'89 XJ40 Power steering rack high pressure o rings

OK … I am officially frustrated !

I recently replaced my adwest power steering rack (leaking into the boots) with a rebuilt ZF unit.

Everything went smoothly and I drove around for about 30 miles making sure I did plenty of lock to lock turns with zero leaks … Next morning looked under the car and still no leaks but after driving for about 10 miles BOTH fittings leaked severely when steering wheel placed at the lock.

Pulled off the two pipes and closely examined both the O rings (that came with the replacement ZF rack) and the fittings. Everything looked normal. So I went to my metric O ring collection and found two that looked like a good fit. Installed them and again everything worked perfectly with zero leaks after I put it through a long thorough test drive. Next morning still no leaks until the afternoon when both fittings started leaking significantly. Horrible Deja Vu !!!

I talked to the company that I purchased my rack from, Advantage Steering in California, and they couldn’t give me any explanation why this would happen. They did however say they would send me two new “fatter” O rings.

Does anyone know the size or part number for these two different sized O rings ?

Does this make the least bit of sense to anyone ? Remember there was never a leak at this location on my old rack, so I don’t believe the two high pressure pipe ends where the o rings go are the problem.

Any insight much appreciated (all my wife could do is hug me and tell me to hang in there :smiley:)

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I know the O-rings in the 94 R134A A/C lines are peculiar - the large assortment in my shop plus a visit to NAPA couldn’t match them up. They’re metric but not sized like any spares I ran across. Ended up using old ones. Not that helps any, but now you know you are not the first lol

What’s so bizarre about this is the fact that there was absolutely no leak at first after driving about 30 miles and purposely steering the car hard lock to lock many times. And then the next afternoon both fittings started severely leaking when turned to full lock. Not just a slight weep, but a real dripping leak both around the threaded portion and the area where the metal tube goes in. And the same exact thing happened TWICE with two different sets of O rings.

Screen Shot 2022-04-23 at 6.35.38 PM

Is it somehow possibly that the rack is being over pressurized ? Again I didn’t have this problem with the rack I just removed so I believe I can eliminate the power steering pump as the culprit.

Groove, let me first say I have no, zero, nada, zip experience with PS racks. I imagine there are plenty of folks that have replaced an Adwest rack with a ZF without complications. However, after doing a little online research into hydraulic fitting types and the different methods of sealing I wonder if the ports on the ZF rack are the same as the Adwest rack. If so (and I would expect they are) is it possible the seats (sealing surfaces) in the ports are damaged? Just spitballing here…

Hi Groove, did you use O rings from the same supply both times ? I’m thinking maybe the O rings are reacting to the PS fluid and softening up after a while in contact with it. Did they look swollen or affected in any way ?

Gents thanks for the replies …

Well I decided to give it one more try before I really go crazy. So I again disconnected the two offending high pressure fittings and very carefully checked for any visible damage. Everything on all the mating surfaces looked fine (I’m discounting any problems with the two metal lines since there was no leak there with the old rack).

I very carefully matched up two new O rings and put everything back together. Just got back from a 30 minute test ride … no leak. While the car was in park I went from lock to lock about 10 times and held it there for a few seconds to apply maximum pressure to the seals … no leak.

I should be happy, but I’ve done this twice before and the same thing happened, everything leak free and then the next day the dam breaks. Fingers crossed this time but I’m not holding onto much hope.

The 2 O rings that came with the rack I tossed after they leaked (whish I had kept them now for size comparison). I did call the company that I purchased the rack from and they’re sending me some replacement O rings.

Good Ole Classic Jaguar diagram for my year shows the same O ring for both pipes (red arrows 15) so that isn’t correct.

Screen Shot 2022-04-24 at 5.52.52 PM

The only different O ring in the diagram is #14 (black arrow) but that appears to go to the pump.

Casso … The O rings looked fine and I can’t believe they would deteriorate overnight. Not sure what material they are other than automotive O ring stuff :grinning:

Screen Shot 2022-04-24 at 6.52.31 PM


So day two and after driving the car several times … absolutely no leak. I am now cautiously optimistic.

I do not understand this at all and it makes no sense !!

Groove, do NOT try to understand the great and wonderful Jaguar god, do NOT question why, merely turn and face Coventry, bow from the waist, and say slowly and reverently “O great and powerful one, I am not worthy, thank you for hearing and answering my humble plea…[repeat twice].” Follow this with an ample donation to Jag-lovers and who knows, the next time you’re faced with one of those indecipherable problems the great and powerful one may again smile upon you. Can’t hurt, anyway!


Mike …

Funny you should suggest that because lately I have been doing quite a bit of bowing to the Coventry Gods … but it wasn’t my face that was pointed toward them.

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Ahhh grasshopper - you were doing the great circumnavigating bow. Namaste!

So to get it straight in my head there is a direct replacement ZF rack for the Adwest one the car came with? Hose fittings are compatible assuming the correct O rings? I ask, as my car 1990 car (74K miles) is still running its Adwest and, touch wood, no issues but I like to plan ahead. I am quite pleased with the ZF one I fitted to my 1965 3.8S a number of years ago when I went to a rack system.

John …

Yes you are correct Sir, there is a genuine (because the letters “ZF” are casted into the tower) power steering rack available for my year model '89 car.

I just installed it (fits like a glove), and finally got the proper O rings, so no leaks. Classic Jaguar website list the same rack(s) used for '87 to to '94 XJ40 models so I assume mine would fit your '90 with no problems. I had to pay a $150 upgrade over the Adwest unit to get the ZF rack. We’ll see if it’s worth the money in the long run.

Question … I couldn’t find it anywhere so how did you determine that these cars originally came with Adwest units ?

Good news is that the power steering rack is still not leaking, so I’m going to put this in the “DONE” list.

The only thing I did differently on the 3rd try was to move the 2 pipes back and forth to make sure they were properly seated just prior to tightening the fittings.

I don’t understand it but I can live with that.

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I have the same problem. Finally got that o ring to seal but now both ends of rack leaks. Was thinking to much pressure also.
Going to rebuild the rack my self. I read some place that there is a pressure valve on the output of the pump.