All the air that comes into your TDI (when the windows are up) comes through the cabin filter. Lots of air goes through the filter each day for months or years at a time. Although it does its best to filter out pollen, dirt, debris, bits of trees, and rodents, it gets tired. Although the filter replacement interval is 40K on most VWs, gurus recommend replacing the filter twice a year, in the spring and fall. It’s literally a 5 minute job, only requires a phillips head screwdriver.
Where is it?
This may be the toughest part. It’s at the base of the windshield, on the passenger side, under the plenum cover, or rain tray.
It even has its own access door, held in place with four phillips head screws.
Access & Replacement
First, peel back the gasket that seals the back of the engine compartment.
Then, loosen and remove the four screws that hold the cover in place.
Once the screws are out (the upper part of the rain tray is a good place to store them), tip the front of the cover up and lift it out of the car. Don’t pull too hard as there’s a narrow piece that fits under the cover near the hood hinge. You don’t want to break that. But move it around a bit and it’ll come out.
Then the filter is in front of you, in its holder.
You want to remove the filter in its holder, then replace the filter and put the holder back in the car. Remove the filter by pressing the tabs that lock the holder in place.
One they’re free the filter will tip up and slide right out of its base.
The filter on the right has been in the car for about 2 years (shame on us). The one on the left is new. Sometimes they’re much worse: we’ve seen mouse nests in many.
See, it does do some work. Catches leaves and twigs, too.
Take the new filter out of its box, and set it into the base. Note that there is a top and bottom, and that the direction of airflow is indicated on the cardboard sides of the filter. You can see it in the comparison of old and new filters above
Be sure to lap the ends of the filter over the end of the holder, as shown below
Once the filter is in its base, put it back in the holder by tipping the back tabs into their receivers in the base, and clicking the clips into place. You can reach around behind the filter if necessary to make sure its set in its base.
Once it’s in tip the cover back into its location, once again being careful not to force it and bend or break the plastic.