2004 with fuel filter in backwards for years!

Herb Goltz · Post by **Herb Goltz** » 06 Jan 2025, 12:17

After having the fuel filter rust out and leak on my 2006 this fall, I thought it would be prudent to pre-emptively replace the filter on my 2004. This weekend I tackled the job, and discovered that the existing filter had been installed in the wrong direction! It has been that way for at least as long as I have owned it (August 2020), probably longer based on how rusty it was. The only difference I can detect after installing a Mann filter in the correct orientation is a slightly smoother idle-- after 80K km it would likely benefit from some plugs, but I think I will wait until it isn't -20 with the windchill...

Post by **br0dy519** » 06 Jan 2025, 12:31

Always worried about this. The Way it's installed it almost appears backwards, but directional arrow helps.

Post by **abscate** » 07 Jan 2025, 03:56

The Kat came to me with the reversed fuel filter. It means the longer you drive the fuller your tank, as the fuel follows the arrow of course

Herb Goltz · Post by **Herb Goltz** » 07 Jan 2025, 07:25

Haha! Did you notice any changes after correcting the filter orientation? My 2004 seems to always get better mileage than the 2006-- or at least it used to

Post by **cn90** » 07 Jan 2025, 10:52

Attached is a photo of a fuel filter cut open.
Sure, one should install it correctly (fuel flows from outer diameter and converges in the center).

But you can see in this case, even if installed wrong, fuel is still filtered anyway.

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Herb Goltz · Post by **Herb Goltz** » 07 Jan 2025, 11:23

Thanks for this-- it's good to know mine wasn't completely unprotected with the backwards fuel flow! The fuel that came out of the filter after removal on my 2004 seemed very clean-- on the 2006 it was almost black when pouring out of the input side...

Post by **abscate** » 08 Jan 2025, 04:47

I cut a p80 filter open in this thread , hide the children before viewing. These filters are really overbuilt for these cars, the example above was 20 years /180k miles old

viewtopic.php?t=95661&hilit=Fuel+filter+autopsy

Post by **volvolugnut** » 08 Jan 2025, 09:39

Compared to other brands, Volvo fuel filters are HUGE!
Designed for areas of world with dirty fuel?
volvolugnut

Post by **matthew1** » 08 Jan 2025, 10:42

The worst that can happen with that fuel filter mounted backwards is sludge gets trapped in a confined area rather than a large area (center vs. exterior). And also the fine-particle trapping would happen before large-particle trapping, essentially negating the large mesh.

Shorter useful life.

Herb Goltz · Post by **Herb Goltz** » 08 Jan 2025, 11:25

Yes, they certainly are overbuilt-- I'd say there is at least 50x more filtering surface area in those than on the filter of my '69 Karmann Ghia. I suspect the typical failure modes are rusting (at least for rust belt cars) and mechanical damage, not clogging! I doubt I will ever need to replace mine again...