This thing, right?

I was confused about it as well. Except in my case, the unfiltered side is open, the filtered side is connected to the air pump, so perhaps your connection has been put in the wrong one.
Or mine has....
Actually, no. Jaguar Classic Parts shows the inner side one as the being the Supplementary Air Valve. It doesn't show the rubber elbow grommet leading nowhere, however. It is shown, but not labelled, on the JaguarSport aircleaner, however. So I'm curious to know what it is myself....

 

Konichi Wa! And thank you for your reply. Domo arigato!

I reviewed your question and I may have an answer that I found in the Jaguar XJ-S Repair Operation Manual, in the Supplement C,

According to what I infer from the Supplement C, the Jag XJS v12 was upgraded in 1993.25 to a 6.0 litre engine. The items in the supplement C are specifically listed in regard to the 6.0 litre engine . I don't know your engine type, nor the model year, but mine must be the 6.0. According to the supplement, the "Cold Air Intake" was altered beginning 1993.25. The alteration was intended to bring more outside cold air into the engine for combustion because the outside cold air had a higher oxygen content. Did they alter the air filter system? Apparently yes. Figure 1 in the Supplement C for the 1993.25 changes include the diagram below. The driver bit is pointing at the right side(passenger side) air filter housing, specifically the side of the filter housing adjacent to the engine, where the mysterious rubber elbow grommet is attached (on our vehicles). But notice in the diagram that the rubber elbow grommet does NOT exist?

Look at the diagram, please. Does it appear that there is a hole in the housing - or is it a plug? I say it's a plug, because there's nothing attached to it. Do you concur? If so, then why would our vehicles have a rubber elbow grommet attached to the inner housing? I can only speculate. But I think it's reasonable to think that the Jaguar assembly factory had many numerous air filter housings and it's possible that many of the housings already had the rubber grommets attached because prior to 1993.25 - that's what was being assembled. I figure that in 1993.25 the assembly line person or people who were assembling the 6.0 engines just continued using the housings with the rubber elbow grommets because that's what they had been doing for many years. But instead of removing the grommet and installing a plug, or a seal, they just ignored the elbow grommet - until a quality control technician came to inform them they were doing it wrong. But by that point many 6.0 liter engines had already been assembled and shipped off to where ever they were going for further assembly.

Here we are - 25 years later - trying to figure out the problem.




Photo below is in chapter 3 of the Supplement C and appears to me to be specific to the 6.0 liter engine. Notice that on the passenger side there is only 1 Crankcase Ventilation hose attachment? That would confirm that the passenger side of the air filter system was NOT intended to have a rubber elbow grommet. Right? Because if there was supposed to be a tube connecting the rubber elbow grommet - then it would have been drawn in the Figure 2 crankcase ventilation diagram.



So, unless you - or any body who has more experience than I, has any objections - I intend to remove the rubber elbow grommet and seal the hole with plug.

So what is the rubber elbow grommet in YOUR photo? I believe that is the grommet for connection to the air pump, and that grommet is attached to the NON-filtered side. But I have not confirmed that yet. Nor will I confirm anything on your vehicle until you confirm the model year and engine type. If so, I might be able to find the correct diagram in my operation manual.

 

My engine is the 5.3 litre, as you can tell from my signature (you should also create a signature with your car's model year and engine type (V12, I6)). It definitely doesn't have any extra hole on the inner surface, although that diagram on p.436 of the ROM does show a circle roughly where my car's air temperature sensor is. Actually, looking at diagram on p. 445, there does appear to be an elbow hose on the inner surface just past the supplementary air valve. It's hard to tell as the diagram isn't that clear, and I'm fairly sure mine doesn't have it. It's not shown on the 6.0 litre diagram on p. 455.
There's also what looks like it might be a bung in Fig. 14, p. 450.
It may be that Jaguar simply had extra stock left over with the extra hole, and for some reason instead of simply plugging it, they added this rubber elbow.

Also note that in my case, the elbow is on the OUTSIDE casing, like in the JaguarSport diagram I linked, but I have not found any mention of it in the ROM. It's not the air pump connection (supplementary air valve), as that's on the inner side and is connected up. Though logically, it should be on the outer side so that air from the air pump can be filtered as well. But nope, that's where it goes....

 

Ok that's right Someday, I can see your signature and I infer you have a 92 xjs v12 5.3 l. My repair and operation manual does cover that engine. And chapter 2 of supplement C covers "Emission Control System 5.3 litre 1992 model year on".

Here's the diagram in my book for the CV crankshaft ventilation system. ooops, I got them uploaded in bass ackwards order. Well, cheerio! I am not competent to opine, but I infer based on my review of the diagrams below, that your engine has 1 air filter housing? The outer 1/2 of the housing (ie the part that you can remove for air filter replacenment) is NOT supposed to have a rubber grommet. But the inner housing - which I believe should be bolted to the throttle valve - should have 2 holes, (possibly 3), possibly each hole with a rubber grommet. And those grommet should connect to tubes leading to 1. right manifold 2. left manifold 3. engine breather filter.





If you desire a better photo of the diagrams please message me. Otherwise, I'm signing off for the evening.

 

I don't follow what you mean by "one air filter housing". It's got two, one for each bank.
As I understand Fig. 4 on p.438, which is helpfully not referred to at all in the text, it's the left-hand (port) air cleaner, so the number of grommets doesn't have to be the same as the starboard one.
My car's currently in the shop, but once she's out, I'll take an even closer look at the starboard A-bank air box.

 

 

I have some early 6lt air cleaner covers on my 84 5.3 they have no extra holes in them or in the back plates which I havnt used as I have no abs. I was told they were from a 92 uk my, if this helps. they both had a SPE label on them which means they are sports 6lt. also both have the threaded holes for air temp senders, but were the R.H. one goes is anyone's guess.

 

All the diagrams I've seen, both in the ROM and at Jaguar Classic Parts, say that the supplementary air valve from the air pump is definitely on the inner side, so I wouldn't worry about that. My strong suspicion in your case is that at some stage there was another hose that connected to the inner side, and Jaguar simply had lots of left-over casings. Or it is used for something on the V12 saloons. In my case, with the external rubber elbow leading to nothing, the JaguarSport diagram at Jaguar Classic Parts shows the exact same thing, so I might assume when making mine they grabbed a JaguarSport one by mistake, only the trumpets are standard, not Sports.
I suspect we'll have to wait for one of the veteran experts on the forum to chime in....

 

Hi Someday,

I'm still trying to review the manual. Both the 5.3 for you and the 6.0 for me. But I need more time to review it. I don't want to make mistakes. However, I'm rather certain that the inner side - the "back plate" of the air filter housing has a grommet to connect to the air pump. The air pump sends air to the "air rails" which is for combustion, so it must be filtered and clean. The rubber grommet on the outer housing the "cover" can be open and it may not seem to matter because that's the unfiltered air side. Plus, I think I ran across a comment that the rubber grommet on the cover (out side) is an "overflow" tube. That could be important if you are driving in the rain and a lot of water got into the air intake pipes. Where would the water go? If your over flow tubes are open, then water would drain away.
I'm switching my air pump to the INSIDE grommet. Previously, my air pump was connected to the outside. But I want to pump clean filtered air into the engine.

 

Oddly, the message my email said you wrote isn't the message you posted here. I guess you completely rewrote it. Weird how it showed like that, though. Anyway, I'll respond to this one showing here.
I agree that the air pump should have its own filter if it feeds to the air rails--though I wonder why it's never mentioned that I'd come across. So that means, theoretically, clean air coming into the filter. Though in my case, it's not entirely clean--see the photo:




That sooty patch is where the air pump connects. I don't really know why it should be black like that.

I don't think that outside elbow pipe can be a water drain, however--it's too high up, and only on the A bank cleaner box as far as I can remember/tell. It's likely such a thing could be useful, but I wonder how much water would be sucked up based on where the inlets are. If you could find that comment again, it could be useful.

However, based on everything I've found, both in the ROM and the online diagrams, you're right to switch to the inside grommet. Although since the outside grommet air goes through the filter anyway, it might not make much difference....

 

pic of my early 6lt cover

 

 

 

hope these pics can help, the backs came with them but aren't being used, there is a grommet in the back of the right hand back plate which can be seen in pic that ime pretty sure my original 5.3 U.K doesn't have,

 

 

I got my engine lines re-assembled today and started her up. Yeah! I had a tough time getting the auxilliary air pump connected to the tube, and then up to the air filter housing back plate. But eventually I got it in there and it is a good fit.

As to the stain on your filter. Can you try to determine whether it's oil or carbon? Is it dry and powdery? Or is it greasy?

 

Probably carbon. Definitely sooty. Rubs off on my finger.

 

Hey Someday,

I was contemplating your carbon build up on the air filter. It occurs to me that you may want to consider whether the hoses are installed correctly on your air pump. Why? The suction created by the engine combustion should be pulling every speck of filtered air out of the filtered air reservoir, and into the combustion area. But somehow, (based on the description you gave) carbon-loaded air got through the grommet in the reverse direction and across the filter-air reservoir and onto the filter. Right? In order for that to happen there would - in theory - have to be more pressure in the air pump hose than there is inside the filtered-air reservoir. I can only imagine 2 scenarios that might cause that. 1. The air pump hoses are reversed. Instead of pumping air from the filtered-air reservoir into the air injection system - your pump or the hoses are reversed so you would be pumping from the air-injection system and into the air-filter system. 2. The other scenario might be that the air rail check valve is stuck closed. That would prevent the pump from pumping air into the air-injection system and might create a backflow into the air filter.

 

Thanks for your speculations. I don't quite follow you, however. As far as I can tell, the obvious way for the soot/carbon buildup is for it to be blown there from the air pump when it's turned on. It's right where the air pump pumps extra air into the air cleaner box. Uh... the air pump does pump air into the air cleaner box, right? I'm starting to get confused....
Okay, checking and researching, and watching , (why does YT video post as an inline image??) the secondary air pump takes air OUT of the air cleaner (hence being on the filtered side, I guess) and passes it through the air pump to the exhaust to control start-up emissions. Hmmm. I was completely backwards. So why is it sooty? It's like exhaust soot is being blown into the filter, indeed, as you suggest.
I don't think the hoses are likely to be reversed, but it wouldn't hurt to check where they actually attach to the pump. Could someone have connected them up backwards and put the thing on sucking air from the exhaust to the filter?? Sounds like it would ｆｕｃｋ up a lot more things if that were the case. The air rail check valve being stuck shut is a possibility, indeed. Hmm. This mystery might actually warrant its own thread. Once I get the car back--god knows what's taking so long.