bigolddeerhunter said:
I changed my air filter on my 2005 Jetta yesterday. I noticed that one side of the white pre-filter was dirty and the other side was completely white. The side toward the engine was dirty and the side toward the inside fender was white. My replacement filter did not have a white pre-filter. From reading some of the post I understand that is a winter filter. I live in the sub tropics of the Texas Gulf Coast. I don't think we are going to have any freezing weather for at least a few more years....perhaps the next ice age. Do I really need to be concerned if there is a white pre-filter on my replacement? Also why is only half the fllter getting dirty?
The PD air boxes are designed differently from the older model TDIs. The filter box is partitioned so only about 2/3 to 1/2 of the air filter filters air for the engine. The other part of the filter is blocked off by a wall in the air box. Who knows why VW engineering did this.
If the air filter or snow screen (yes, I found--and removed-- a snow screen in my PD air intake) becomes plugged, a spring-loaded flap on the secondary air intake (a snorkel that points towards the engine, under the hood) opens and allows the unused (boxed off part) of the filter to filter the air.
Perhaps this is set up like this to prevent the filter from tearing open and dumping dirt into the engine if it gets blocked. Only a guess though.
Now about the filter with the white mesh on it. My car came with one from the factory and the air box has a stamping on it indicating that is the correct replacement filter. Its about $15 more than the the other filter.
My thoughts are to use this new filter if you do not have a snow screen and use the older style (without the white mesh) if you have a snow screen in the intake snorkel.
Odd, but my car had BOTH the snow screen and the new type filter.
--Nate