Jaguar Land Rover Classic Parts site indicates that the expansion valve is CAC8169. The Delphi valve on the eBay site is in a Jaguar package. My original valve is made by Delphi. So, there is a possibility that the valve fits. Let us see. As I have reported earlier, the Denso valve did not fit. Luckily, I could return it to the seller.
Otto âŚ
You asked about the blue connector under the MAF. In your picture it looks square ? Anyhow, I donât have a connector in that area âŚ
Dennis,
thank you for checking whether you could find such a blue connector in your carâs engine bay.
Yesterday, I checked the two purge valves of the charcoal canister and the purge valve to manifold with a hand-held vacuum pump and the valves were fine. I did not check the pressure reducing valve since I did not want to open the rusty T-piece and T-piece elbow fittings which are no longer available. I did not notice any smell of gasoline in the area.
I should receive the fuel pressure gauge within two weeks and then I can check fuel pressure and the fuel pressure regulator (FPR). I have sometimes noticed that there is slight smell of gasoline close to the FPR. However, I have disconnected the vacuum hose of the FPR and it did not smell. On Friday, I will go to an emission test in order to check the mixture. As I have said earlier the car runs smoothly and the fuel consumption is proper but the slightly rough idle bothers me still, even if I have checked and renewed lots of typical components and ruled out options. If the cause for the rough idle is not the FPR, then there are not many options left. Of course, there is the ECU. Next, I will clean the earth connections in the engine bay. Luckily, Don has provided nice instructions. https://forums.jag-lovers.com/t/xj40-grounds-earths-locations-identification-service-photos/286238
I sanded and painted the wiper arm and wiper arm nut cover. I used the same graphite grey paint I used for the windscreen cowl. Such small and immediate fixes improve the appearance of the car and make you feel good. I have also recently refurbished the original teardrop wheels using the method by Mercedessource. I have refurbished a set of MB wheels earlier, and this method really works. https://www.youtube.com/watch?v=PMEtayLG8os
After all these years, I have found the vacuum lines get a bit sloppy at the connections and benefit from a 3/4" trim and tighter refit.
YMMV
Larry
Larry,
I believe that is a good procedure.
I have tried to find vacuum leak without success. For example, I have sprayed starter spray around the hoses, intake manifold, and injectors.
I have checked how the idling changes when the spark plug leads are pulled off one at a time. The idling changed drastically as it should, of course, and I did not perceive differences between the cylinders.
By the way, should I remove the bonnet when replacing the condenser? The bonnet is not mentioned in the Haynes manual.
Otto âŚ
I didnât remove the bonnet when I replaced my condenser (or earlier when I replace the radiator) and donât recall there being any clearance issues.
That being said, if you carefully mark the hinge positions with some tape and have a helper holding the other side of it removing the bonnet can easily be done in 5 minutes. And it would make your job much more enjoyable.
Iâll second what Grooveman said. Well worth the time to make a friend 
and remove a few bolts.
Dennis and Mike,
Thank you for your views concerning the condenser replacement. Last summer, I saw a local Jag shop replacing the condenser, and they had removed the bonnet which was resting on a plastic foam on the roof of the car 
. I should receive the condenser this week.
I ordered in a leak-down tester. Even if the cylinder compression test and vacuum gauge diagnostic checks gave great results, I think it is good to perform a leak-down test. If there is a leak, the head gasket replacement and valve job are necessary. Luckily, there is a great case description by Dennis: https://forums.jag-lovers.com/t/water-in-the-oil-1989-xj40-ouch/376624/64
I found a recent video of the valve job: Jaguar XJ40 Valve Job - YouTube
Here are videos of the head and valve job, even if they are for the Series II XK engine: https://www.youtube.com/watch?v=FdSL9fKGSZ4&t=130s
https://www.youtube.com/watch?v=7cFh-u3QXhg
https://www.youtube.com/watch?v=AMgIBVO6OgM
https://www.youtube.com/watch?v=Zs4Tkeel00Y
https://www.youtube.com/watch?v=Rme6I8g6sAo
https://www.youtube.com/watch?v=grxVpJUTsI4
Dennis, did you renew any valves? Steven said here https://forums.jag-lovers.com/t/head-gasket-replacement-cost/387556âI did not cut the valve seats. They looked good with no particular wear or erosion on the seats or the valves and no wear on the stems so I just cleaned up the existing valves and then lapped the valves into the seats, set the valve clearances, and replaced the valve seals when I reassembled the head.â
It is good that I have the head gasket set already, even if I would probably need to buy a new inlet manifold gasket since I have used it already. I have also used the valve cover gasket, but that could be reused, I think. I would need to make a cam alignment tool following Bryanâs measurements, and buy a set of head bolts or maybe use the existing bolts that have not been reused before most likely.
Overall, the head gasket job would be complicated, of course. However, since I have done many repairs around the engine I know how to dismantle many things in order to get to the cylinder head.
All in all, I need to make further investigation before I start to take the head off 
.
Otto âŚ
Again, I am very impressed with your energy and determination in repairing all the problems with your newly acquired XJ40. I love my car and I think all the work on yourâs will be worth it.
Since you did a compression check and the numbers where good I doubt you will be disappointed when you do a leak down test. Itâs easy to get a false âbadâ when youâre doing a compression test due to several factors but normally (almost always) only a good engine will give you a âgoodâ reading. But I always like to do a leak down test because it tells you so much about the engine internals.
Hopefully you wonât have to do a head job but with over a 100k miles and with no real history of how the car was driven and maintained it wouldnât be the worst thing in the world. Trying to diagnose a rough idle is tough but most certainly knowing the head is in good shape is a great place to start. If you do have to go that route we can communicate off line and I can hopefully help you to avoid a lot of pitfalls. Looking back it wasnât that hard.
I didnât have to replace any valves but I did have all the valves faces and seats machined along with new guides and the head decked (all for under $500 
)
My 1990 XJ6 was converted from R12 to R134 by a Jaguar dealer following the factory retrofit booklet which I have and have just reviewed. No mention of changing to an R134 compatible expansion valve. Receiver drier, yes, changing seals in the compressor, yes, some O rings,port adapters, and new type Ester oil.
Dennis,
Thanks for your feedback and encouraging words. It is rewarding to improve the car based on the discussions and valuable insights here. This thread serves also as a restoration diary. Overall, this car is my hobby which means that there should be issues that need fixing. 
Yesterday, I cleaned the earth connections on the left and right inner wings. The right inner wing was greasy, since the SLS reservoir located there until last summer when I did the brake booster conversion. I cleaned the area including the screenwash reservoir filler neck. Once again, the engine bay got cleaner.
Actually, I have quite good service record of the car. The first five years the car was regularly serviced in Illinois. In Finland, the car was maintained by an independent Jaguar service between 1994-2018. The engine oil has been changed regularly. However, as we know the car needed care as I got it, and I felt sorry for the cat. Now I feel I have given the cat a home and attention she deserves. 
It would be great to communicate with you off line if I have to do the head job! Let us see what the fuel pressure and leak-down tests indicate.
I went to an emission test and got the following figures: 700 RPM: CO 0.01 and O2 0.7.
2000 RPM: CO 0.02, HC 17, and lambda 1. Unfortunately, the tester broke towards the end of the test, so I could not get the HC at idle and CO2 figures.
The last official emission test was in July 2019. The figures were: 700 RPM: CO 0.01, CO2 14.5, HC 13, and O2 0.45.
2000 RPM: CO 0.01, CO2 14.8, HC 15, O2 0.5, and lambda 1.015.
John, I have also renewed the receiver/drier, O-rings of the A/C pipes, port adapters, and PAO-68 oil of the compressor, but not compressor seals. That circular base of the original expansion valve has some oil gunge on it. So, it is probably leaking.
I replaced the condenser today. The foam seal of the old condenser was crumbled, of course. I chose not to fit new foam, since the condenser does not seem to move in its cradle, and I do not want to make a trap for moisture between the condenser and the bracket below it.
One thing on my to-do list is the leaking Adwest power steering rack. The rack leaks around the left bellow. I am thinking of acquiring a JLM10838 seal kit for the job.
Otto âŚ
Is your old condenser as clogged up as it looks in the picture ? If so your system was never going to cool very well so itâs lucky that youâre replacing it. Youâll also want to give the vanes on your radiator a good cleaning while you have excellent access.
As far as not replacing the bottom foam seal on the condenser just double (triple) check it doesnât move around and rattle. Once everything is in place and gassed up you certainly donât want to have to remove it. You might consider a thin strip of styrofoam or solid rubber in place of the more porous foam.
I think the power steering racks on these cars are the âBritishâ curse. Iâve replaced mine about 4 or 5 times over the last 30 years but never rebuilt one. Plenty of âhow toâsâ on youtube.
That is one nasty looking condenser 
You can make new condenser and rad lower mounts out of water hose, one inside the other and trimmed to size/shape. Easy and long-lasting.
Man you condenser sure had seen better days! Jeez!
Dennis and Larry,
Thanks for your tips. I added some rubber grommets under the condenser.
So far, the best description of the steering rack rebuild I have found is here: https://www.jaguarforums.com/forum/xj40-xj81-25/xj40-power-steering-rack-rebuild-109815/
Username âxjackâ gives the following advice for the operation:
âI have managed to rebuild my adwest pow-a-rak from early xj40, with help of info given by Glenn Schofield and cause of complete lack of it on the net i decided to share some photos for those who dare to open their one
Here it goes:
In order to take it apart
-remove pinion
-unscrew collar at the passenger end of the rack (did it with clamp locking bolt and hammer)
-remove end
-remove shaft
-push internal tube out with something , no force required (does have one more seal, not on the photo)
Refitting is the reverse of removal and take your time while on pinion it is pain to get rightâ
Otto âŚ
I think thereâs a reason almost everyone rebuilds their power steering pump and no one rebuilds their power steering rack.
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Dennis,
As we know, refurbished power steering racks are readily available for around 300 $ in the United States. However, to import a rack to Europe is very expensive. So, the only realistic option I seem to have is to renew the seals of my rack. To my surprise, my local parts dealer has one JLM10838 seal kit for 43 $.
Of course, it is possible that I fail to make the rack leak-tight. However, I believe it is worth a shot. Here is a detailed video of rack rebuild, even if the rack in the video is not an Adwest rack: https://www.youtube.com/watch?v=NRdLsdymNP0
Otto âŚ
I have no doubt that youâll do a very professional job on the rack rebuilt and YouTube should be able to provide you with any tips and tricks.
http://www.jcsovejag.com/jaguarxj/dossiers_40.php
Hereâs a website Iâve used in the past which has been quite helpful. Although itâs in French you can easily translate the whole thing online. On my Mac using Safari I just go to âhelpâ at the top of the page and type in âtranslateâ.
Dennis,
That French site has some excellent photos. For instance, someone who is about to make the brake booster conversion benefits from best pictures of the operation I have seen.
I got the original JLM10838 power steering rack seal kit yesterday. My parts dealer said that he has rebuilt some Adwest racks and it is not difficult but time-consuming. He also said that the racks he rebuilt did not need any machining. That was encouraging. I have gathered over ten pages of information concerning the XJ40 rack rebuild from different sources. However, one thing that I donât know is that should I use some grease for some parts or should I just use power steering oil for the seals and parts when reassembling them.
I did the fuel pressure check following instructions in the Haynes manual. Most of the measured pressures were correct. One thing that did not work as described in the manual was that when I disconnected the vacuum hose from the fuel pressure regulator the pressure increased from 32 psi (correct) to 40 psi (correct), but when I reconnected the vacuum hose to the regulator the pressure did not decrease (incorrect) but stayed up to 40 psi until I turned off the ignition switch. So, probably the regulator is defective as the system pressure did not decrease. At least, the local independent Jaguar repair shop suggested to renew the regulator when I informed them about this. So, a new regulator has been ordered.
When I turned off the ignition switch and waited five minutes the hold pressure was almost 40 psi. According to Haynes, it should be 21 psi. After two hours the hold pressure was still 30 psi. This is a bit strange. The manual does not say anything about the hold pressure being higher than the specified 21 psi. Well, the positive thing is that the high pressure indicates that there are no leaks in the system. However, after seven hours the pressure was the specified 21 psi.
Here is the T-fitting I used for the pressure test. I believe this picture is useful for others who are thinking how to fit the gauge to the system. You need a M14 female/female T-fitting and a M14 male/male adapter.
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I removed the power steering rack. The removal is quite easy, and the Haynes instructions are good. It is good to have a tie-rod tool for tie-rod outer end removal. I cleaned the outer surface of the rack. Next, I will dismantle the rack. Currently, my confidence level for the rack job is 8/10. Let us see how it turns out.