I got some MANN air filters for Lady Mary, making sure the part number (EBC1084) matched. Today I finally got around to trying to replace them. To my surprise, the air filters were in opposite directions. The RH filter (looking towards the front) was with the metal plate at the back, over the butterfly valve area, while the LH filter was with the metal plate at the front.

There is an arrow and a label saying "FRONT" on that metal plate, so I assume the arrow points to the front, so it's probably pretty clear that the metal plate goes at the back on both sides. No idea how long the LH one was in backwards, however. Hopefully it wouldn't have harmed the engine too much.... Is there anything I need to watch for or need to get checked by someone who knows what he's doing, or is putting it in the wrong way just restricting flow or something?
(I'm probably stupidly paranoid and overthinking things, of course.)

And the black soot on the RH one makes me wonder if there's anything amiss there as well. I'm not sure if it aligns with the loose plug (a secondary air sensor, not the AAV) that was fixed soon after I got the car.

 

no harm done but the risk however remote is that the paper get sucked into and jam the throttle plate hence the requirement for metal section be opposite throttle.

 

Ah, that's good to know. I wasn't sure exactly why the throttle area needed to be metal, but your explanation makes perfect sense.

The other reason I was concerned was that the Jaguar XJ-S V12 Service Guide PDF that's available for download elsewhere on this forum says that Marelli injection filters have a blanking plate about a third of the way down, as seen here (http://www.jagshop.co.uk/images/dyn/EAC1828.JPG), but the part number from Jaguar Classic Parts is clear: this filter has no part-way blanking plate. Is Marelli injection then not the same as as a Marelli distributor? Or is the PDF wrong?

The soot on the RH filter appears to correspond to the hose/pipe in this photo, with the smaller dirty area being the small plug with the wires.

 

The metal portion of the air filter goes against the throttle plate. That way if there is a ever a backfire the flames are spit out against metal, not paper.

I think that hose is from the air injection. It runs for 45 sec or so on startup to light off the catalysts and then dumps in to the air filter housing. Your car may be different, as it differs with the different emissions schedules. Nothing to worry about anyway, perfectly normal.

Usually pictures have [img] in square brackets and then a URL followed by img again. If you delete that line containing the img's and everything in between you should be able to delete your photo, then paste with the correct address to edit.

 

Thanks very much. That makes sense as well. The thing I like about learning these facts is how they work to make the engine seem more logical and understandable. There's reasons why it is the way it is, but the reasons aren't always immediately obvious to novices....

I definitely have the air pump, and the cats. Not sure where that hose goes, or why it should blacken the filter, but so long as it's all normal, I'm not worried.

When I clicked on "edit" before, I could select and delete the photo, but for some reason it wasn't working. Nor can I delete actual posts, despite the "edit/delete message" popup message. But I've managed to delete the photos now, after restarting Firefox.....

 

The other thing you'll notice is the left air filter gets dirtier faster than the right. That's because all the air that goes through the axillary air valve ( which gives extra air for starting and warmup) draws it's air from the left side, and then feeds the right through the balance pipe at the rear. The right side filter is really only drawing air when the engine speed is off idle.

 

The vanes on the air pump are carbon and they wear, thus small bits of carbon in the air it pumps out. I think ( going from memory) the hose goes to a diverter valve, and from there can go to the exhaust.

 

I didn't notice any greater dirt on the left than the right, though there might be. The right had those black bits, which made it look pretty bad. So it's vane carbon, eh? Good to know that the paper isn't getting singed, anyway.

I noticed when I started her up today, for the first time in a week, the RH pipe was going putt-putt-putt while the LH one was purring. I checked again when I got to my destination and they were both the same (so I don't think it's a misfire), so I wonder if that's to do with the LH air system working harder at startup/idle...?

 

Hi Someday

Same here, the instruction on those Air Filters is nothing but mega confusing.

When it says 'Front' does it meant that where it says 'Front' should go at the 'Front' or just point to the 'Front'?

I figured it out some time ago that the Metal part should be over the place where it sucks Air, to prevent any loose Cardboard being sucked into the Engine.

And I'm sure that we are not the only ones who's heads were spinning over that.

 

Ha, yeah! My first thought was that that was the front, but then the arrow would make no sense. At least I think it would make no sense.....
I suspect Lady Mary's PO (or the garage, actually) got confused too. Perhaps they decided to put both in different ways because one was bound to be right....
Or maybe they were just sloppy and didn't pay much attention....
I really do like my ellipses, don't I?

 

that's the first time I've heard this. How can the motor get enough air thru only one air intake and a restricted one at that?

Also, what it the purpose and importance of the small diameter "Y" shaped pipe connecting both intake manifolds?

 

if you mean what I think you mean, it is part of the crankcase breather system.
greg

 

Little correction here: Marelli makes the ignition Lucas the injection

 

That's at idle the air is only supplied off the left side. Once the throttle is opened, the right side throttle plate opens and it draws air from the right side filter.

To be pedantic, at idle there is still the 0.002" throttle plate clearance so some air is drawn from the right side filter and through the right side throttle plate, but the majority of the air is supplied through the AAV, with breathes though the left filter.

 

Seems to be nature of the beast. After mine has been sitting for the winter it runs terribly and then smooths out as it warms up. Sticky injector maybe? I don't know. Always seems to go away after a lumpy cold idle.

 

The AAV feeds air into the and of the B bank manifold plenum directly by the 1 inch crosspipe manifold balance pipe where it joins the B bank plenum at the rear of the heads. The plenums are inside the butterflies, so both sides get air directly from the AAV via the crosspipe in A bank's case. Air is not significantly preferentially fed into one bank by the AAV.
Greg

 

Oops. Yes, the PDF does say "ignition".

 

She'd been sitting in the cold, undriven, for seven days so that was a fairly long time between drives. And the engine did run smoothly, so I wasn't too worried.

 

Is it necessary or can the pipe be removed and the ports plugged safely?

Sounds like pulling a spare AAV from one of the junk yard cars is a good idea.

Too cold today to pull the windshield. Will wait for warmer weather to reduce risk of cracking. Did get a mirror, both door sills - the stainless steel style (nice upgrade over my '87 grey plastic style), a power antenna, and a temperature control panel with fiber optic lines.

 

Hi Brad

Even if you don't use it, its worth pulling another AAV as a Spare, I very much doubt if the Junk Yard knows how valuable it is and would also grab both FPR's while you are about it.

You can sell the 'A' Bank FPR (The most expensive one £65) (UK) as its not needed but not a lot of people know that.

But keep the 'B' Bank FPR (The Cheap one £45) as if yours packs up as mine did, then your Car won't Start.



Also pull the FPR on 'B' Bank to keep as a Spare, the one by the Red Oil Filler Cap, as you know.