I feel that I'm on the cusp of an air suspension issue. Rebuilt the air compressor last winter as I got a "vehicle too low" once or twice after parking on a hill, but never returned after that.

It used to be that when I started off driving the pump would run once (you can hear when it stops, it exhausts for 1 second). Would not run again that trip, and when I parked it would go through its purge cycle and lower the car slightly.

Lately, I can feel the pump running after I've driven a block or two, (vibration in the pedals and steering wheel, and hear it exhaust after 10 seconds). But it will sometimes run 3-4 times, sometimes just once. Don't really notice the vehicle exhausting after I park at home. And I've noticed if I go downtown (bumpy roads, slow speed driving) it will start trying to run again and again.

The car never sags overnight--and it doesn't look any lower than it ever did. I don't understand what it's trying to do (raise the ride height for rough roads?). Seems like it's not able to pressurize something. Never seen any "service suspension" message. Is it time for new front springs?

 

Sounds normal

 

Hi mhamilton,

As Cambo observes, this sounds like normal behavior. While driving, the system relies primarily on pressure from the air reservoir to maintain the ride height, adjust for leveling, etc. The compressor will only run when the reservoir pressure falls below about 145 psi, if I recall correctly, and even then it will only run at road speeds of 25 mph or greater, and it will shut off if the road speed drops below 18 mph. This is part of Jaguar's "noise management" strategy.


That seems strange to me - the air compressor is mounted in the front left bumper and has no mechanical connection to the steering or pedals, so I am surprised that you can feel its vibration. I wonder if the vibration may be originating from some other component?


It doesn't really sound as though you have an air suspension problem. Are you certain it's the air compressor you're hearing & feeling, or could it be something else?

Cheers,

Don

 

When I drive from my house I can just about hear the compressor running for the first

3/400 yards and then I never hear it again so I understand your concern.

Maybe wait for possible plausability code and then persue it?

In the meantime you could change the relay?

 

I know it's the compressor--and yes I noticed that as soon as I drop to 20 mph it cuts out and I hear the exhaust hiss for a second. What I don't understand is why it needs to run so much more lately--I will have parked in a level driveway and go back out 1 hr later, it will run several cycles as I drive out of the neighborhood. But as I mentioned, the ride height never seems to droop when parked overnight or over a long weekend.

You might be right that it has always run this way as part of normal operation, but maybe the "feel" of the compressor is what's new to me. I know the compressor is mounted on springs and rubber bushings, I had it out to replace the seals, but maybe I've got something grounding to the body or something... will check on that.

I guess I will wait for some more definitive fault to occur before I throw money at the issue. I just hate to burn out the pump letting it run excessively if it's trying to compensate for a leak somewhere.

Anyone know if the Jag diagnostic software would show pending faults for the suspension, or indicate excessive run times for the comp? Maybe it sees there's always a loss of pressure somewhere?

Thanks,
-Michael

 

When I put in the new compressor in mine, I had to dodgy up the mounting a little because the bottom mounting bracket had completely rusted away. It's still mounted on springs but it's definitely firmer than it used to be. I can hear it (and feel it a bit) especially when it kicks in/out it gives a little shake.

Hows the weather where you are now? Getting cooler? I find the compressor runs more often in cooler weather than in the heat.

One thing though, you won't burn out the pump, you'll only burn out the piston seal, which is not a big job as you already know...

 

That's good news--I was worried about that more than anything. Yeah, not the end of the world if I have to replace the seal again.

Weather is very hot here, 90-95 F. Will keep an eye on it as it gets cooler. Surprisingly, last winter when we had some days in the teens and 20s F, it didn't really have any issues. As I mentioned, I've never really seen the car droop or sag.

I'll pull the fender well and see if there's any reason for the vibration I feel when the pump runs. Maybe I got one of the rubber bushings in wrong during re-install--I was having a hard time holding the pump, springs, rubber, and getting the bolts started.

Thanks!

 

Been doing some more reading on the suspension system. So the compressor has the exhaust valve internal, and comp. output is direcetly connected to the reservoir. The reservoir is isolated from the air springs by the valve block. The pressure sensor is on the reservoir side of the system. So if I have a leak at the connection between the compressor and the valve block, my reservoir could be leaking down and this might cause the compressor to run excessively just to replenish it. However my air springs do not leak, so any pressure in them stays and the car keeps level while parked.

One thing I did not do was replace this olive at the compressor connection. I also don't remember the olive coming out with the air pipe. Maybe this is the issue and it's a slow leak of my reservoir pressure?