There are already a few good posts on the forum on this subject which were very helpful to me.
My post here is just to give another angle on the job and to help those who have not done it yet and are a bit hesitant to change their T31 pollen filter.

I replaced my pollen filter yesterday evening and after reading all of the help already posted on this forum, I need not have worried as it was easier than expected.

Despite the Nissan Workshop Manual indicating that the glovebox should be removed first, I did not remove the glovebox as I didn't see any advantage to be gained by its removal only adding to the likelihood of breaking something or losing screws etc. It does NOT gain you significantly more access as you still have to reach into a tight space regardless. There is an air duct and other items in the way which require the filter to be squeezed out of shape (its designed to withstand this) to get it in and out even with glovebox removed. Also it would needlessly add time to what is one of the more simple jobs I have done on my X-Trail. You will largely be doing the job by feel in any case.

For those that have done things like changing brake pads, other brake caliper overhaul work, replacing small mechanical parts, working in the tight space around an engine etc, you will find changing the T31 pollen filter very easy in comparison. But like anything with cars, you generally need to fiddle somewhat. With the pollen filter you are working in an area that you cannot easily see so you are largely going by feel. The design of its access and fitting despite its location is not actually that bad, once you have done it once you should have no fear doing it again in the future.

Here's views of the location with filter cover on, then off. Yes, this is WITHOUT taking off the glovebox. It's in clear view!



The filter cover is very easy to remove. It is made from flexible plastic. Just pull the bottom extension downwards to unclip it then it should easily release from the top clip. See where the clips are in this photo so you will know what you are doing. The bottom extension is quite bendy. Don't worry, you will not break it!



Also the filter itself is fully flexible in three dimensions and can be twisted. It will spring back to original shape. With that in mind, you can be quite rough removing the old one. It does fit quite neatly in its slot so you will need to push the visible side inwards to deform it so that you can try to grip the lower corner. Use a flat end screwdriver or other tool if you really need to however I was able to remove mine without any tools at all other than my fingers. Just fiddle with it until you can pull it out. Get a vacuum cleaner with a narrow nozzle to clean up all the small leaves, dust, fluff, feathers and dandelion seeds etc that will likely be there!

Putting the new filter in is also a little bit fiddly. See photos below. You can squeeze it and twist it to get it up in there. Then feed it into the slot by feel. Try to get the lower corner in first, then squeeze it and using feel, feed the top corner in. Again, don't worry too much about bending or twisting it a little. You will notice that once in its tight slot, it quickly springs back into shape. You will see from my photo above that it expands out again to perfectly fill the slot. On the edge which you should keep outwards, there is an arrow to show airflow direction. It is near the top on mine so out of view in my photo. If you keep the writing edge the right way up so you can read it like in my photos, then it is fitted correctly.



Putting the plastic cover back in place is very easy. Fit top edge first then push the bottom into position until it clips securely. The design and fit is logical and you will know when it is correctly in place.

Go on - you can do it!

Let me know if this helps anyone who would otherwise not have tried it.

Here's another photo of the pollen filter moving into position.