I was starting to familiarize myself with the engine compartment of my new purchase when I came across the item in the attached picture. It is some sort of vacuum valve or switch? I could not find any loose hose that would hook up to it. Previous owner thought it had always been that way. Car runs good. The only numbers I could find on were 12V and TDA 831
Any Ideas.
...Jimmy

 

Looks like the Extra Air Valve that fits into a hole on the back side of the RH air filter housing. It's a friction-fit into a grommet. If/when the grommet rots out, the EAV will simply fall out of the hole.

Cheers
DD

 

Hi Jimmy,

Welcome to forum.
As Doug says I believe this is the extra air valve.
It's purpose is to allow extra air into the engine inlet to raise idle speed when additional load applied to engine by engaging air conditioning compressor.
On the opposite cylinder bank the auxiliary air valve performs a similar function of raising idle speed by allowing additional air bleed into inlet manifold when the engine is cold.

It took me quite some time to stare at my V12 engine and figure out what each part was when I bought my XJS one year ago.

I still haven't identified every part in the engine bay.

 

So...this is suppose to be this way? Nothing hooks up to that open nipple? Sure looks strange.
Thanks for the info...Jimmy

 

Right. Nothing is attached to the nipple. The nipple fits into a hole on the back side of the RH air filter housing. In your case the grommet is probably missing


Cheers
DD

 

Ok...so I probably need a new grommet. I'll go out and open the air cleaner and check it out. Can't stand that thing just hanging there. Need to hook it back up.
Thanks...Jimmy

 

It should be fitted into back of air filter casing

 

I tried to put it in the air cleaner. Soon as I touched it the hose shattered like a light bulb. The rubber is so old it would not even start to bend. So now I will replace the hose. Looks like the air cleaner has to come off in order to have any chance of getting to the connection under the manifold. Oh well...I knew what I was getting into when I bought to old girl. This is part of the fun of owning a classic!
Thanks...Jimmy

 

It is a specially moulded and shaped hose if you get the Jaguar part. Belive it or not, you can get it on and off by putting your hand under the front and along behind the throttle body, without removing anything. As long as you can feel the jubilee clip and the tightening bolt is get-attable, you can get a small socket on it to undo it.


Warning though, if this piece is shot, have you checked all the many other rubber tubes and insulations on the loom??
Greg

 

Thanks Greg...I plan on going through all hoses and lines while fixing this. I see why it is molded to fit, because of the bend under the throttle. Why wouldn't a 90 degree brass nipple and standard heat resistant hose work? Would be a big difference in cost, and maybe last longer than Jag part. I was shocked at how brittle this old one was.
Thanks...Jimmy

 

It would, good point, and maybe the OEM hoes is not available, anyway? On my car you would probably need to buy a hose that had a 90 degree bend at one end to fix it to the spigot, then use a brass bend at the aircleaner end where these is a bit more room. (or even two hoses with built in bends and a straight joiner?). The solenoid would be better poked into the aircleaner I think, that rattling about supported by the hoses only.
greg

 

A lot of dither to provide "clean" air to that valve!!! A low pressure fuel filter would do just fine.


And, it has done well with 'dirty" air. Over engineering???


Carl

 

Just got some hose and an elbow. Used the elbow just under the throttle body, the rest fits fine. Now...where can I get a new grommet for where it plugs into the air cleaner cover?
...Jimmy

 

Jaguar Classic Parts:
Aircleaner-Rh-5.3 Litre - Parts For XJS from (V)139052 to (V)179736 | Jaguar Heritage Parts UK
Part number 12:

Greg

 

If you can't wait for the Jaguar part you can probably find a generic grommet that'll do the job. I did on my V12.

Cheers
DD