It's hard to tell as I've only ever driven my own XJR, but the suspension feels quite stiff and the car seems to sit high. Sometimes when I switch the car off and get out I can hear it hissing and the car lowers itself to a certain level.

Sometimes if I haven't driven in a few days when I get in it says Car Too Low for a minute or so.

Where should I start fault hunting? Or is this normal behaviour?

 

What codes do you have?

 

 

Hi XJR_hunter,

Diagnosing the air suspension can be daunting. Wingrider's suggestion to have the vehicle scanned for codes is good, but you will need a scan tool capable of reading the Chassis (C-prefix) and possibly the Network (U-prefix) diagnostic trouble codes (DTCs).

I recently diagnosed an X350 that was high at the rear and low in front, and the ride was firm and terribly rough.

The first thing to be aware of is that if the Air Suspension Control Module (ASM or ASU) detects certain faults, it will disable the system so that neither the air suspension nor the ECATS adaptive damping will be operative. The default setting for the shock absorbers is Firm, so that may be part of your problem.

On the vehicle I recently diagnosed, the high rear end was due to failure of the exhaust solenoid valve on the air compressor. The exhaust valve is the only "official" path for air to exit the system when commanded to open by the ASM. If it sticks closed, the system cannot release excess pressure in any part of the system, such as the rear air springs. I happen to have several used air compressors from cars I have converted to coil suspension, so I was able to find a good working exhaust valve to replace the failed one on this car.

When the exhaust valve opens, it is usually for a very brief period, usually only a couple of seconds. If the hiss you are hearing lasts longer than that, it is probably from a leak in the suspension air plumbing, most commonly either at one of the air hose fittings at the top of one or more air springs, from an air spring top seal, or from an air spring bladder.

If you can get the codes scanned, please post them here exactly as they appear (e.g. C2302).

Cheers,

Don

 

This is my problem. I still havent scanned my car however I'm just going to start replacing parts. I have stainless steel sensor brackets that I started putting in with new sensors putting in. Fronts done rears next. I have a feeling its that valve though. Fun times.

 

Throwing parts at your problem can get EXPENSIVE but the LAST part that fixes your fault will be the correct one for the problem.

 

Why not disconnect the exhaust valve solenoid, connect a 9 volt battery and see if it clicks? If not, the solenoid is dead. New compressors are available from relatively low prices and come with new exhaust valves.

If the exhaust valve clicks, carefully remove it and clean all the parts you can. This is easier to do with the compressor on the bench, but it is possible to do with the compressor in the car.

But often, you will save lots of time and money by paying to have the ECUs scanned by a system capable of reading all the codes related to the air suspension.

Cheers,

Don

 

Thanks for this Don. My rear air struts are fully extended and won't come down (2004 x350) for 2 months now. Air suspension fault on the dash. I built my own SDD reader thanks to the kind folks here and a Mongoose cable (not original) and did start the air suspension diagnostics but it would never complete and had an unrecognised electrical fault. I'll have at removing the compressor and check the solenoid - sounds like the culprit as the system has never released air since the fault.

 

Hi jpsmcginn,

Welcome to the Jaguar Forums! It's great to have you with us!

Please visit the New Member Area - Intro a MUST, and post an introduction so we can learn something about you and your Jaguar and give you a proper welcome.

And please let us know what you find when you inspect your exhaust valve. This is how we all learn!

Cheers,

Don