[john76]

My car is now out of warranty so I've started doing my own servicing.

Changed the pollen filter earlier, I copied the airflow direction arrow on the new one with the one that I took out, fitted by Cotswold BMW in Cheltenham at the last service, as you would.

Then in the garage I noticed that the filter was full of crap on the wrong side of the filter. The bits of rubbish and leaves etc shouldn't be on the side that the arrow points to.

The arrow on the filter fitted by Cotswold was pointing *in* to the car when I pulled it out, clearly the wrong way round.

So, the correct way round is for the arrow to point towards the engine.

The little leaflet you get with the MANN filter agrees with this too, as do Bentley in their youtube video.

The good news is I can now constantly bore the wife with, "see, this is why you do your own servicing". The bad news for anyone else getting their car serviced by the main dealer (maybe just Cotswold, who knows) is that it might be wrong. Granted it's probably not the end of the world, but if they get this wrong what else is wrong!

[M140_BCS]

Must have been installed by the apprentice technician…

Probably can't tell left from right so correct airflow direction will take a few years to grasp…

[Eddamoo]

Interesting! I've always installed them from front to back. Never actually looked at the side the muck was on. Will make sure I do next time!!

[jamiem1987]

Can anyone confirm for definite? I’m going to buy another if the original post is correct as mines in the wrong way also, noticed poor blower performance

[john76]

MANN, Bentley (see below) and my findings with which side the leaves and crud appear on all tally up with the fact that the filter should point to the front of the car.

[Eliginator]

Hi john76, as you're based in the UK i'm assuming you have a RHD car? If so, can you fill me in where the cabin filter is located as all the videos I've found, show it being replaced on LHD cars.

Is it still on the right hand side of the car and in the drivers footwell or on our passenger side?

[bishbosh]

It's on the passenger side.

[john76]

Indeed, it's the passenger side (i.e. the left hand side as you sit in it). The replacement of it is the same as LHD cars, only on a different side of the car.

[Eliginator]

Thanks bishbosh and john76. That should be easy to fix. Unlike an old Volvo I had, they didn’t change it for UK market and you couldn’t get it out due to the pedal box! Was a right pain. Hopefully this one not so much.

[Bigfish786]

Hi.
I'm going to be fitting mine in the next few weeks.
I was just going to follow the arrows on the old filter, and put mine in the same way. You would think the air flow would be from the engine into the cab, but you are saying it's the opposite direction?
Just wanted to make sure I got it right first time.

[john76]

Indeed, the arrows point to the front of the car.

You'll be able to tell the correct way when you inspect the filter. There will be crud and bits of leaves on one side and nothing on the other. The air flows from the cruddy side to the other.

[johnung]

Originally Posted by john76

Indeed, the arrows point to the front of the car.

You'll be able to tell the correct way when you inspect the filter. There will be crud and bits of leaves on one side and nothing on the other. The air flows from the cruddy side to the other.

Interestingly, I once talked to a dealer tech who said that this is a confusing subject. He said that he has worked on many cars where he was replacing the factory installed cabin air filter and found them installed in both directions right from the factory

[john76]

I guess ultimately it won't really matter a great deal. Regardless of the arrow, the filter will still be doing its job, filtering the air.

I can't imagine it would be possible to notice much of a difference if it was the wrong way round!

[adamf2001]

I understand your confusion. The arrow on the filter does not represent the direction of the air flow, but the direction of the filter installation. The filter should be installed with the arrow pointing towards the front of the car, because that is the direction of the air intake. The air intake is located at the front of the car, under the hood, and it draws air from the outside to the inside of the cabin. The filter is designed to trap dust, pollen, and other particles before they enter the cabin. If you install the filter with the arrow pointing towards the back of the car, you will reduce the efficiency of the filter and the air quality in the cabin. You can think of the arrow as a reminder to align the filter with the air intake. I hope this clarifies the issue for you guys!

[TurboWeasel]

Bit of an unusual thread resurrection to explain how a filter works?

[adamf2001]

🤣 just helped a friend fit his today and argued with him for nearly 20 mins about it which led me to this thread! - we found some filter brands state “Air Flow” which would mean the arrows face inwards i.e in the direction of air flow e.g Bosch, but others will have arrows pointing outwards or to the front of the car meaning “this side up” or “towards air intake” - he was changing from his OEM filter to a Bosch one which caused our “big argument” because the arrows had to be fitted the other way round so direction of “Air Flow” instead of “Air Intake” - in the end I had to eat my words because he was right 🙄 - depends on the filter brand (instructions are indeed ambiguous)!

Anyhow rant over if this helps even at least one other person from wasting time on this stupid topic then mission accomplished! 🤣

[TurboWeasel]

Ah OK, fair enough

I wonder if most of the black stuff in these filters is diesel soot and brake dust? If so, thank god for their existence! We don't want that sh1t in our lungs!

[Watsey]

Head first in the footwell, upside down, breaking my back over the passenger sill. Or maybe it’s just me.

The joys of a cabin filter change.

[TurboWeasel]

For some reason I thought the cabin filters were under the wiper cowling in the engine bay like the E90/E39 but I guess not They sound like fun to replace then, not!

I guess internal filters are less susceptible to moisture ingress and therefore mould growth? Can't think of any other reason why they would go to the expense of completely redesigning their location?

Having said that, VW/Audi cabin filters have been internal for decades. Must be merit to that method I suppose. More ££s for their replacement.