XJ XJ6 / XJ8 / XJR ( X350 & X358 ) 2003 - 2009

05 VDP air loss

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  #1  
Old 08-20-2020 | 01:05 PM
Estam's Avatar
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From: Port Huron, Michigan.
Default 05 VDP air loss

Experiencing air loss from front suspension system. Starts up, pumps up and drives fine. Overnight front lowered, same both sides and rear is fine. Our Jag dealer is over 2 hour round trip and two local garages have some experience with these vehicles and neither could find a leak in the front system. Any suggestions on what could cause this? I'm suggesting that the obvious has been checked so maybe someone could shine a light on something less obvious. Many thanks...
 
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Old 08-21-2020 | 10:44 AM
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I'll bump you up, 'till a more experienced helper comes along.

Your system's the same as one I'm correcting.

If they/you have not been under the truck cover, the easiest hope is a leak in the line to the front right air spring.

Conventional wisdom is that both sides lift / fall as one... but there are two valve ports, one for each side. The fronts are the larger lines with 12mm fittings.

The right side valve port is to the left center. It will be tagged in yellow.

A bad o-ring/leak at that joint, or from there to the air spring, fits your symptoms.

(Yes, the reservoir tank and solenoid actuated valve block are under the center of the spare tire.)
 
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Old 08-21-2020 | 06:14 PM
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Sounds like you will be replacing those front shocks.
Not what you want to hear, but they do wear out.
Arnotts are what i replaced mine with, & they work well
 
  #4  
Old 09-03-2020 | 03:50 PM
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The easiest hope is a leak in the line to the front right air spring.

Conventional wisdom is that both sides lift / fall as one... but there are two valve ports, one for each side. The fronts are the larger lines with 12mm fittings.

The right side valve port is to the left center. It will be tagged in yellow.
A bad o-ring/leak at that joint, or from there to the air spring, fits your symptoms.

************************************************

Thanks, both front shocks have been replaced that's what makes this so frustrating.

Have a quick question to Revovator, <post above> was a good post and passed it on to the tech. The question I have is you explained two lines from each front shock goes to there own position on the valve block, my question why do both go down if there is a leak in the right front line?
Many thanks....
 
  #5  
Old 09-03-2020 | 05:22 PM
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Estam;

If you really want to understand this system better study the "Air Suspension and ECATS....." thread found in the "Stickies" section at the top of this forum.
It's a long read but Don provides a really good summary and links to other resources.

Air Suspension is a common issue and many forum members have dealt with it. In my particular case a leaking airspring followed a year later by a worn air compressor ( 85 kmi and 14 yrs on the car).
When you park your car it attempts to level, and then 'wakes' at intervals and re-levels. A leak in the system quickly depletes the reserve air in the reservoir and I seem to recall at some point, the ASM failing to level by increasing air in low corners, will result to bleeding air from high corners. I believe your '05 will be a 3 sensor (as opposed to 4 sensor) system so air pressure is adjusted to both front corners at the same time.

If you have a code reader with live data capture you should be able to detect which corner is leaking after the car sits for a few hours but then you still need to identify where.

You don't say how many miles on you car but airsprings are known to wearout from use and the rubber seal cracks over time.
As Wingrider suggests, lacking any additional data or clues it is likely a leaking airspring.

Best Regards, William

 
The following 2 users liked this post by wwr:
AD2014 (09-13-2020), Don B (09-13-2020)
  #6  
Old 09-12-2020 | 12:09 PM
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For your sake i hope it is a simple air leak someplace. If not, take a look at the Arnott coil over conversions. They sell replacement air springs as well but the entire conversion kit is about the price of one air spring. I have an '08 VDP - at about 150K miles the front started dropping overnight. Finally would not pump up enough to avoid the low warning light. My independent mechanic recommended replacing both front air springs - then i started thinking about the remaining two original air springs in back....then started to think about the original air pump in the trunk with 150k on it. The $ estimate kept getting larger and larger. My mechanic recommended the Arnott Coilovers and I have been pleased. I don't have any hard data but I sometimes think the ride is not quite as smooth and/or controlled as the air springs but it may just be in my head. All in all I have been pleased having put another 20k+ on them.
 
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Old 09-12-2020 | 09:13 PM
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From: League City
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Estam,

My apologies. I had not seen your question. (It's fine to tickle me, with a PM if I go dark.)

Realize I don't know in the traditional sense. The lit is scarce as are line drawings.

It acts like and logic confirms that both yellow and brown ports open together when flow is toward the springs. That allows for the deletion of the fourth sensor.

So, a leak anywhere along that trace, will drop both sides when it's set to fill.

Mine specifically drained both sides faster from the yellow port. We now know that my sit was hampered by the played up air valves. One did not exhaust fully. Until years later, when it did.

(These are only two years old with low miles.)

Honestly, I've messed with fluid systems for a long while, and these fittings confound me. They seal with an o-ring at the threads. I 'guess' they seal at the tube by internal pressure helping to swell the tubing... 'cause what I assume functions as a compression piece, is slotted. It' s not continuous.

I would think after a few on and offs they'll leak. (I may be dealing with something like that now.)
​​​
Yeah I can loosen any fitting on the yellow or brown lines and the front will eventually drop.

The rear will stay where it is.

So yours could be a chafed plastic line... anything.

With some 1/8 ips fittings you can test your springs. A tee, a gauge, and a valve.
 

Last edited by Renovator; 09-13-2020 at 12:00 AM.
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