I am a new member. My name is Dave. I joined so that I might get some guidance on an issue. I have with a brand new 2017 XJR Sport. I bought it a few months ago with 15 miles on the clock. After a day of driving I noticed a subtle but annoying humming sound. It starts at very low speeds around 12 MPH and comes and goes depending on the road surface and at all speeds. It is there at all speeds although it can be quieter or louder at times. It fills the whole passenger area and there is no distinct location of its source. It sounds the same from the drivers seat or the passenger seat or the back seat....same sound same loudness. The dealer has had the car for 20 days trying to locate it. They have changed the wheels and tires. That made no difference. Used chassis ears all with no luck. If I drive over a expansion joints on a bridge, the humming changes pitch as the front and rear wheels pass over the bump. The pitch of the sound changes with both the front and rear wheels going over the bump.The humming is there even if I put the vehicle into neutral and coast. Braking makes no difference either. The dealer has checked the prop shaft bushing, brake pads cooling fans and anything that may be loose on the car.

I do have a video with the sound on Youtube but did not know it it was ok to post here.

I have owned several Jaguars and have never heard a sound like this. It is NOT a mechanical sound. it is more like a harmonic sound. Sorta like the sounds from a freezer fan motor electrical hum.

Any ideas would be greatly appreciated.

 

Welcome to the forum Dave,

I've copied the post from your Intro thread fro advice from members with the same car.

You can post a link to your YouTube video here.

Graham

 

Here is the Youtube video. The sounds is subtle and can best be heard near the end of the clip. It is is a hum. Much like if you simply close your mouth and hum to yourself. That is whatit sounds like.

 

im not able to listen to the video at the moment, but i know jaguar uses annoying interior climate sensors that make an annoying constant buzzing/humming sound.

could this be it?

 

Yes, it could be. I will check further into that.
What throws me is it changes pitch. That change in pitch happens with both the front and rear tires going over bumps. Also, It does it with the Heating and Cooling systems shut down.
The only thing that plays into all this is the suspension. I don't know how the air suspension system works on this vehicle. If is uses electrics to adjust it or not. But that is the area I suspect. The dealer bet me off on that.

I will take the car out again, and pay more attention to the climate controls. You may have a point.

Thank you so much for helping me this.

 

When they changed the tires and wheels are the tires the same brand? Does it sound different over different road surfaces?

 

Thank you for the reply. The tires and wheels were swapped temporarily off a used 2017 XJR. They were not the same brand. Mine are I want to say Nitro? The hum was exactly as it was with my OEM tires and wheels. The hum gets louder over rougher road. But, if the road is extremely rough, the road noise itself drowns out the humming noise. Over very smooth roads, the hum is still there but not as loud.
The hum is not in your face. It is like a background noise that can be drowned out by a radio or climate control if it is turned up high.
It sounds exactly like you might sound if you closed your mouth and hummed to yourself.
If you hit a bump, with any wheel the pitch of the hum changes for a second.
It does it in neutral whilst coasting.
It does at at 12 MPH all the way up o freeway speeds and over..
Thank you for your help. It is truly appreciated.

 

There is a correction to my comment about the tires that are my XJ. They are Zero Nero tires. Not Nitro...

 

My XJ has some of this background sound and it is somewhat dependent on the road surface but I do not notice it as I listen to the audio system all the time. If you are looking for silence I'm not sure if you will get it. Have you driven other XJs? The SuperSports, XJRs, and R Sports are tuned for performance handling and this may be a factor.

 

JozJag, the air ride part of your suspension is only on the rear suspension. In short, you have an "air coil" (think air bag, but not quite) that will adjust the pressure inside the coil to maintain the rear of the car at a constant height. There are sensors that look at the rear height and will do what it takes to make it stay at some pre-programmed height. The rest of the car has special shocks that have an adjustable orifice in them. Depending on how far open or shut this valve is, depends on how fast the fluid can move inside the shock. This valve fails in the shut direction which will result in maximum dampening (ie, harshest/firmest ride). As the valve opens, the fluid can move easier and therefore the ride will soften up.

Listening to the sound, it would appear to be around 500 Hz or something in that range. I mention this as that is also the same frequency at which the suspension system operates at. If you were to have a shock that is failing that is someone transmitting the sound of this valve to the body of the car, that would make it appear to be coming from all portions of the car (it is shaking the body of the car). The issue I see with this is that valve is fairly small and for it to shake hard enough to transmit through the body of the car would have to be a pretty serious thing. Something you can try is when you are having this sound occur, shift the suspension into "Dynamic Mode" and this will cause the valves in each shock to essentially turn off, giving you the stiffer suspension. If you sound goes away, then this confirms that you have something going on with the shocks in the car.

 

To expand on why I am leaning this way is that the car looks at the road conditions (ie, how much the shocks are having to do work) and adjusts the shocks to maximize ride comfort. This would help explain why on some road surfaces the noise goes away and while on others it is there. There is a lot more that feeds into this system to set the setting of the shocks (ie, yaw of the car, movement of each wheel, G's seen on the body, steering wheel position, etc).

 

 

Any difference with climate control on/off? Trying to eliminate compressor.

 

 

This morning I did take the X351 out to test for using dynamic vs not using it to see if that affected the humming sound. Two things, In short no it does NOT. What caught me by surprise was dynamic mode is by default ON. On uses the switch to turn it off.
Is that right?

While we are at it. Am I correct in thinking dynamic mode os more about suspension whilst winter mode is more about braking?

 

Maybe a motor mount or transmission mount problem?


Get up to speed with it making noise and shift into neutral and coast.
After that put it in neutral and turn the engine off and coast. Note this will kill the power steering to so do it out away from things on a straight road!
.
.
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Clubairth1; Yes, I did that. Keep in mind that one can not shut off the motor whilst moving. I can and did put it into neutral and coasted. I started the neutral coast at 60MPH and coasted all the way down to a stop. At about 12 miles per hour, the humming went away. it never changes in tone. Nothing changes at all. I physically check all the mounts and all are tighter than a .....well... they are very tight. LOL There is no hum at idle or till about 12mph.

This is hum is not as quiet as it is on the video. It can get very loud over the right road surface. It does not vary with speed but does jump up in pitch over certain bumps for a fraction of a second as a wheel or wheels hit that bump.

If I had hair, I would be pulling it out.

 

JozJag, I don't know about the XJR specifically, but my Base XJ has the suspension in "Normal" mode when you start it (ie, best ride that the computer can figure out). When you put the car into dynamic mode, it pretty much turns off the dampening and gives you maximum dampening (ie, stiff suspension).

As for what winter mode does, it does a few things. The big one is that it will start the car out in second gear vice first. What this does is it limits the amount of torque that you can make, therefore minimizing the chance that you are going to have wheel slippage. The second thing it does is automatically engage the brakes lightly to help control wheel slip. The last thing it does is slows down the response of the gas pedal. You can stomp on the gas pedal, but the throttle body is going to open slower, allowing for a more gradual application of power. Dynamic mode simply stiffens up the suspension to allow for more spirited driving.

 

Thermo I believe that JaxJag has the model XJ R-Sport that is similar to the XJ R-Sport that was available in some previous XJ incarnations, i.e. base XJ standard wheelbase with XJR bodywork and in x351 has a V6 engine.

 

XJsss I believe you are correct