I recently purchased a 2004 Bonneville. Under the hood on the passenger side is a compartment labled "filtration". However there is no filter in it. It'* just an empty compartment but you can see down inside of it all the way to the blower. Should there be a filter in this? The dealer says no. But it sure looks like there should be. If a filter goes in there, can you get it at any parts store or is it a dealer item only?

Welcome. First things first... The search function works great. Just run a search with the criteria being cabin AND filter and specify the 2000 and Newer section.

Here are the ones that should cover your questions completely:
http://www.bonnevilleclub.com/forum/...ic.php?t=30051
http://www.bonnevilleclub.com/forum/...ic.php?t=14537
http://www.bonnevilleclub.com/forum/...ic.php?t=13593

Good luck

welcome Bob,
you can pick up a filter at any parts store.

I am going to reply on this one even though I started the other thread. I just ordered the cabin filter assembly 25669930 from GM as I stated in my earlier thread. Since there wasn't a Fram assembly locally and I needed parts from gmpartsdirect anyhow, I just went that route.

It showed up as what sounds like, the same assembly as if you bought the Fram (except I hear the Fram assembly has the anti-odor carbon filter. This GM unit does not contain the retainer clip, so I guess I am going to improvise for now.

In the meantime, I haven't figured out how to put the assembly in that hole. Fixin to re-read the other posts.. The right side won't go through the hole. Hum...

Done! You have to hold your tongue right to get the right side to clear. It popped in after a little persuasion.

Anyhow, don't need the retainer clip. In fact, without the retainer clip and using a small tie strap, you are able to push the filter a little more down into the hole. Seems like it would seal it off better.

I HAVE PICS. Reply or PM me and I'll send them. Wish this forum could host photo'*.. Oh well.

That new filter will make a huge difference to your cabin air. A bad/non existing filter will make your cabin air 7 times more polluted than the outside air.

They recommend every 10,000 or so miles to change it, but once a year is not a bad way to think instead of worrying about mile amounts, lol.

i change mine everytime i change my motor oil...4-5K that way i know i have clean fresh air cuz i dont think i would want to wait a year to change it... its pretty dirty at 4k helps with my allergy'* so i dont looke like this ->

Mine came original with a filter and I have changed it once at 20,000 km. Dealer cost is $50 Cdn. It is carbon impregnated. Hepa type.
Very pricey but it keeps everything clean inside with no dust on the dash or in the air.

Indeed. With allergies, you gotta play it by the way you feel/react to the interior air. Those carbon activated ones(that 2000silverbullet mentioned) are much better than my paper one, but since noone has allergies in my immediate family, I just use the regular ones.