Changing Your Cabin Air Filter: Why the hell so?

 

Hey! Sports Fans! It’s been a while since the last post and today I have an exciting service to review – installing a cabin air filter in a 2024-2026 Subaru Impreza!

I mean, what could get more exciting?

Cabin Air Filter: Do I Really Need It?

No.

The idea of an air filter for a car is a bit silly, really. There are probably plenty of entry points for air other than the ventilation system, especially if you open the windows or sunroof, thus making the need for a cabin air filter pointless.

In 1989, Mercedes (of course!), introduced the cabin air filter in a response to… Wait for it! More profits.

The off-cited reason of the decrease of air quality and increase in pollution are not resolved by this system. It may reduce pollen and dust, but as it cannot be a totally closed system, and from the two vehicles I have owned, the filter and housing system does not offer an assured seal.

By 1990, the Opel Astra, a mass market car, had introduced the cabin air filter.

So, Hans Freudenburg, in a bid to prevent dust getting on his clothes while he drove, developed the idea of the cabin air filter. That must have been one hell of a long drive or one motherfracking dusty road. Was he commuting on the Dawson Highway?

Anyways, my 2013 Hyundai Accent was the first car I owned that had a cabin air filter. I never changed that filter until I had but 300,000 kms before I changed it. I really should have changed it sooner, but do you need to change it as frequently as the recommended service interval?

In the case of my Hyundai, the long time before the change found that filter had distorted and was not sitting in the housing properly, negating any filtration effects. I have no idea of how long the filter had not been doing its job, but it was a lesson in considering making changes of the filter to keep the car in good shape. I mean, you change the oil and filter but leave other items that degrade and if you have any pride in ownership, you think an owner would at least put a good filter in, or remove it altogether if you think having a cabin air filter is pointless.

Though I question the real utility of a cabin air filter, is now a part of the car’s maintenance regime and an understanding of this part and its place in the service life of your Impreza.

As to profits…

Google the OEM part number and you will find a PLETHORA of 3^rd-party providers offering solutions at a wide range of price offerings. Some are basic filters and some offer, I don’t know, protection from Anthrax or Nuclear fallout.

It’s a filter, damn it. Its primary role is to prevent PARTICULATE intrusion into the car’s cabin. It is a paper accordion pleat with a paper frame. Probably about 0.32 cents manufacturing cost. $1.01 landed cost in Canada in its box. These aren’t real numbers, but I am sure the profit margin on this part is ginormous.

Changing Your Filter

Below are the instruction for the current body style of the Impreza (2024-2026). Other Imprezas are probably similar, but CHECK your manual for correct procedures and fitment.

Replaced with FRAM CF12157 (est. $25.00 to $39.00 CDN).

 

 

Condition of Removed Filter

 

Why Change Your Filter?

It was evident from changing out the original filter it was picking up debris. Was this debris, if it passed unfiltered into the passenger cabin? Probably not, but it does prevent contamination of the ducting and fan, and that does keep the efficiency of the HVAC system intact during the life of the car.

Seriously, if you drive with your window(s) open, you are fully defeating the purpose of the filter.

Plus, for those with OCD, changing stuff related to your car’s care will be a soothing balm as each item gets done.

Do you need to change it as regularly as Subaru recommends?

Depends, Sports Fans. If you live and drive in a dusty climate or desert area, I would do the first change at the recommended interval and then amend the frequency of the changes. You could check the filter at intervals, but I think the effort outweighs the result. Plus, if you are not careful, you could introduce containments into the fan and ducting.

I would not leave it for more than 2 years, regardless of mileage, as it may start to warp and deform in the housing, preventing it from doing the job it was indented for.

Definitely do it yourself, and save some money, and learn a bit more about you car.

What Does Subaru Say?

Subaru recommends replacing your cabin air filter every 12,000 miles / 20,000 kms.

As this is a recommendation, your mileage/kilometerage may vary. If you drive on dusty road regularly, you might consider a more regular maintenance interval.

The OEM part number is 72880FN00A and its price is $30.00 USD MSRP.

There are plenty of 3^rd-party providers with Fram being one of the more recognizable brands.

Conclusion

So, a bit of contradictory information...

I think car cabin filters in most North American environments are silly. They are another high margin part that fixes a problem that does not really exist.

However, with my last car, I totally neglected the filter, and paid for it with fan noise, which potentially could have led to fan damage or failure.

My goal is to change the filter at an interval that is double that of the recommendation, and to source a filter of reasonable cost.

So, Sports Fans, take these wizened words into consideration when you consider doing a filter change.

Remember to keep the rubber on the right side of your vehicle. Drive safely and practice the Subaru Salute.

Engine Cover Install on 2024 Impreza RS: The Red Mist gets an engine bay upgrade!

 Good day Sports Fans!

Today we will gussy up the Red Mist's engine bay. As you can see it is a bit pedestrian with the intake manifold and associated hardware exposed like some Steam Punk art exbisition. The engine is left to be exposed, and even entry level Hyundias, like the Venue, have a cleaner looking engine bay.

To remedy this, I wondered if there was a solution based on the Crosstrek or other Subarus where I could fit an engine cover from another model using a similar engine. The Impreza RS comes installed with an FB25D 2.5L, and with a little research, I found this Reddit post outlining the parts they found for their 2023 Crosstrek Limited, and it was the basis for my little project.

It works, and you will need the following:

• P/N 14025AA560: Engine cover for 2019+ Forester,
• P/N 14032AA230: Rear mount brackets for intake plenum (two required),
• P/N 14032AA290: Front mount bracket for alternator,
• Two M6 x 10 mm bolts for attaching rear mount brackets to the intake plenum,

The cost, taxes in, was about $176.00 CDN, and it took 3 weeks for the parts to arrive.

The parts diagrams for Subaru are famously atrocious (one would not get away with this in aviation). Many diagrams show only the cover and do not reference or show the associated hardware.

The good new is we will walk through the process of installing the cover, step-by-step. A image will be followed with an explanation and instructions.

Engine Bay Cover Install

Parts: as outlined previously.

Tools: 10 MM open or closed wrench, blue Locktite or 3 X M6 lock washers (stainless), rags.

These are the parts you will need. I am using blue Locktite in place of lock washers, and you can see the two P/N 14032AA230: Rear mount brackets for intake plenum below the tube of Locktite, followed by the M6 bolts and the P/N 14032AA290: Front mount bracket for alternator.

The engine bay cover (upside-down view) shows the corresponding attachment points for the engine cover and the correlated attachment points. Closest to the camera are the two slots that slide into the rear mount brackets, and behind them are the two clips that attach, one to an existing mounting bracket, and the other to the installed bracket.

The engine bay before installation. Note the pulley cover to the left of the oil filter. This will be removed. Note the nutplate bosses to the right and left of the intake plenum (silver inserts in black plastic).

Close-up of nutplates in intake manifold. This is were the rear mount brackets will go.

Take one of the rear mount brackets and an M6 bolt. Place a tiny amount of blue Locktite on the threads of the bolt and install the bracket with the black plastic oriented to the front of the engine.

Note the orientation of the bracket. It is facing FORWARD with the tang to the left. This is the orientation for BOTH brackets (left and right side). Tighten the bolts (I was not able to find the torque specs), taking care NOT to overtighten. I am not sure of the material of the nutplate boss and if it is aluminu,m the bolts, which are steel, will strip the threads and then you will need to replace them. Note the tang oriented into the slot built into the intake.

Once installed, the brackets will look like this. Properly oreinted to the front of the engine. Note the tabs on both brackets fit into the plastic slots on the intake piping.

Remove the belt and pulley cover next.

Remove and retain this bolt. You will need it for the bracket you will be installing next. Note that the cover has a plastic pin (right side) that is slotted into a corresponding hole in a bracket. Remove bolt and pull gently and firmly up, releasing the plastic pin attached to the cover. Remove cover.

Access and view with the cover removed.

Close-up of the receptacle for right front plastic pin.

This is an image of the nut embossed in the body of the alternator. Note the "U" shaped receptical above the hole and the black tang on the black bracket. They mate when installed.

Reusing the bolt that held the previous belt and pulley cover, add locktite to it and position the black bracket so the tang of the bracket fits in the "U" slot on the alternator bolt boss. Tighten. But do NOT over tighten, because if you strip the bolt boss you may have to rethread the boss or get a new alternator.

Once the last bracket is installed, review your work. You should have two rear mount brackets installed and pictured, and the alternator bracket installed, with the existing bracket on the right side of the engine, by the oil filter, being ready to accept the engine bay cover.

Orient the engine bay cover with the logo and text facing the front of the engine bay and slip it into place. It goes in "flat", at a horizontal angle with a slight tip up at the front of the cover. The "feel" for the two brackets on the intake plenum is not, at first, positive, but with a bit of patience and hunting you will find it slips in and feels like there is an interference fit between the plastic ends of the bracket and the receptacles embossed in the plastic. You know you got the pins properly aligned and fitted when the forward pins that go into the rubber grommets on the forward side of the engine align. You cannt see the pin/grommet on the right, as the engine bay covers it, but you can see it on the left. With a bit of slight jostling, you will get a positive engagement.

You're now done, Sports Fans! She looks good, and with the acoustic padding on the underside of the engine bay cover, the engine runs a little quieter.

My driving impression is that engine noise is less noticeable, and I plan to test this formally in an upcoming post.

Suffice to say, I am pleased with the more finished look of the engine bay with the cover.