Odd noise when accelerator released

John L

John L

A2OC Donor
Today I have been having one or two odd issues with my A2 (1.2tdi).
When I exceed 60mph (well from around 96km/h) there was noticeable vibration coming back through the steering wheel. The vibration seems to be coming from the front left wheel.
The tyre looks normal and has good tread and no visible damage. I will take it off soon to check if the balance weights have fallen off or if there is any damage to the inside of the tyre.

Later on during the drive I also started to get a whining noise when the accelerator is released but the car is in drive. I put the car in N on a downhill section and the whining disappeared and then started again when drive was engaged.
The noise disappears when the accelerator is pressed down.

Under breaking the noise disappears and starts again when the brake is released.

The noise varies in intensity but turning seems to make no difference. Also as the noise does not increase with speed and disappears in N I suspect it is not the wheel bearing (I think that the bearing was replaced less than 2 years ago anyhow). I also stopped and jacked up the front wheel and found no side to side movement in it.

The sound occurs with varying intensities in all gears. Also when reversing the car seemed a bit lumpy just as it starts off with the problem seeming to come from the front left wheel.

I have some videos that will hopefully have the sound if needed.

Does anyone know where to start looking/have any ideas about what it could be?


John
 
I guess the problem could be one of the CV joints?
There were notes when they the dealer looked at the gearbox that there was some "sweating" somewhere in the drive and so I guess I'll start looking there.

Does this make any sense as the noise disappears when the accelerator is pressed or when the car is freewheeling?

I am slightly confused as to what exactly would cause the noise when the gears are engaged but the accelerator is not.
The speed seems variable.

The vibration could be related but only kicks in at higher speeds.

John
 
John L said:
I guess the problem could be one of the CV joints?
There were notes when they the dealer looked at the gearbox that there was some "sweating" somewhere in the drive and so I guess I'll start looking there.

Does this make any sense as the noise disappears when the accelerator is pressed or when the car is freewheeling?

I am slightly confused as to what exactly would cause the noise when the gears are engaged but the accelerator is not.
The speed seems variable.

The vibration could be related but only kicks in at higher speeds.

John
Click to expand...

My Money would be on a buckled wheel causing the vibration, check out the inside rim of the wheel for damage,

As for the noise, I am not familiar with the 1.2 tdi, but it sounds a little like a diff noise perhaps?

Steve B
 
I guess it could be diff noise.
It seemed louder in the cabin than outside. Wouldn't the diff make more noise when you put power through it?
The noise seemed to come from the front left corner rather than from the centre (but I guess the gearbox is on the left hand side...)

Could a buckled wheel be causing the differing wheel speeds and leading to noise from the differential?

With the vibration I released my grip on the wheel and did not notice the car pulling to the side.

I guess it would probably be good to put the car up on axle stands and turn everything by hand and see if there is any clicking or unusual sounds.

Is it worth swapping the front wheels from left to right and seeing if the noise and vibration change side (if a visual inspection finds no obvious fault with the wheel)?

John
 
John L said:
I guess it could be diff noise.
It seemed louder in the cabin than outside. Wouldn't the diff make more noise when you put power through it?
Not necessarily, under load (i.e. when accelerating or decelerating), all slack is taken up and no slack can sometimes mean no noise.
On the overrun (i.e. when decelerating or just cruising, the teeth on the diff can float around more and therefore cause noise.
I am not saying that this is the case, I am just saying that it might be.
The noise seemed to come from the front left corner rather than from the centre (but I guess the gearbox is on the left hand side...)

Could a buckled wheel be causing the differing wheel speeds and leading to noise from the differential?
Highly unlikely, the bucking cannot affect wheel speeds at all. But it could be a badly worn driveshaft? That would give noise and vibration? But I still think it is more likely to be a buckled wheel.

With the vibration I released my grip on the wheel and did not notice the car pulling to the side.
A Buckled wheel would not cause the car to pull to one side or the other.

I guess it would probably be good to put the car up on axle stands and turn everything by hand and see if there is any clicking or unusual sounds.
Yes, grab the wheel and turn it left and right quickly (like you are turning a steering wheel, any noise or clunks would indicate a problem

Is it worth swapping the front wheels from left to right and seeing if the noise and vibration change side (if a visual inspection finds no obvious fault with the wheel)?
You can try that, but swapping the front to the back would be more noticeable, a buckle on the rear wheel is much less noticeable. So if the vibrations reduce after the swap then you have the cause, a damaged wheel (although while swapping it, you are likely to notice the damage anyway!)

John
Click to expand...

Hi John,

Some comments above

Steve B
 
Thanks for the advice Steve!
There was apparently some joint "sweating" somewhere.
I'll try and find out where this was as it may be linked.

John
 
The wheel looks ok but is missing a weight. I guess this would explain the vibration. I'll take it into a tyre shop and have it rebalanced and see if they notice any warping or anything more sinister.
Now it is just the noise to solve!
 
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