Jaguar XJ8 Coil Conversion

Well, about two months and 5,000 miles after our last update, the air suspension in my 2004 XJ8 finally failed. After weighing my options I decided to purchase and install the Strutmasters Air Suspension Conversion Kit.

The conversion kit comes with a pair of front and a pair of rear struts with coil springs, an electronic module to disable the suspension failure warning light on the dash, and printed instructions. I’m not going to post step-by-step installation instructions, because Strutmasters does a pretty good job of it on their site, but I’ll share my experience with the installation and overall impression of the conversion.

 

STRUT CONVERSION INSTALLATION

The rear air springs came out easily and the new struts went in just as smoothly. I noted while everything was apart that the stabilizer links and outer tie rods on the rear track bars were worn, so I replaced them as well.

Unfortunately the front end resisted.

The first issue I encountered was with the upper ball joints, which need to be unbolted to separate the control arm from the spindle in order to drop the lower arm far enough to get the air spring out. On the XJ8 you need to insert a 5mm allen key into the ball joint stud to hold it in place so you can back the 18mm nut off. On one side I rounded the allen key hole and on the other side the allen key twisted up like a decorative wrought iron rail and broke off in the stud. I ended up cutting both ball joint studs off with a cut off wheel.

The front upper ball joints are not serviceable on the XJ8. You need to replace the entire control arm. New control arms come with fresh bushings and ball joints installed. If you search online you’ll find control arms for the Jaguar XJ8 priced between $300 and $600. Ouch. Fortunately, since Ford owned Jaguar during this period certain parts from the Ford Thunderbird and Lincoln LS are compatible with similar vintage Jags. This information does not seem to be available in interchange manuals, but front upper control arms for a 2004 Lincoln LS are identical to those in the 2004 XJ8. I picked up new Lincoln LS control arms at my local chain auto parts store for $72 each.

Moving on from there I had a hard time getting the front lower air spring mount bolts out. There’s one on each side and both were frozen. I was able to break one side free with generous amounts of penetrating oil, heat, time, an impact gun, and a long breaker bar. The other side defeated me, and destroyed two hardened T60 torx drivers in the process. I tried grinding the head off the bolt and driving it through with a punch and 3 lb. hammer. Then I cut the other side off and tried to drive it through. Still frozen. Next, it ate a few high end drill bits. I ultimately had to cut the shock mount off of the shock body, destroy the shock mount bushing in the lower control arm, press the old bushing out, and press a new one in. Then I had to do it all over again because the bolt hole in the sleeve of the URO brand shock bushings was smaller than the bolt. The Beck-Arnley bushings I installed the second time around were a better fit. Did I mention it’s a PITA to press the shock bushings in with the control arm in the car? It can be done with a ball joint press and a short length of notched pipe, but it’s time consuming and tough to do without damaging the rubber on the bushing. And I did end up damaging the rubber seal on the new bushing, so I opted to install a whole new lower control arm with all of the new bushings already installed. Removing the lower control arm is even worse though, as it’s nearly impossible to separate the tapered ball joint stud from the control arm. I wish somebody had told me that before I tried!

 

 

If you’re reading this before taking this job on yourself, had my ball joints and shock mounts come apart easily, this would have been a very straightforward installation. Perhaps a quick corrosion check of your hardware can help you determine if you want to do-it-yourself before your car is up on jacks in the driveway for a few weeks like mine.

Once all of the hard parts are in you may need to install the Strutmasters electronic module to turn off the suspension warning lights on the dash. I was getting three warning lights post installation; CATS System Fault, Air Suspension Fault, and Vehicle Too Low because I damaged the front height sensor mount grinding the shock bolt out. Strutmasters does not provide much information on their site about the module, other than it being included in the kit. I’ll assume that’s because you have to remove the Jaguar’s rear seat to access the suspension control unit, cut the wires to the control unit, and splice the Strutmasters module in with crimp connectors.

The good news is that you may not actually need the Strutmasters module to turn off the dash warnings. I found some forum posts online suggesting merely unplugging the air suspension module behind the back seat and disconnecting the battery overnight to clear the codes would turn off the warnings. I tried, and it did get rid of one warning. On a hunch I then removed the air suspension relay from the main fuse block and that got rid of the remaining lights and warnings. I’ve now been driving the car for a few weeks and there do not appear to be any negative side effects to removing the relay. My car is a 2004. Rumor has it that these hacks may not work in 2006 and later models due to additional electronics that the early cars don’t have. If anybody out there has a later model X350 Jag and has tried, I’d love to hear your feedback.

FINAL IMPRESSIONS

When I was doing pre-purchase research I found several references related to the Strutmasters kit saying that the car sat high after the installation, but settled after a week or two to a normal ride height. That has not been my experience. My car actually sat a little bit lower than stock as soon as I let it down off the jacks. It looks great, but it does appear lowered.

I initially found the ride quality on the Strutmasters kit to be a bit harsh, but after the springs settled for a few days it seems to have smoothed out a bit. I may also just be adjusting to it. I didn’t expect the car to ride as smoothly as it did with the air suspension, but you do feel quite a bit more of the road with the coils. The car handles confidently though. It corners flat and feels much sportier than it did before. In fairness, part of that improvement is surely due to the new control arms, ball joints, tie rods, track bars, and stabilizer links I installed while it was apart.

At the end of the day, the coil conversion eliminates the anxiety of venturing far from home in an aging Jaguar with worn out air suspension components, and that was my primary goal. And though I’m a little bummed that I lost a little bit of the Jaguar’s luxury swagger, I’m curious how the suspension updates will translate on the track. Stay tuned.

By | 2017-09-11T23:29:10+00:00 July 27th, 2017|Auto Projects, Projects and Features|0 Comments

About the Author:

I'm a lifetime car guy with a broad interest in just about any type of self-propelled machinery, and racing. I have a soft spot for under-appreciated marques, which often gets me in trouble with oddball projects.

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