Air Suspension Fault

I have a ton of reading to do on this topic, but wanted to post my situation briefly as I dig around and educate myself.

Dreaded air susp fault message appeared on my 140K 2008 XJ8 last night and I tried my AD310 ODB reader with no luck. Read a bit and appears not many OBDs read the Jag prop codes.

The two front air struts were replaced at 100K but two back are original. It appears the driver rear is mostly affected. I took measurements this morning before turning on the car and then fired her up, let run for a bit and then took new measurements.

Measurements are from ground up to wheel arch.

First reading

         Front

27 1/8" 27 5/8"

25 5/8" 27 1/8" // Not a typo… 25!

Second reading after start and idle time

         Front

27 1/8" 27 5/8"

26" 27 5/8"

So, fronts stayed the same and rears went up 3/8" and 1/2". The driver rear is noticeably sagging and almost 1 1/2" lower than rest of car.

So anything to deduce from this? Does this possibly imply leaking rear bag since one of 4 wheels is more affected than others… or could a bad pump (most common issue I believe) end up inflating the bags unevenly.

Also I have a good Jag mechanic, but still expensive. Any idea if pulling true Jag codes will answer any of my possibilities listed above?.. or in other words, are the codes granular enough that it will tell me “bad pump” versus “leaking strut bag”

One last point. When I fired up the car I went to back most sagging wheel and there was a VERY notable hiss of air. Ran around other three and kind of heard air “filling” type sounds, but nothing as loud as driver rear… like a bike tire with a flat losing air. Then the pump stopped pumping as I listened in front and then hiss at back wheel stopped also.

Maybe I can get her up on stands in back, fire her up and see if I can locate the hiss location. Maybe just a hose attached to the strut bag??

OK, thanks for those willing to ponder the evidence… “The game is afoot Watson!”

Randy in Raleigh

Randy,

I’m extremely sure the driver’s rear is leaking because you could hear the air escaping! I had the exact same leakage with the driver’s front. The rear is not nearly as difficult to replace compared to the front. I do not think the pump is bad. If it was, it would not provide the air you hear from the rear shock. I have several used shocks if you are inclined to go that way. I’m in Rocky Mount. A friend of mine who is a tech at Maserati of Raleigh did several coilover conversions to Jags. He sold me the leftover good shocks the customers did not want.

Good luck!

PS I would like to know who your tech is if you would like to share. PM me.

Richard

Stars are aligning! Thanks so much.

I just watched an Arnott video on rear replacement and it looks easy. Also, by chance I go to Rocky mount several times a month since my girlfriend has rental properties there and I get to fix all sorts of house stuff too :slight_smile:

Will PM to continue the discussion.

Randy