Strange noise

[Newbie777]

Hello, 

When I park up after a short or long drive and put the car in Park, I hear a faint humming/vibrating noise from the engine, it lasts about 30 secs to 1 minutes and goes away and does not come back.

Is it normal?

There are no error lights or leaks.

[Malc1]

Some electronic wizadry finishing off its circuit training and winding down maybe 🤔

Malc

[NemesisUK]

Brake pressure pump topping up the reservoir?

[DomTurner]

If you have air suspension then it could be the compressor kicking in? When parking up or stopping after driving at higher speeds I can hear and feel mine kick in for about 20-30 seconds to raise the car up.

 

You could try manually changing the cars height and listen out for the same noise.

[Newbie777]

28 minutes ago, Malc1 said:

Some electronic wizadry finishing off its circuit training and winding down maybe 🤔

Malc

Sounds about right, nothing surprises me with this car.

[Newbie777]

15 minutes ago, NemesisUK said:

Brake pressure pump topping up the reservoir?

Not sure, is this normal?

[Newbie777]

13 minutes ago, DomTurner said:

If you have air suspension then it could be the compressor kicking in? When parking up or stopping after driving at higher speeds I can hear and feel mine kick in for about 20-30 seconds to raise the car up.

Yes it has air suspension, like I said don't hear it when am driving, but when stationary and parked up.

[NemesisUK]

Just now, Newbie777 said:

Not sure, is this normal?

Yes, at least on my RC and RX but must admit 30sec to a minute seems a long time. I tend to hear it only for approx 5sec

[NemesisUK]

Just now, Newbie777 said:

Yes it has air suspension, like I said don't hear it when am driving, but when stationary and parked up.

My Mercedes levelled up on parking, particularly noticeable if the ground was uneven

[Newbie777]

11 minutes ago, NemesisUK said:

Yes, at least on my RC and RX but must admit 30sec to a minute seems a long time. I tend to hear it only for approx 5sec

OK will do some more investigating with times and type of sound.

So far sounds like compressor as my drive has a slight incline  so when I park up it could be this.

[Newbie777]

12 minutes ago, NemesisUK said:

My Mercedes levelled up on parking, particularly noticeable if the ground was uneven

Thank you that helps

[Spock66]

Do you get a similar noise if you just unlock the car and open a door?

I believe this is the electronic braking system as you don't have conventional vacuum servo assistance with a hybrid.

[Newbie777]

2 hours ago, Spock66 said:

Do you get a similar noise if you just unlock the car and open a door?

I believe this is the electronic braking system as you don't have conventional vacuum servo assistance with a hybrid.

Am not sure, further investigation needed. i usually select brake hold when I drive? 

I drove a mile or so now, 20 min wait in shop and drove back and did not hear anything  when parked up.

Will check when driven a bit, open the door etc

 

[Newbie777]

On 12/20/2023 at 6:55 PM, Newbie777 said:

Am not sure, further investigation needed. i usually select brake hold when I drive? 

I drove a mile or so now, 20 min wait in shop and drove back and did not hear anything  when parked up.

Will check when driven a bit, open the door etc

 

An update, 

Have not heard the noise yet for a few days, cannot hear whenopnen the door etc.

Can't be the parking brake as the sound  comes from the front.

So will come back when it happens again

 

[DomTurner]

2 minutes ago, Newbie777 said:

Have not heard the noise yet for a few days

Did you try manually adjusting the height of the air suspension, just to rule it out? You should have a button near the gear selector that says something like "Height - High" and should run the air compressor for around 30 seconds to raise the car a little bit.

[Newbie777]

9 minutes ago, DomTurner said:

Did you try manually adjusting the height of the air suspension, just to rule it out? You should have a button near the gear selector that says something like "Height - High" and should run the air compressor for around 30 seconds to raise the car a little bit.

Good idea thanks, I will raise the height 

[Newbie777]

19 minutes ago, DomTurner said:

Did you try manually adjusting the height of the air suspension, just to rule it out? You should have a button near the gear selector that says something like "Height - High" and should run the air compressor for around 30 seconds to raise the car a little bit.

Hello DomTurner,

Great news..

You are right it is the compressor,made that sound for about 30 seconds and the height light came on and it raise the suspension a little bit.

So is that right that when I park on my drive slightly uphill the compressor will come on now and then?

[DomTurner]

Glad we figured it out! 

Just now, Newbie777 said:

So is that right that when I park on my drive slightly uphill the compressor will come on now and then?

That is correct. Usually once I have parked the compressor will kick in after about 10 seconds, I then wait for it to stop before switching the car off just so it is level.

You may also notice it after coming to a stop after travelling at high speeds. This is because the car will lower itself down to improve fuel economy above 60mph I believe.

If you can feel the compressor kick in through the footwell area, the mounts may need replacing on the air compressor - I have left mine at the moment as I don't really mind the noise/vibration.

[Newbie777]

3 minutes ago, DomTurner said:

Glad we figured it out! 

That is correct. Usually once I have parked the compressor will kick in after about 10 seconds, I then wait for it to stop before switching the car off just so it is level.

You may also notice it after coming to a stop after travelling at high speeds. This is because the car will lower itself down to improve fuel economy above 60mph I believe.

If you can feel the compressor kick in through the footwell area, the mounts may need replacing on the air compressor - I have left mine at the moment as I don't really mind the noise/vibration.

Brilliant thank you very much, the noise is more in the engine bay than near the footwells, but am glad it's all normal, relief, one less worry,

Thanks again, really appreciate your advice.