My 2004 XJ8's rear suspension is sagging badly on both sides but the front suspension seems fine. The ride is very rough, the bottom of the car is scratching mild speed bumps.
Error codes:
- Vehicle Too Low (red light)
- Air Suspension Fault (orange light) (40-45s after engine start)
- no OBD errors (yet)

Thank you for your help. I appreciate it.

PS: I’ve seen the ASF code before but rarely maybe once every few months.

 

Can you hear your compressor running or not after starting the car?

 

I tried to listen to it yesterday and I can't tell if it's on or off.So far, I started the car 3-4 times for 2min each time and everytime, after 45s, just the ASF warning pops up on top of the VTL warning. The rear suspension's height remains very low, the rear fender covers the top of wheel and the front suspension remains at the same height 1-2 inches above wheel.

 

The compressor doesn't work. The3 fuses related to the air suspension are OK - 1x engine-compartment | 2 x in-the-trunk.
What's next? Please advise.

P.S.: I already have the air compressor rebuild kit.

 

This might be worth trying:

Key off

Break joints to release air pressure until complete system

is depressurised.

Remake joints.

Disconnect both battery leads and touch together

Replace battery leads.

Run engine.

If the suspension partly lifts listen for leaks.

If the suspension does not lift if possible drive vehicle for up to 20 mins.

No guarantees but it has worked in the past.

 

Thanks, for your advice.

I’ve bench-tested the compressor and it’s working. Before I put it back I’ve rebuilt it using the ebay kit.
After I installed it back on the car, it started right away but it stopped after 1-2 min. Waited 1-2 min, restarted the car, the compressor started again.

So I’ve followed your advice:
- released the air pressure from the entire system...by disconnecting the air spring ports from the valve block. The front suspension completely dropped
- Disconnected the battery, touched the leads
- reconnected everything back, double checked the fuses, restarted the car multiple times and nothing happenes
- the compressor doesn’t start, the car looks like a low rider on all corners

I can’t drive over speed bumps so I can’t drive for 20min

Please advise

 

You won't get a true picture of what's going on until you get the faults read with a Jag specific reader (SDD); generic readers aren't too good when Jag specific systems (like Jag air suspension) are involved.

 

icarsoft makes a modest priced Jaguar code reader.
As well as others.
I want to get a dealer level scanner, to program modules.
But that requires a large investment of cash.

 

Have you moved the car at all even a short distance might do it.

 

I couldn’t find a solution to drive my low ride over the speed bumps yet. There are at least 5-6 speeds bumps on the path to the main road. I still don’t understand why the compressor doesn’t start anymore, so today I took it out and I’d like to check its carbon brushes.

do you know what’s the purpose of the compressor’s valve (next to the dehumidifier) and who’s controlling it?

 

Do you know where I can rent one from?
An exact model compatible with 2004 Xj? Most of the cheaper ones are compatible with newer models 2005 and up

 

The icarsoft has issues with reading some engine info on the 04.
That it reads, on the 07, but believe it reads suspension codes on both cars.

 

Hi d0lph1n,

If your car has entered Jacking Mode, you may just need to get it up to 2 mph to reactivate the suspension.

If your compressor ran for 1-2 minutes, don't worry about the brushes. The ASM limits the compressor to 2 minutes of run time to prevent overheating and will impose a cool-down period of at least 45 seconds.

The valve on the compressor is the exhaust valve, which is the only designed route for air to be released from the system. It opens when one or more corners of the car need to be lowered, and it also opens periodically to allow dry system air to backflow through the air drier to partially reactivate the desiccant beads.

This post describes all the system components and operation:

Air Suspension & ECATS System Summary: Components & Operation

If you can find a local shop with a diagnostic scan tool capable of reading the proprietary Jaguar Body (B-prefix), Chassis (C-prefix) and Network (U-prefix) codes, they may help narrow down your diagnosis.

Cheers,

Don

 

Thank you Don for your suggestions. After I rebuilt it, it worked 2-3 times for 1-2 min after I started the car but it doesn’t work at all anymore. Any suggestions?

 

Some of the issues that trigger ASF prevent the compressor from running again until the Diagnostic Trouble Codes (DTCs) are cleared, but these are typically B-, C- and U-prefix codes that require either the dealer-level tools like IDS and SDD, a specialized scan tool like the iCarsoft, or a high-end bi-directional system like Autologic or AutoEnginuity with the Jaguar packages, an Autel MaxiSys, Launch X431, etc. Without knowing the DTCs, it can be very difficult to diagnose and repair these air suspension systems.

Cheers,

Don

 

I had a similar "rear end sag" problem with mine. Turned out to be a bad level sensor and a bad ASM. Repaired fairly cheaply with used parts, never had a problem since. It took a specialist with the proper diagnostic kit to find the problem though.
The exhaust valve on the compressor can get blocked up with gunk sometimes, easy to clean out - just held in place with 2 screws as I remember. This is best done with the compressor on a bench, very hard to get the springs back in place from underneath the car!

 

I had the sagging **** this weekend and couldn't get it to remedy, so I thought I would put the car in reverse and move it 3 feet, then back into drive to go back. Would you believe that it was enough to kick the compressor on and voila back to normal.

Mine looked exactly as you described yours; wheels under the arches by quite a bit.

 

Thank you for all your help. I've decided to sell the car AS IS.

 

Are you sure?
Emotions can cloud judgment.
Right now your pissed,& you just want to be done with it.
Next week you may feel different.
Aren't love & hate, just emotions in overload??????????

 

NO not yet! You're too close.
Check the relay. It's R1 I believe in the engine compartment.
It's the closest one to you on the right of the fuse box when facing the engine.