Hello All,

I am new to the forum & looking for some guidance on what i have discovered on my 04 XJ8. I recently did the brakes on my car & didn't think i would have any problems with suspension but i do!

i dont have a lift so i lifted each corner & did them all separately, they all let the air out automatically as i lifted each corner.

My problem happened after i did the left rear side as i let it back down and started the vehicle to get the ride height back it would make this whining noise, almost like a light whistle and would let maybe 10-15% of the air out and will not stay at the top of the ride height like the other 3 corners.

What i notice is that the ride height in the rear left will adjust everyday like normal but when it gets to the top level its almost like it cant hold it at the proper ride height it needs to be and lowers about half an inch followed by the annoying whining noise.

i tried putting it in neutral and letting it adjust only for the same thing to happen over & over again. as soon as it hits the proper ride height (last 10-15% of inflation)

I have no CEL or any notices on my dash of anything. iv included pictures of what the heigh looks like parked. hopefully someone can gie me some insight on what it can be or why its doing this & how to fix it besides replacing the air shock!

 

Odd that you have no fault message displayed. Have you tried driving slowly round the block, as sometimes this fixes the problem ? It fixes it as the system now knows the car is back on the road and moving. However, if this doesn't work there may be something failed or damaged.


A clue would seem to be the fact you recently did some rear brakes work. You may have displaced or damaged one or both of the rear suspension height transmitters. The air suspension system uses inputs from these to set the ride height correctly. The system has not displayed a fault message, so it seems to think the inputs are OK and the system is working OK.


May I suggest you take it to a suitable shop equipped to calibrate the height settings of the suspension, and inspect the system for damage.

 

I thought about the height sensor being at fault, but that would throw a code or at least at least warning on the dash. Which I have none.

I jacked the car up same height on all 4 ends, I assume that the calibration is fine since all the other ends adjust to full height?? The rear left will adjust to full height but will drop back down about half way.

I don't feel any bumps or anything until normal while driving except the loud whining noise that's quite annoying.

I'm hoping the air bag is OK, because it does not stay slammed to the lowest point but will keep some sort of air in the air shock.

Taking it to the shop will be my last resort as I'm pretty handy at home, just need to know where to start.

 

The whining noise may be air escaping you could try changing the shocks over on the rear to see if it drops on the other side

 

First off, as Fraser says you need to go and drive it for a short distance.

When you jack the car up it the suspension control initially tries to level the car but then 'realises' the car is being jacked up and changes the suspension mode so that it stops trying do any levelling. However, just starting the engine afterwards isn't sufficient to reset the suspension control to its 'operational mode', you actually need to drive the car for a short distance.

If you still have a problem then start looking at height sensors etc.

I had the rear upper wishbones, both sides, changed under Jag Used Car Guarantee when it failed its MOT (the statutory annual inspection in the UK). The rear height sensors are connected to these wishbones. A week or so later when I went out at night I found that the dip beams of the headlights were very high and I had to reset them (quicker than going back and getting them to re-level the car).

 

Partick is right drive the car first after jacking the car up if it drops overnight then you may have a air leak on that shock

 

I am positive it is air escaping. I just can't pin point it!

 

I drive the vehicle everyday for work. It's been 500 miles since it first started.

Wouldn't the height sensor throw a CEL or a warning light from the dash?

I've done the soap & water test on top of the rear shock and air line. Not a peep from them on the top. The whining noise is coming from the wheel well, I do think hear anything from the top of the trunk.

I'm thinking about switching the air shocks to either side and see if the problem persist on the same side or not. I would then know to start looking at the attached suspension on there vehicle rather than the air shock.

If the height sensor can go bad and not show ANY warning light or CEL, then I will try that first.

Any other input from you or anyone else is greatly appreciated & encouraged. Thanks

 

Also, the height sensor will take care of ride height, Not the whining noise that I am hearing, which I'm sure is escaping air. I guess replacing the air shock if bad would take care of both of my problems.

 

So, it sounds rather as if the mechanical side of the left rear sensor isn't working.

From the sensor's reading that the Air Suspension Control (ASC) is getting when you start it judges that that corner is too low and it lets air into the left rear air spring ... and keeps doing so because the sensor output isn't changing. Now I think somewhere I read that after a while the ASC judges that the air spring, just because of the time it's been inflating, must be at maximum inflation and so the ASC locks out and gives up.

My guess is that the sensor arm has become detached from the upper wishbone.

If you have access to a OBD2 fault reader you may find a fault code for it. Not all fault codes give an alarm message, or light the CEL.

If you do find any fault codes there are plenty of people here who can look them up in the workshop manual and tell you what they mean.