Hi,
The front air struts on my 2005 XJ8 don't work.Struts won't raise car.It is not a leaking strut problem,rather that the air inlets are blocked .I removed the air lines and while the compressor is running air with a good pressure comes out of the lines.However I cannot blow air into the struts with an air hose from my garage compressor with the air lines removed and the compressor running.Internal strut problem?
Sounds like I need 2 new front struts.
All advice is appreciated.
Thank you.

 

Air pressure going to any of the struts is controlled by the valve block in the trunk. Compressed air is supplied by the compressor, goes to the air tank for storage and the valve block diverts the compressed air to any of the 4 struts based on the height sensors.

I would start by looking for codes, ensuring power to both your air compressor and air valve block in the trunk.

Additionally, ensure the height sensor in on the front strut is connected. Finally, is the output on your compressor sufficient?

Others will chime in. I doubt both of your struts are bad...

 

I would suspect that yes...you have a problem with the struts...but hard to believe that it would duplicate such a problem on BOTH sides at the same time.

Depending on just what year and month your XJ was built you may have either one or two height sensors on the front. From Dec. of 2003 on they deleted the right from height sensor and the front shocks are controlled by a single sensor on the left that controls BOTH shocks. Given that I'd first look at the left front height sensor and run any pinpoint tests called out in the SVC. manual. To further complicate the situation there were some cars built with 4 sensors but a module that only looked at 3 of them. Jags are so much fun<G>

Since you say you're getting good air pressure through the lines feeding into the shocks (how did you measure that by the way) but you can't get your shop compressor to put air in I have to assume that there's something telling the shocks they don't need any additional air. That points to the height sensor I'd think.

I'm assuming your compressor is capable of at least 100lbs. as most can do 125.

There's an internal pressure retaining valve in each shock but if it works to also keep a shock from being over pressured I don't know but it just might, and if the height sensor is bad or miss-calibrated and telling the shocks their at the right height it's possible that such an over pressure valve would keep the Schrader valve from working.

Could you press the Schrader valve down manually?

 

hI,
Strut inlets don't have a schrader valve.There is just a small,drilled hole above the threaded portion.Nothing to push down.

 

It's not a schrader type, it's lower down inside and it only closes when the pressure inside the unit drops to around 30psi; it's to ensure that the bladder retains sufficient pressure and doesn't go down to 0 psi when the air line is disconnected. It's to ensure the bladder doesn't collapse.

 

My bad as I was thinking of a pressure testing set-up I put together almost 4 years ago when my air shocks started to give me trouble. The rig attached to the air shock at the top so you could pump the shock up to the desired height through a Schrader valve and then leave the rig attached an check the pressure drop over time. Since I replaced a bad air shock with an Arnott unit on the front only to have a rear shock go a few months later I decided to take them all off and replace with a set of Strutmasters coil overs and be done with the fun bags.

As a reminder for those who may have a similar problem here's a link to that long ago post.

https://www.jaguarforums.com/forum/general-tech-help-7/diy-air-suspension-pressure-tester-98790/#post772872
Since that rig was built to test only the front shocks I had to add a couple of more pieces to make it work on the rear shocks as their top fitting is slightly smaller. The additional parts are NAPA #'s although the fitting from the top of a blown rear shock maybe a bit of a problem salvage yards surely would have some or a Jaguar dealer might oblige if you're there personally<G>

 

Good to know. I was wondering how the bladders were protected against full collapse when the top seal was defective. So that means there is still some air volume inside the bladders even when the shocks look completely down?

 

After further testing,I removed the inlet fitting from the top of the strut and with the compressor running air is entering the strut after all.I have 80 lbs of pressure at the strut when the compressor is running and it is a brand new Wabco compressor.
I fitted a schrader valve to the inlet and with shop air pressure applied I am able to lift the corner a max of one inch.Shop pressure is 125 lbs.
Shop doing my repairs has a scanner that can monitor the height sensors and they are operating properly.
Tech informed me that rear struts only lifted the car to it's full height after the vehicle was raised on a 4 post lift.
Hope this new info helps.

 

Tedjan; In your initial post you stated the air-springs were not leaking. How do you know this to be true? With the Schrader valve on the air-spring will it hold pressure overnight? What about when temperature drops? I had an experience where above 68F I was unaware of a problem. Between about 60 and 68F the compressor could keep up with the air-spring leak and after a minute or so the car came up to height. Below mid 50's the leak was so bad I could hear air gushing out the top seal ...ASF.

 

Hi,
What I meant was I am not having a leaking problem because the front struts will not inflate.

 

Replaced front struts with Arnott new units and all is well.