Gen III Prius Cabin Filter Replacement

...and they don't really filter that much anyway, otherwise we would be changing them a lot more.

 

Dust accumulates pretty fast on my dash area so I'm sure you are right. Even when the filter is new.

 

Not exactly. The direction of air flow through a centrifugal fan is always in axially and out tangentially or radially. The fan is immediately below the filter with its axis vertical. You can easily spin it with your fingers by reaching into the filter opening when the filter is out.

I agree with the rest of your post.

 

Depending on which way the fan spins couldn't it be pushing OR pulling air?

(Excuse caps, typing on a bitty phone, hard to do italic)

 

i think cr94 knows a lot more about fans than most of us. i always have to look at the position of the blades and direction of spin to figure out if my ceiling fans are blowing up or down.

 

I am also puzzled about how the filter is supposed to be installed. Since I did not have the benefit of observing the original filter element placement directly from the factory (new vehicle), I am left to decipher it from the fittings at hand. Referencing the Owner’s Manual it does not show a diagram of the replacement operation. It does say on page 288 to refer to the "Owner’s Manual Supplement / Scheduled Maintenance Guide" which was not in the reference material I received with vehicle purchase. I checked the Toyota Ownership Website for the supplement and found a 66 page Warranty and Maintenance Guide. This must not be what I am looking for since it only describes scheduled maintenance intervals and such. No diagram.
Several days after I purchased the vehicle I had removed the existing cabin filter to check for cleanliness. The filter was just jammed in there and was obviously not installed correctly in the air path. Looking over the filter element, there are two stiffeners on either side that are perpendicular to the filter element pleats. It is on one of these stiffeners that the word UP and an arrow can be found. This is the OEM Toyota filter I’m talking about. Looking inside the filter housing, just above the fan I noticed that there is a slot on the right side that could accommodate and contain a stiffener. But when the element is inserted with stiffeners on the sides in this fashion, the rear pleats catch on a framing protrusion over the fan inlet. There is also quite a bit of space between the front filter pleat and the access door, allowing unfiltered air to pass. If the filter element is inserted with a stiffener in the back and the UP/arrow marked stiffener up front, it fits the opening properly and is held tightly to the top of the filter housing when the access door is replaced. So this must be the proper method of installation.
It might also be interesting to note that I just had my dealer do a 60,000 mile service on the vehicle, and replacement of the cabin filter was on the list. When I checked the filter orientation this morning it was properly inserted as described above.

 

it doesn't make sense to me that the stiffeners are from and back. whats the point, to have something to press?

 

That's indeed true of axial-flow (propeller-style, as in bisco's ceiling fan example) fans. In centrifugal fans and pumps, the fluid enters at the center, more or less in line with the axis of rotation, takes a 90° turn, and exits from the outer ends of the blades.

 

Evidently so. My impression when I peeked at mine is that the filter and its housing might provide reasonable sealing against air bypassing around the front and back edges, but not on the sides, especially not on the right side. If 5% of incoming air sneaks past the filter that way, that's still 95% better filtering than I had in any previous car.

 

the fram i bought at auto zone was so flimsy, when i started to push it in, the sides buckled and the leading edge wouldn't go all the way in. the oem is much stiffer all the way around.

 

That is what I noticed also. The OEM is much stiffer and washable too. Regarding the filter fit, there are some small guide tabs on the back of the removable access door that serve to locate the stiffener of the filter element upward. This presses the filter element against the top of the filter box. The left and right sides of the element are still just flexible pleats, but there appears to be enough overlap of the filter box to effectively seal the opening. Maybe 5% blow-by or less depending on how clean the filter is and the velocity of the intake air. Now I think I'll put it all back together and relax the crick in my neck.

 

i suppose it's more about filtering the large stuff. what happens when you push the pollen button?

 

That is a button I have yet to press. I read about it though, switches to recirculate at, I believe, a medium speed for like 3 minutes. Then switches off. It doesn't do any microscopic scrubbing or electrostatic separation like I would want it to.