Dust in clean side of airbox

[twX]

I recently opened the airbox on my Subaru to inspect the filter, and I noticed a concerning amount of dust in the clean side of the airbox. Photo:

The car has 50,000 miles on it, that is on it's third air filter. I've never cleaned out the airbox before. The previous two air filters were AC Delco filters, or so I thought. I looked at the filter I removed, as well as the new AC Delco filter I just purchased from Amazon, and they're both marked as Lubefiner AF3984. I assume that these are not legit AC Delco filters. In any case, these filters are about 5mm shorter in height than the OEM Subaru Denso filter I just picked up. The plastic frame is less rigid, and doesn't completely run straight on any side, showing as much as a 1mm gap under my straight edge. Looking at the depressions in the fabric seal on the perimeter of the filter, it seems like it was pressed against the airbox on each side, but on one side only by about a millimeter. The fabric seal is discolored in a couple of places, especially one of the bottom corners. Here's a photo of the clean side of the filter:

I'm not sure exactly what to make of all this, but I'm assuming that the air filter wasn't sealed well. I've cleaned out the airbox and installed a new OEM filter. I'm going to change the oil and oil filter right away as well. The engine hasn't used a drop of oil in the past 5000 miles, so I'll consider that to be a good sign. I plan to check the condition of the airbox once in a while to see if it is still an issue.

I'm not a fan of the design of the airbox on this car. It has a hinge on the bottom, and fasteners only on the top side, to tighten the two sides of the airbox to the air filter. The filter frame as well as the part of the airbox it rests on are both hard plastic, with just a thin piece of fabric on the filter to help seal it. I might consider using some grease around the edges of the filter. Any suggestions?

 

[SC Maintenance]

Most airboxes I have seen are designed such that if you get the filter in correctly the vacuum from the engine pulls it tight to seal, so I assume it is either defective or installed wrong.

I wouldn't use grease, it will dirty up either your MAF sensor or TB or both. If its not sealing try a different brand filter - or just go get an OEM filter - at least it will fit.

I have had dealers screw up the air filter install while checking them on all my vehicles - why I only go to the dealer while under warranty and still check everything before I drive away, but its fairly easy to do if you don't pay attention.

 

[oggb]

If this is a turbo Subaru you should take the intercooler off and wash it out as well.

 

[BHopkins]

Interesting that you just shared this. I just changed the engine air filter on my wife's Outback as part of the 150k mile service. I also inspected the "clean side" of the air box, and did not note any dirt. I have always installed a NAPA Gold FIL 9012.

 

[Bjornviken]

I recently opened the airbox on my Subaru to inspect the filter, and I noticed a concerning amount of dust in the clean side of the airbox. Photo:

View attachment 115020

The car has 50,000 miles on it, that is on it's third air filter. I've never cleaned out the airbox before. The previous two air filters were AC Delco filters, or so I thought. I looked at the filter I removed, as well as the new AC Delco filter I just purchased from Amazon, and they're both marked as Lubefiner AF3984. I assume that these are not legit AC Delco filters. In any case, these filters are about 5mm shorter in height than the OEM Subaru Denso filter I just picked up. The plastic frame is less rigid, and doesn't completely run straight on any side, showing as much as a 1mm gap under my straight edge. Looking at the depressions in the fabric seal on the perimeter of the filter, it seems like it was pressed against the airbox on each side, but on one side only by about a millimeter. The fabric seal is discolored in a couple of places, especially one of the bottom corners. Here's a photo of the clean side of the filter:

View attachment 115030

I'm not sure exactly what to make of all this, but I'm assuming that the air filter wasn't sealed well. I've cleaned out the airbox and installed a new OEM filter. I'm going to change the oil and oil filter right away as well. The engine hasn't used a drop of oil in the past 5000 miles, so I'll consider that to be a good sign. I plan to check the condition of the airbox once in a while to see if it is still an issue.

I'm not a fan of the design of the airbox on this car. It has a hinge on the bottom, and fasteners only on the top side, to tighten the two sides of the airbox to the air filter. The filter frame as well as the part of the airbox it rests on are both hard plastic, with just a thin piece of fabric on the filter to help seal it. I might consider using some grease around the edges of the filter. Any suggestions?

looks like it have been leaking dirty air true the botton right corner

 

[ZeeOSix]

Was the pile of dirt in the red circle inside the clean area too?

 

[twX]

Was the pile of dirt in the red circle inside the clean area too?

No, that was brushed out of the dirty side of the airbox. I've since cleaned that up. A lot of plant and insect debris builds up at the base of the air filter and gets crammed into the pleats. I just installed an insect screen on the intake to address this. Photo

looks like it have been leaking dirty air true the botton right corner

Yeah, unfortunately that's the corner that's at the bottom of the airbox against the edge of the engine bay and it's difficult to see or feel how tight the airbox might be on that corner. I was thinking of installing clamps on the two lower corners of the airbox in case the bottom fits a bit loose, since there is only a hinge along the bottom and tightening clamps up top. I think I'd have to be careful that they're not so tight that they warp the airbox and cause poor sealing elsewhere. I'll probably use the new filter for a while first to see if I still have issues.

 

[Androideka]

No, that was brushed out of the dirty side of the airbox. I've since cleaned that up. A lot of plant and insect debris builds up at the base of the air filter and gets crammed into the pleats. I just installed an insect screen on the intake to address this. Photo



Yeah, unfortunately that's the corner that's at the bottom of the airbox against the edge of the engine bay and it's difficult to see or feel how tight the airbox might be on that corner. I was thinking of installing clamps on the two lower corners of the airbox in case the bottom fits a bit loose, since there is only a hinge along the bottom and tightening clamps up top. I think I'd have to be careful that they're not so tight that they warp the airbox and cause poor sealing elsewhere. I'll probably use the new filter for a while first to see if I still have issues.

My Camaro has an absolutely terribly designed airbox where the two plastic clips that hold the side away from the TB tube are prone to breaking off, which I noticed when I replaced my air filter. No telling how long I was sucking in bad air (and I live in Phoenix, AZ). Haven't had any problems. Anyways, because the new airbox was on backorder everywhere, I used aluminum tape where the upper and lower airbox parts meet for a few months. I thought about a clamp but didn't want it bouncing loose and into something important. With the aluminum tape, I never got dirt buildup like I had after the tabs broke

 

[FreedomOne]

Could be a warped air box.

 

[MParr]

Is the lower air box something other than a molded one piece unit?