Slow pulsing noise 50-60mph ish (not tyres/brakes)

[No.733]

Hi all. Bit of a puzzler. Car is a 1.6 TDI Greenline III estate, 45,000 miles. I'm getting a slow, low-pitched pulsing noise that I can only hear in 6th gear between about 50mph and 63mph.

 

Logically it can't be tyres or brakes as the frequency of the pulsing, which is maybe more a vibration than a noise, is quite slow. It's less than a pulse per second. The best way I can describe it is that it's like an old-fashioned nuclear power plant sound effect, like a "whumm... whumm... whumm". 

 

I've Googled and searched and asked around, but I can't fathom this one. Has anyone else had anything like this, and how did you cure it? 

[Stewart7]

Do you have odd tyres on the front?  It could be the the front axles revolving at slightly different speeds causing the differential gears to revolve more than usual.

[No.733]

2 hours ago, Stewart7 said:

Do you have odd tyres on the front?  It could be the the front axles revolving at slightly different speeds causing the differential gears to revolve more than usual.

Thanks, but no; evenly-worn Michelins all around. 

[ords]

briskoda.net/forums/topic/461296-humming-noise-at-60mph/?tab=comments#comment-5177209

[TomTewkesbury]

Hi this sounds exactly like the sound I was getting (although it was only at 70+) when I bought my second hand vRS earlier this year from a dealer. 

 

It turns out that it was the front wheel bearing so I'd suggest that gets checked first. 

 

It didn't make sense that it could be that because it was a slow deep rhythmic pulse but they replaced the bearing under warranty and that completely fixed it. 

 

 

[Rustynuts]

Swap wheels front to back first, free diagnosis / fix if it's a tyre going out of shape.

[KenONeill]

I'd agree that the most likely causes are tyre out of round or worn wheel bearing.

[Gmac983]

Are the tyres well down near the legal limit? As there would be less "give" in the worn tread blocks compared to a new tyre. This can give a resonating sound on certain road surfaces. Otherwise I agree as above, could be any of the wheel bearings. Also a deformed tyre would likely give some sort of shake in the car whilst driving. 

[No.733]

Thanks for the replies, but the noise totally disappears when I dip the clutch, so surely it can't be a wheel bearing?

[gregoir]

You said "in 6th gear". Now you tell us the noise goes away when you press the clutch pedal. So the engine is at idle and  you are coasting  along, with the gear lever still in the 6th gear position, when the noise goes away?

That sounds like a drive train problem, rather than tyres or wheel bearings. 

Edited 17 September, 2019 by gregoir

[SuperbTWM]

If the noise goes away when you dip the clutch but you still have it in gear it has to be the engine or flywheel as the gearbox and drive train will still be turning.

Edited 17 September, 2019 by SuperbTWM

[No.733]

23 hours ago, gregoir said:

You said "in 6th gear". Now you tell us the noise goes away when you press the clutch pedal. So the engine is at idle and  you are coasting  along, with the gear lever still in the 6th gear position, when the noise goes away?

That sounds like a drive train problem, rather than tyres or wheel bearings. 

This is what I'm worried about... 

[Rkdee]

Any result on this?

[Sava159]

On 15/09/2019 at 12:00, TomTewkesbury said:

Hi this sounds exactly like the sound I was getting (although it was only at 70+) when I bought my second hand vRS earlier this year from a dealer. 

 

It turns out that it was the front wheel bearing so I'd suggest that gets checked first. 

 

It didn't make sense that it could be that because it was a slow deep rhythmic pulse but they replaced the bearing under warranty and that completely fixed it. 

 

 

Do you know on what side it was? I also get that sound only on 110-120kmh, and it doesnt matter if it is on 5th, 6th or N. The sound remains there..

[TomTewkesbury]

3 minutes ago, Sava159 said:

Do you know on what side it was? I also get that sound only on 110-120kmh, and it doesnt matter if it is on 5th, 6th or N. The sound remains there..

Hi. It was the front left wheel, if that's what you mean