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V12 Auxiliary Air Valve Rebuild

Paul Hackbart's Guide on How to rebuild your Auxiliary Air Valve (AAV)
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Although this has been discussed several times and the archives retrieve several documents regarding it, as well as the XJ-S book, the descriptions were very difficult to visualize and made little sense to me. This is my second XJ-S and tinkering on Jaguars for several years now, I couldn't really upon removal and inspection seem to figure out how this thing could possibly be rebuilt/taken apart. People talk about grinding areas off, making a tool to push piston out through the holes, and I don't know what a "spigot" is. I even read a description of a "vagina looking slot" enticing but difficult to visualize. So here you are:

BRIEF DESCRIPTION: Goto the Home Page and read the XJ-S book, a description is listed there. If you haven't and know about this site, read it all NOW(or ASAP) thoroughly it is indispensable as everyone knows. Since your here though here is a brief description to help my further instructions later on. AAV located on left (driver's side -USA) bank behind induction manifold. Upper hose connects to overrun valve on manifold, horizontal hose connects to air cleaner assy. From this horizontal neck which attaches to air cleaner is where air flow is regulated via a 13mm nut. Remove/disconnect both hoses and loosen both torx screws. If you haven't a torx set, a #4 allen wrench works just as well. Upon removal, look down through the body of it from the top. You will first see a spring and further down a disk like piece with six holes in it. This is no disk and is not a separate piece, it is act ually the piston and is about 1 1/4" long. This closes the air passage way which you adjust w/your 13mm nut. As you look down in from the top, in the center of the piston you will see the top of the thin rod that comes from the thermostatic bulb and raises with increase in coolant temp. So, as the coolant warms the little rod from the bulb at the bottom pushes upwards, pushing the piston upwards closing the horizontal passageway. As it cools, and rod is relaxed from the thermo.bulb the spring pushes the piston back down to fully open again. Turn valve upside down this is the thermostatic bulb which fits in the coolant rail. There is a degree C rating (apparently they vary w/model year. Mine is 30C) at the end. See the circumference around the bulb (about 1/4" thick)? This is not part of the valve body casting, it is part of the bulb, they are one piece. It looks like there is no way to take this apart but you can. A piece of grit can seize this "slide valve", you may find a lot of crap in there too as it is on the same side as the PCV valve so oil residue may get sucked in it which is usually what seizes it. You RARELY EVER have to dish out the $189 to get a new one(that's the cheapest I've found for one).

STRIKE ONE: Firstly, if you have high idle, double check throttle/butterfly adjustments and that throttle micro switches are working and coming into effect when they should (I have a 1990, there is a throttle micro switch directly above AAV that was NOT adjusted properly and that alone dropped it down 3k). To diagnose AAV, when engine warm remove air cleaner, no/very little air sucked through the hole the horizontal hose connects to, if there is, AAV seized/stuck. Do not make a little tool or use little rods to insert into holes to push the thermo. bulb assy. out, don't waste your time. (#1 if you can find something strong enough that won't bend and will fit in those tiny holes w/out bending to push bulb out my hat is off to you, #2 I tried this reading The XJ-S book and damaged the entire area surrounding the rod and screwed up free movement) Use a long socket and punch, or socket extension to use piston to push thermo. bulb assy. out. Once that is pushed out, everything else comes out with it. Do not use just a cylindrical punch as if you punch down on the center rod in the center of the piston you will damage the thermo. bulb. Just clean everything out, use super fine sandpaper to polish everything up and I used Marvel Mystery oil on reassembly as I had that around for some reason, but a thin oil is fine if you want to use it. Get a small pot of water over your stove and hold bulb end in water and hopefully watch piston push all the way up. Then put end under cold running water.It cannot go down by itself (that is why you have the spring remember) so gently push it back down. Mine did not raise up all the way and no you cannot get replacements for the thermo. bulb only. As mentioned earlier, mine got buggered up by using a punch (I had to grind it down to small dia.) to push bulb out. It moved about 1/4" , hell I'm out of luck. Well.............if you have NO movement you are. Sorry.

STRIKE TWO: As the manuals say, reassembly is opposite of disassembly. Just close your vise enough to give some space around the bulb at bottom and hit valve assy. from the top thereby pushing bulb back into place. Hold again in hot water and see how far your movement is by viewing through side opening. Now, compensate for the area that doesn't close by going back to your vise and turn AAV upside down with bulb up. Get a long socket that fits around bulb and using your big hammer drive the entire bulb assy. in to compensate for the area that did not close. Now go back to your hot water and check it out. Good deal. Also, I might add how some areas like this that you don't disassemble often and don't want to waste time in making gaskets, I used an "instant gasket" compound that shoots out like whipped cream and dries in 5 min. I was skeptical using it at first, but it works very well. Reading the bottle they guarantee that it will last longer than a standard paper type gasket, etc. Last time squirted a bit on paper to gauge how long it took to actually cure. I torqued down screws just slightly to allow to dry and left an hour (I say I was skeptical) and came back and retightened fully. This time I torqued it down completely (as per instructions) gave it 5min. and worked great. You can get it at any parts store. You also really don't have to worry about the empty area you now have as you pushed valve assy up . I filled with this with gasket stuff just for whatever. I would would have preferred to use washers to fit around bulb, but couldn't find any at the time.

 

 

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