Humming from passenger side wheel when turning right, that stops when brake touched

[ThomasG]

If I drive for a while - home to Glasgow (100 miles) or two days ago, home to Melrose (35 miles), I notice a humming or low woo sound (sorry no recording), from the passenger wheel area when turning right or driving along a road that goes even slightly right.

It stops when I touch the brake pedal.

It is definitely something in motion that is making the noise. 

This time, when I was on a road that was going slightly right, it also came on with a pulsing hum.

Any ideas? It's going to the local garage when there is a space - hopefully to go on a lift and get an inspection - but I thought I'd ask the hive mind first...mainly to get an idae of what is might be and get ready for cost!

[Magnet]

Hello Thomas, 

Thanks for being in touch.

Sounds typical of near side wheel bearing issue.

Kind regards,

Gareth. 

[ThomasG]

I've had bearing replaced, but mechanic says he doesn't know if it's fixed. He thinks he heard it again on a test run. I haven't heard it, though granted I've not driven much. So it's a waiting game. A £149 waiting game ! 🙂

[Stevey Y]

Hi Thomas, could it be the backplate rubbing a little where he wrestled with the hub during the bearing change, done that one a few times and then had to crawl under the car to pull it back a bit further which normally cured the problem.

Regards Steve.

[ThomasG]

Update...

From speaking to a mechanic friend up in Glasgow, he wagers, though cannot check until it's up on a lift, that it's the caliper.

He says he had a very similar experience with an A4. Although counter-intuitive, it ended up being the caliper.

We've worked though everything and Occam's Razor...it seems to be the cause:

1. Intermittent juddering when braking (from front left wheel)
2. This was happening last year, and went when new disks/shoes were fitted. (same side)
3. Owl-like long hoot/howl from same wheel when driving slowly, goes when you just touch the brake as softly as possible.

It all makes some sense, as the noise is definitely a resonation.

Now, I would have thought the mechanic who did the front disks would have looked at the caliper, but...

So, advice here from members is - new calipers or rebuild kit. And if new calipers - I was looking at TRW.

T

 

[Stevey Y]

Hi Thomas, I really would not be buying a refurb kit unless you are bored and own a compressor to blow the calliper piston out, have found through experience that once the piston is out the calliper bore is corroded along with the piston and scrap basically.

This would have been a long term problem from what I can conclude, first the warped disc and then the wheel bearing, and now it sounds as though the disc is beginning to warp again, I would try this first before I ran off and bought new front calipers, I had the same problem with one of my cabs it started with a shudder on the n/s front when braking so I changed both sides discs and pads this was fine for a couple of weeks until it started again, took the offending disc back they changed it and I refitted it, another two weeks I am back to square one but this time I have a rumbling wheel bearing as well.

changed the discs pads and bearing, [the car is doing a thousand miles a week as a cab] two weeks later back to the same thing by now I am beside myself, so going back to basics if you work out all dual circuit brake systems are diagonally opposed so the n/s front and o/s rear brakes form a circuit this counters any catastrophic failure of the other circuit through total fluid loss from the reservoir, therefore the vehicle will stop with a level trajectory, in my case the o/s rear caliper was just holding on slightly just enough to prevent the brake fluid pressure to dissipate from the front n/s caliper, when all the parts are new the front discs and pads will suffer this anomaly until you drive a good distance because of the closer proximity of the pads when the disc expands the pads will drag albeit a tiny bit this then causes friction which heats the disc even more than normal then the hub and bearing become part of the heat sink and it boils the grease out of the bearing.

A good way to test this is leave home slowly with minimum braking, find a nice bit of straight road drive for at least two miles with minimal use of the brakes then stop for ten minutes, get out of the car and touch the surface of the o/s disc gently it should be warm not red hot if you go to the n/s and it very hot that will be the problem.

Steve.

[ThomasG]

Hi Steve,

I shall try that in the morning. Obviously, not many miles done in the last 12 months, so to have a warped disk is alarming to say the least. I have put my hand near both wheels after a drive, and nothing untoward heatwise, and it doesn't judder all the time - that's why I thought stuck pistons...

However, I'll get back once I've tried your suggestion tomorrow.

Thanks

 

[Stevey Y]

Hi Thomas, I forgot to mention another sign of what I posted was a slight blue tinge on the middle of the offending disc, either way trial of the method described will at least rule out that problem, if it is the caliper TRW are a really good make.

Steve.

[ThomasG]

OK - drove for 4 miles and stopped. No heat at all on the disks. Continued to drive to Kelso, no problems - no judder on braking. All seemed fine.

Came back on more windy roads, brakes still ok - maybe I could feel something through the pedal, and then the howl came - though it's not a howl -it is like a very loud and long owl hoot. We tried to record it, but it's resonating through the car body and difficult to capture - though when she put her window down (we were in a v under an old railway, you could hear it outside. Then it went. It only occurs under 20 miles an hour.

When I got home - both disks were hot, as expected. There does seem to be more dust on the wheel on the passenger side one, and there are noticable lines on the disk. They weren't cheap disks...

I am going to have to keep on at my mechanic until he can get it on the lift, he's snowed under...

Will advise as I want to be able to drive a long distance when lockdown ends!

[ThomasG]

It gets better...

Looking at my tyres I noticed more wear on the outside of the passenger side wheel - enough to get me a warning from the local constabulary, should I be stopped. So, I knew new tyres were due this year, I forked out on a full set of Michelin's (more later). While in the tyre depot, the owner checked out the bearing, and the caliper for play, he gave the whole thing a blast from the compressor too. No play on bearing, no tell-tale marks on the disk, no play in half-shaft - that he could see or feel.

New wheels on - drive home - c.20 miles. Decide to brake a lot and take corners 'well'. Then slowed down to 20 in the villages (it's the new speed limit in Borders - the Audi hates it!) and NO howl - 20 was the speed it usually kicked in at. To double check, I drove into England...to Berwick for my shopping. No howl in the town.

There is still a judder on braking though, so it was agreed by pal in Glasgow and at the tyre depot, that it could be uneven wear on the pads - the wheel alignment was out, and it's all corrected now. So we shall see. A set of pads is a lot cheaper than a caliper.

The tyres - I know I asked ages ago. I have Pirelli on when I got the car - but these Michelin Pilot Sport are excellent for noise and grip. Mainly a summer tyre it seems, but so far so good.

Let's wait and see if it's the pads then!

[Stevey Y]

Hi Thomas I would pay good money to see a video of you doing a Walter Rohle impression, nothing wrong with growing a tail and a pair of horns for half an hour, I hope it is the pads, as you say its the cheaper option I have had pads wear unevenly if I do loads of town work and it seemed to get worse with the abolition of asbestos this anomaly was explained to me by a Lucas brake technician at the NEC in Birmingham a few years ago, as he explained the new lining materials had a propensity to glaze and deform when used gently and worse than that because they use a higher thermal efficiency rating if you sit with your foot on the brake while at traffic lights the heat they have accumulated goes back in the disc and eventually warps it by causing localised hot spots.

Steve.