noise? The steering fluid reservoir has been on about 3/4 full for as long as I remember so I don't think it is leaking fluid and the steering seems to work fine.

Could it be the tyres? The fronts are fairly new and in good condition, the rears are a few years old but still with about 50% of their tread left.

Any help is much appreciated.

[Leighman]

Mine did that and it was a wheel bearing. Or should I say that when the bearing had been changed the noise went away.

[V8XCV]

Sounds like a wheel bearing failure, you won't necessarily get any wheel movement when jacked up and only takes a few thou of movement to get a noise. It can also cause the the brake disc to rub slightly.

[Danielpsmith]

I had something similar on my c30 I was convinced it was the brakes or a bearing but it turned out to be the top engine mount the one near the timing belt cover, the rubber bush had torn and moved over so when turning it forced metal to metal and made a loud noise I never would of thought to look at it until I found a post on here from years ago, hope you get it sorted.

Daniel

[eric19371]

Many thanks for all your replies.

I took it to my friendly local garage, go the car on the lift and inspected it with one of the mechanics. The bearings and bushings were all checked and confirmed to be in good condition.

They did notice that the front pads and discs needed urgent replacement as the pads had almost gone completely on the inside. I tend to only look at the outside when checking the car and I didn't know they (a) tend to wear more on the inside as that is where the pistons are and (b) were a lot more worn than I thought.

They also noticed that where the disc had worn there was a small rusted lip which is to be expected but this looked like it was rubbing against something, maybe the metal part of the brake pad. This 'could' be responsible for the noise and as the brake pads needed replacing this will be confirmed when done. They will also replace the driveshaft boot at the same time.

I will also get them to check the engine mounts as mentioned by @Danielpsmith at the same time.

[eric19371]

Update: The front brake pads and rotors have been replaced, which did need doing but didn't resolve the issue.

The NSF bearing was then replaced as several mechanics there drove it and they all agreed this is what it sounded like so it was replaced. This didn't resolve the issue but maybe it was a faulty new bearing, so yesterday they replaced it again but the issue is still there.

One possibility they said it could be is the gearbox but as it is quiet when turning right they believe that is unlikely. They also swapped the tyres around to confirm it wasn't them.

The garage owner (a long term acquaintance of mine) said it 'could' be an inner driveshaft bearing so he will try to source one and then he will get it booked in for the fourth time...

[Welton]

What a nightmare! those are the worst kind of troubles where you hope one thing will cure it....then the next....argh!

I've had noisy tyres in the past, usually the budget-end of the market. I'd be tempted to lob the spare wheel on the front(s) to see if that changes the noise.

[FunkyMelon]

Give the brake disc guards a prod and see if the problem gets worse or better.

I've had a noise like this several times and it's always them. They rust and misshape slightly and can rub on each rotation causing a noise similar to what you describe, particularly when turning.

May not be your issue but it's free to find out

[Clan]

Originally Posted by eric19371

Update: The front brake pads and rotors have been replaced, which did need doing but didn't resolve the issue.

The NSF bearing was then replaced as several mechanics there drove it and they all agreed this is what it sounded like so it was replaced. This didn't resolve the issue but maybe it was a faulty new bearing, so yesterday they replaced it again but the issue is still there.

One possibility they said it could be is the gearbox but as it is quiet when turning right they believe that is unlikely. They also swapped the tyres around to confirm it wasn't them.

The garage owner (a long term acquaintance of mine) said it 'could' be an inner driveshaft bearing so he will try to source one and then he will get it booked in for the fourth time...

Get the idiots to change the right hand bearing free of charge ,, have they no experience at all ?
The bearing gets noisier with more load on it and vice versa ! I despair more and more these days with people's incompetence !

[Welton]

Originally Posted by Clan

The bearing gets noisier with more load on it and vice versa

Funny you should say that, our Citroen recently had a front wheel bearing changed - it turned out to be the opposite side of where the noise sounded to be coming from.

One simple proven test is to raise each wheel off the ground and whilst holding onto the road spring with one hand - spin the wheel with the other, you will 100% feel the roughness of the bearing through the spring.

My earlier post assumed all this had been checked