Replaced both front air shocks with OEM Bilstein B4s. Followed the Bilstein procedure exactly. Left the battery connected during the work. The car gives the "suspension low" message but will not turn on the compressor and pump air into the empty front air bags. In the past I have gotten it out of "Jack Mode" buy backing up 10 feet out of the garage and letting it sit 2 minutes and it always comes right up. The problem here is that the Bilstein instructions are adamant that you must never put the weight of the car on the shocks with no air in them. So I can't back it up. I have released the parking brake and shifted into R and D several times. Also stopped and started it numerous times. No love.

My thoughts in order of risk and difficulty:
1. Disconnect the battery and short the leads for a reset
2. Jack up the back of the car and let the wheels spin a little so it thinks it has moved.
3. Drop it on the empty air shocks, back it out and hope for the best.

Any other thoughts on waking up the air system?

Thanks
Jeff

 

Hi Jeff
I thought it would be a good idea to spin the back wheels but I wonder if it would upset the ABS when it sees the rear wheels turning and the front ones stationary. Might still be your best option as the ABS should reset itself.
I had a similar problem with my Wife's Range Rover and I rigged up a connector to gently inflate the bags using a compressor enough to get it on the road, It's a bit of a fiddle but worked ok for me.
I always take the fuse out in the boot when I'm going to jack it up but even that might not have helped you as you would completely deflate the bags.
I think I would go for the wheel spin idea.

Good luck and please let us know how you go...............Hopefully it won't jump off the jacks and demolish something

Pete

 

Pete,
Thanks for your reply. I tried the battery reset AND spinning the rear wheels AND running around like an idiot trying to spin the fronts at the same time all to no avail. Since my initial post I have concluded that new virgin shocks are completely deflated and that is why lowering on them will possibly damage the air bags. BUT, the inlet port at the top of the shock is designed to retain about 45 PSI even if the air fitting is removed. I think (as you say) that if I can get them to take about 45 psi then I can move the car and wake it up! Today I gathered up every pneumatic fitting and tubing size I could find at work (I'm an engineer and we have a good supply of junk around). I also bought some schrader valves so I can attempt to connect the shock air inlet. What I REALLY need is a "Carry Tank Valve ( ) which with enough teflon tape will thread in to the top of the shock and let me easily pump in all the air I want. Unfortunately, one of those is several days away even with fast shipping and I am absolutely done with not having my car for almost 2 months (the whole front suspension rebuild is a long story that I won't bore you with...and I also had carpal tunnel surgery in there so that was 2 weeks of down time ...bla bla bla). So tonight I will attempt to rig something that will let me get some air in there and get on with it.
Regards
Jeff

 

Correct, but Bilstein supply the units with air pressure in them. This is done to ensure no twisting of the air bag diaphragm occurs at any time between manufacture and fitting. When I bought a set of four NOS Comfort units to replace my SPort shocks, there was pressure in them.

 

That makes sense because they are impossible to compress to help put them in. BUT...Then why do the instructions from Bilstein AND Jaguar tell you not to EVER let the car down without full air pressure? Have I been worried about nothing? It seems crazy that they don't have a bump stop somewhere for just these situations. Logically if you had a leak in the air system you would have to replace all 4 shocks because they would have been run without pressure... But nevermind driving, they tell you not to even let it off the jacks until the system raises the car... which it refuses to do. (sheesh)

Jeff

 

Jeff,

The front air fittings are 1/8 npt. So the 1/8 air tank valves will make up fine. Although I can't pull 'em up in house on line, many of the parts houses have them. Or you could use a small ball valve and nipple or add a tee and do both.

My experience has been, that those' check' valves are a horse of a different color. Apparently that little compressor makes head pretty quick.

You may be surprised to see how much pressure those little plastic lines take to lift that thing. (It's suppose to limit at 45, on the way down.)

The goofy part is, that you're getting the 'low vehicle' but the comp isn't coming on at engine on. 'Sure comp power, relays, all that good stuff is in order?

PS: SDD suggests a 3 km/hr roll to assure jack mode is off, FWIW.

 

I rigged up a Schrader valve connected to a 1/8 NPT male thread which fits in the front air fitting really well. Pumped each shock up to 60 psi and then released the supply pressure. You could hear the air come out for a second and then the valve closed and held them (presumably at the spec pressure of 45 PSI) I released the jacks, started it up and backed out of the garage with the "Vehicle Too Low" warning on. Within 10 feet the compressor started and the front came right up. It drives beautifully. Much softer over small bumps, presumably because of the new bushings and fresh rubber in the shocks. VERY happy to have my Jag back up....

Thanks for helping me think it through
Jeff

 

Great to hear that Jeff and some of us (me) have learned from your experience.

The great thing about these cars is that they keep the old grey matter working. There always some problem or niggle that needs thinking about,
I'll be wondering all day why turning the wheels didn't fool it into thinking that it was moving.

 

Pete,

That's exactly it! One has to THINK to solve these puzzles. As amateur mechanics we are mostly doing things for the first time and often with a dearth of information, tools and available parts. To me one of the primary skills of wrenching on old machines is knowing when to stop working and THINK. When the puzzle is finally solved it's enormously satisfying.
I have come to feel that the people who designed my XJ were absolutely devoted to making it fantastic. Often when I'm frustrated by some obscure mis-behavior (mostly Software and Electronics) I later realize that the engineers were doing the best they could with the constraints they had -- OR they were trying to protect me from rare but possibly lethal error conditions that they thought through but I have not. (suddenly popping out of Jack mode while one is working on the car for example)
Also, it is gorgeous.

 

Hi,
if you have an SDD available you'll find a menu for raising or lowering the shocks. SDD is able to trigger the compressor and the valve bloc in order to fill or empty the shocks.

Fritz