So, I got a call from a customer the other day. He had changed his airfilter(s) on his 99 Leg brighton, and now his car will not stay running. Starts, runs a few seconds, dies.

 

Well, we all know by now that this is likley a unmetered air leak (like an IAC hose or PCV hose disconnected)

 

So I arrange to go meet the guy, look at the car. And I find something I've never seen before.

 

This car has both the fender mounted airbox/filter, with the MAF bolted to it, and ALSO, the long rectangular in the housing right off throttle body.

 

I've seen the old style cars with the fender mounted, and the newer cars with the Throttle body mounted style........but never BOTH on the same car. Seemed comp[letely original too, not some hacked in setup.

 

I took a video of it.

 

 

Well, turned out the problem WAS an air leak. He had not seated the tabs on the second air filter box. ANd because this was downstream of the MAF, it acted just like an unhooked hose. Measured Gallons per second of air were 1~2 at idle. Once reconnected, and running proper, G/S were up around 4~5 at idle.

That tube is to cut down on the resonating sound of the intake.. I can't think of the proper name but it starts with an h.. just can't think of it right now.

 

Also common for leaks to happen if someone pulls the box open from that tube.

That tube is to cut down on the resonating sound of the intake.. I can't think of the proper name but it starts with an h.. just can't think of it right now.

 

Also common for leaks to happen if someone pulls the box open from that tube.

 

Yeah, the tube is common. I'm used to that.

 

This car literally has 2 airboxes, and 2 filters. Did you watch the video? You can see both airboxes in the video. The second one is right behind the engine.. It's the same box as used on the 2000+ models.

Yeah, the tube is common. I'm used to that.

 

This car literally has 2 airboxes, and 2 filters. Did you watch the video? You can see both airboxes in the video. The second one is right behind the engine.. It's the same box as used on the 2000+ models.

 

 

I did not know above was a video.. anyways now that I know what your talking about that's just a plenum.. it stores air at whatever outside pressure level is so the engine has enough air to suck down as you know the 2.5L engines suck more in then a 2.2L so that's why the box is where it's at..

 

A Plenum is nothing but a hallow box.. most if not all indoor central A/C systems have a plenum as well.

 

 

edit ok looked at the video it looks like a mix and match of parts..

 

A Plenum is nothing but a hallow box.. most if not all indoor central A/C systems have a plenum as well.

 

On the 97 and 98 models it is just a plenum.

 

BUT! this one isn't. It clips open, there is a filter in there. The car would not run because that box was not closed up right, and air was leaking at the seems.

 

Watch close again, you can see the 3 clips that hold it closed along the top.

 

This car HAS something I'd never seen before. that's why I posted it.

Many of the '99s are like that. My '99 Forester has them as well and I was also a bit shocked that it had twin intake filters. The second filter isn't terribly expensive at the dealer though so I'm not too annoyed by it.

 

Rest assured it is 100% stock. Probably a CA emissions thing. The dealer confirmed for me that it does indeed call for both filters.

 

For whatever reason the '99 Forester automatic that I have seems to have been built to go a million miles - not only does it have twin air filters but it also came stock with the turbo oil cooler.... the engine is in amazing condition for 247k. I attribute it to that oil cooler keeping the engine oil from breaking down. Really amazing what that will do for an engine - definitely putting one on all my performance builds.

 

GD

That's why I think it's a mix of parts perhaps someone with a CA emissions can chime in if they have two filter air boxes?

edit ok looked at the video it looks like a mix and match of parts..

 

Not a mi9x match.

 

All the PCV hoses fit correct, no odd bends. the boot between the boxes has the correct bend. It's all the OE setup. Just an oddball model.

 

99 Leg brighton. Phase II 2.2 CA model.

OMG 2 air filters?!?!

 

Hmmmmm, lemme see if the engine bays in my 1999 Legacy owners manual has that too.

 

If it is, I think later on in life, I should collect one of these just to brag I have 2 air filters

 

EDIT: what???

 

Edited April 7, 201115 yr by AWDfreak

The airbox on the throttle body doesn't always have a filter in it. That was where the speed density fuel injection had it's filter. The MAF fuel injection system had the filter on the fender like normal. I'm pretty sure I've opened up some of them and not found filters in there.