So here is my problem. However before I start. I haven't heard the compressor come on in a while now. Usually the car will adjust after setting for a while. B4 First starting in the morning as I set in the driver seat it will come on and adjust. So here is my problem the rear seems higher than normal and is stiff as a board. It hits every bump in the road. I tried to bounce the rear and its like the air shocks are full with no travel or give. The front is low. I contribute this to the rear being raised up. I replaced the rear bags (struts) a year ago. I have also noticed a squeaking in the front end like it needs an old fashioned lube job. So is there away to let air out of the rear or do I have serious issues? Can someone lead me in the direction I need to go? Oh BTW no Fault light has come on either.

 

So here is my problem. However before I start. I haven't heard the compressor come on in a while now. Usually the car will adjust after setting for a while. B4 First starting in the morning as I set in the driver seat it will come on and adjust. So here is my problem, the rear seems higher than normal and is stiff as a board. It hits every bump in the road. I tried to bounce the rear and it feels like the air shocks are full with no travel or give. The front is low. I contribute this to the rear being raised up. I replaced the rear bags (struts) a year ago. I have also noticed a squeaking in the front end like it needs an old fashioned lube job. So is there away to let air out of the rear or do I have serious issues? Can someone lead me in the direction I need to go? Oh BTW no Fault light has come on either.

 

Hi westway,

I assume you are not describing a problem with your 1998 XJ8L. If you will let us know the year and model of your X350 I'll start a new thread for your specific issue.

Cheers,

Don

 

I have had a very low ride on my x350, it helped to lift one edge, so it recalibrated itself. You can manually switch on the compressor by bridging the contacts shotly. Than you know at least if the compressor is working or not. Any fault codes present?

 

With no fault message the Air Suspension Module thinks the car is perfectly OK, so it could be your rear height detector(s) that are displaced. Ride height can be calibrated by Jaguar dealers or specialists who have the software to do so. As regarding your "bouncing the car", the CATS system only sets the shocks to 'Soft' when the car moves off, it is always "Hard" if the engine isn't running. There really doesn't seem much wrong with your car that a checkover with the right kit wouldn't correct. A squeaking from the front could be any one of the many joints in the suspension, so again, you need a checkover by an experienced technician. The only really serious squeak to beware of, is from one of the two steel balljoints. If the rubber boots have split and the lube grease has been lost, they can eventually snap and the road wheel go where it likes. Not good !!

 

Possibly a sticking corroded valve in the valve body? but you have the expert on the job with suspension queries with Don B . He knows the system backwards forward and sideways. Dont listen to anyone else .


Lazarus young

 

Thanx Don. I have tried to remove my old car. I guess i dont know how. Currant is 2004 xj8 vanden plas. Thanx 4 the help

 

Thanks for the info. 8 mo ago replace the upper and lower control arms. So I'll look for other wear

 

Hi westway,

I have moved these posts to start a separate thread so we can address your specific issues. A couple of questions come to mind:

1. Have the ambient temperatures in your area been below freezing lately? If so, moisture in the air suspension system may have frozen, causing one or more valves to seize.

2. Have you recently done any work on your car that required jacking up the rear end? If so, the car may be in jacking mode. Usually this will clear once you drive the car a short distance, but if some component is malfunctioning perhaps it is not clearing properly. For example, check that your ride height sensors were not bent or disconnected.

Assuming the answers to the above questions are negative, my first recommendation would be to clean the ground points referenced by the air suspension - the ones behind the right and left headlamps, and the one referenced by the Air Suspension Control Module (ASM) which may be under the rear seat or under the rear right footwell carpet. Proper operation of the system relies on accurate interpretation of the voltages returned from the ride height sensors, and the thin white aluminum oxide corrosion that occurs on the ground points adds resistance to the circuit that can adversely affect the ASM's interpretation of the signals.

If cleaning the grounds doesn't help the car re-level itself, I would highly recommend that you find a local shop with a diagnostic scan tool capable of reading the proprietary Jaguar Diagnostic Trouble Codes that relate to the suspension. These DTCs are Network (U-prefix), Chassis (C-) and Body (B-) codes that cannot be read by most generic OBDII scanners (which can only read the Powertrain (P) DTCs as required by law). See if a local shop has an Autel MaxiSys, Launch X-431, AutoEnginuity with the Jaguar enhancement, or the dealer-level Jaguar IDS or SDD system. Some higher-end Snap On scanners may also be able to scan these codes, though the European coverage of Snap On scan tools is not typically as good as the others previously mentioned.

Capturing the codes may help narrow down the diagnosis. Depending on what the codes indicate, it might be worth another test: Remove the spare wheel/tire in the trunk and remove the foam sound insulation cover to expose the air reservoir and valve block. Disconnect the negative battery cable. On the valve body, identify the smaller hoses that supply pressurized air to the rear air springs, and carefully loosen the brass fittings on those two hoses until air begins to escape. IIRC, these fittings are 10mm, and it's best to use a flare nut wrench if you have one to reduce the chances of damaging the soft brass hex. As you loosen the brass fittings, sense how little torque is required to loosen them - it's not much. Allow both rear air springs to deflate, then gently re-tighten each fitting - do not overtighten!

While you have the battery negative cable disconnected, touch it firmly to the positive cable terminal and hold it there for a couple of minutes to do a hard reset of the computer systems. Reconnect the battery negative cable, start the engine, leave the transmission in Park and allow the compressor to run. Hopefully the rear end should rise to normal height. If it rises but does not achieve normal height, turn off the engine, wait 45 seconds, then restart the engine and allow the compressor to run again as long as it will (up to 2 minutes). The reason I suggest capturing the DTCs before performing this test is that disconnecting the battery and performing the hard reset will clear stored DTCs so you will lose that potentially helpful data.

You may find that the front end just seems low because the rear end is raised to the maximum height. If the rear inflates to the proper level but the front remains low, you may have a leak in one of the front air springs.

If the rear end does not reinflate, you can test the air compressor as Elegancec mentioned in two ways. The easiest is to jump the air suspension relay, which is R1 in the Front Power Distribution Fuse Box. Pull the relay, start the engine, and use a large paperclip bent into a U to briefly jump the terminals in the relay socket that are numbered 3 and 5. If you don't hear the compressor run, you can use alligator-clip leads to supply 12V directly to the electrical connector on the compressor itself (the larger connector is for the motor, the smaller connector is for the exhaust solenoid valve).

P.S. To update the car details in your signature, go to your User Control Panel (User CP button at the left end of the black menu bar above). At your Control Panel, click Edit Signature in the list of options along the left edge. Make your changes in the Edit Signature window, then scroll down until you see the Save Signature button and click on it.

Please keep us informed.

Cheers,

Don

 

Just wondering why you have entered two separate threads on the same subject !

 

Thanks for the heads up, Fraser. I just merged his other thread with this one.

Cheers,

Don

 

Don thanks for all the info. First there are no error codes relevant to this. However I have an engine light on and Im addressing that issue. The mechanic says I have a vacuum leak in the intake manifold. I bought those expensive green seals last week and the long gaskets to fix that problem. Could that have anything to do with this thread or just a coincidence? Yes the rear was jacked up to change a tire last Friday. However I noticed this problem before I had a leaking tire and I have driven around 100 miles after the tire was fixed. Curious, but he asked me if I had a jacking switch. I said no. Do I? No snow here. I Live in Southern California and its been warm up until this week. Cool for us is 75 degrees. Im trying to follow the battery terminal advice. If I disconnect the neg cable and touch it to the positive pole aren't I creating a dead short?

 

Hi westway,

Does your mechanic's scan tool have the capability of reading the Jaguar proprietary C-, B- and U- codes? As far as I can recall, none of the air suspension fault codes can be read by standard OBDII scanners.

I don't think there is any plausible connection between an engine air intake leak and your air suspension issues.

No jacking switch. The ASM does inhibit height changes when it senses that one corner or the entire car is being raised by a jack or lift. This is called Jacking Mode. Typically, the ASM will continue to inhibit changes in ride height until it senses, via the wheel speed sensors, that the vehicle speed has exceeded 2 mph. This raises the question: have you had any issues that could be related to wheel speed sensors, such as ABS or DSC warnings or codes, Cruise Not Available, etc.?

A problem with the rear ride height sensors could be a possibility, but we wouldn't expect both sensors to malfunction simultaneously unless they were hyperextended or otherwise damaged while the rear end was jacked up.

If you think about it, if you disconnect the negative battery cable and touch it to the positive cable, the battery is out of the circuit. The only power sources you will be shorting are the capacitors that power the keep-alive memories in the various electronic control units. Connecting the battery cables drains the capacitors and clears the memories.

I don't know if you downloaded any of the documents I linked to in my post on the air suspension system, but it would be worth downloading and studying the Air Suspension Manual from that post to help you understand how the system operates:

Air Suspension & ECATS System Summary: Components & Operation

Cheers,

Don

 

Forgive my error. I must have missed your instructions on removing both battery cables.

Re-reading it again your instructions say remove only the negative cable. If both are removed then I can see the battery is not a power source. I'll check with him on his scanning device.

Thanks again

Marv

 

Hi Marv,

I did not say that you have to disconnect both battery cables. It's fine to do so, but you don't have to. What I said was, if you think about it, by disconnecting the negative cable and touching it to the positive cable, the battery is out of the circuit (because its negative terminal is out of the circuit, no electrons will flow through the battery). I and many other members have done the hard reset this way countless times with no problem.

Cheers,

Don

 

Today I tried the reset per instructions. Started the car and the compressor didn't come on. shut car off. restarted the car... nothing. My mechanic thinks it is a bent bracket on the left front sensor. My post from Friday isn't there anymore. We are getting readings from all four corners. With the car running he bounced each corner. All but the left front with the bent bracket changed in value. So I'll go back down there next week. What bothers me is the compressor isn't working. But if there are no error codes maybe it thinks everything is OK for some reason

 

The suspension system on these cars are extremely temperamental. Is your suspension light on? These cars will only begin to level once you are above 25mph. Try driving the car around for 1-2 miles at steady speed. These cars misbehave if your compressor takes a long time to pressurize. Cold weather makes it 10x worse.

I just went through an ordeal with a friends 04 VDP. His wouldnt air up, and the susp light was perpetually on. It rode like **** and there was little explanation.
After the rebuilt compressor was removed (and found to be bad) a replacement compressor went on. Once in, the opposite issue occurred - The system aired up fully and wouldn't deflate.

It was determined that the vent solenoid (which is on the compressor assembly) was stuck and not venting correctly. Once the mechanical issues were fixed, the Suspension light was still intermittent. I went into the SDD and reflashed the module and all is well now. We believe a low battery, plus the car sitting for a few weeks aired out some how corrupted the VID block memory for the module.

As long as you have access to SDD you can diagnose and fix this issue; its very tough without unfortunately Be patient and methodical, these cars have hissy fits with low batteries and its easy to throw in the towel.

 

Update: Opened the trunk and let some air out of the rear struts. This did level out the car. But all it did was turn on the vehicle too low error msg. The compressor still not working.

 

Thank you stham. I'll keep all the info in mind. I have to take it in to my mechanic prob Monday. He needs to fix the bent bracket. I guess we'll go from there. I guess getting an error code is progress. Yes it still rides like a truck. But it doesn't look like a Top Fuel Funny car anymore with its rear end up and nose down.

 

OK guys here is one for the history book. My mechanic jacked up the front end and bent the left front sensor bracket back into position.
The instant the jack was lowered the compressor came on. Within seconds the car re positioned its self. Like magic ... Yea
Thanks for everything