Why is air filter only half dirty?

Joined
Jan 21, 2006
Location
Texas Gulf Coast
TDI
2005 Jetta
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?
 

tditom

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Sep 5, 2001
Location
Jackson, MI
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formerly: 2001 Golf GL, '97 Passat (RIP) '98 NB, '05 B5 sedan
some people see the filter half-dirty, some see it half-clean. Its all in your perspective.:D

Probably this is where the air intake is on the other side of the filter. I dunno if you really need the pre-filter living down there.
 

katipo

Veteran Member
Joined
Mar 22, 2004
Location
Texas Panhandle
there is a side of airbox that is for times when you get a blocked air intake from perhaps snow. A little gate pointed out of airbox to left allows air to enter...this part will have that little three or four inch margin of airfilter for it.
 

dave333

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Sep 3, 2005
Location
SE US
TDI
Did own... None right now!
I saw the same thing on my '06 Golf. I gently banged out the dirt and then rotated the filter 180 degrees and put the dirtiest end where the cleanest end was.

I just had my airbox off and at 13000 miles decided it was time to put a new clean one in there. N. Florida sure is dusty and dirty!!!

Anyway, is there some reason, any reason why we don't open up the entire filter area? My dremel would make quick work on that divider and some duct tape would certainly keep the emergency door closed. What's the group consensus on doing something like that?
 

TornadoRed

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bigolddeerhunter said:
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?
For some reason I have one extra "cold weather" air filter and three "regular" air filters. (I guess I am all set for a long, long time.)

I don't see anything wrong with the regular air filters. The ones with the white foam pre-filter may be slightly better, if you ever drive through some deep water -- the filter will hold together better while the regular filter might tear open if it gets damp.

But if you ever drive through water deep enough to kill the engine, even if you can restart the engine I'd recommend replacing the air filter ASAP.
 
Joined
Jan 21, 2006
Location
Texas Gulf Coast
TDI
2005 Jetta
A follow up question. Is there any problem with VW because I used a Fram air filter from Wally World? I hate to think what they charge for an air filter with the white pre-filter. I didn't measure but will the non pre-filter become dirty on one side like the pre-filter type? ...or....Is the Fram filter going to allow the whole surface of the filter to be used? Seems sort of a waste that the filter is not even dirty on the largest part. It looks like an unused filter over on that side. I forgot to say I have 32K on the Jetta.

Thanks for the info. I have learned a lot from just reading this site for a year.
Oh one funny note....the kid that changes my oil at the stealership came unglued when I said to him that I would see him in 10K miles. He said 5K....then I said no 10K acording to the book. They don't even know about the mileage intervals. I found it somewhat odd that each time I get an oilchange they have to re-write the sticker to read 10K for the next change. I wonder how many folks get taken by this? I had the fuel filter changed at 30K. At 20K the filter would have only filtered about 500 gallons of fuel. It is a large filter and that is not a lot of fuel for a filter of that size. I also buy my fuel at stations that sell a lot of fuel so it is fresh. I carry an extra filter with me in the trunk just incase I get stuck out in the boondocks with a dirty filter. Wow those filters are expensive. It would be nice if they had a system like on my PSD.
 

tditom

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Jackson, MI
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formerly: 2001 Golf GL, '97 Passat (RIP) '98 NB, '05 B5 sedan
b.o.d.h.-
what oil is the dealership putting in? Is it the VW505.01?
 

PDJetta

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Location
Northern Virginia
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'04 Jetta GLS TDI Pumpe Duce Platinum Grey w/ Leather
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
 

Drivbiwire

Zehntes Jahr der Veteran
Joined
Oct 13, 1998
Location
Boise, Idaho
TDI
2013 Passat TDI, Newmar Ventana 8.3L ISC 3945, 2016 E250 BT, 2000 Jetta TDI
Reinstalling an air filter after the box has been opened is allowing dirt to migrate AROUND the now damage filter seal! When you come crying that your MAF sensor is dead don't shed any tears here.

Leave your air filter installed until 40,000 miles, don't look at it, don't mess with it LEAVE IT THE HECK ALONE!

Everytime the filter is removed or opened IT MUST BE REPLACED with a new OEM filter.

OEM air filters have a 5-10 micron rating. Aftermarket filters seldom have better than 20 micron ratings. MAF contamination is a big factor in designing OEM air filters.

If you absolutely have to know how the filter is doing install a manometer from your local CAT dealer aka filter restriction meter and replace at 25" WC of restriction. This translates into around 60,000-80,000 miles on the OEM filter.

The fact is the more you guys mess with these cars the more you F\/C|< them up. Leave your poor cars alone, STOP slapping around the filter and visual inspection of the air filter is ABSOLUTELY no indicator of filter condition!

DB
 

tditom

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formerly: 2001 Golf GL, '97 Passat (RIP) '98 NB, '05 B5 sedan
DB-
So everytime we take off the air cleaner housing to clean the bugs out of the snow screen we should replace the element? The perimeter seal certainly LOOKS robust enough to seal sufficiently again. TIA
 

pepper10

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tditom said:
DB-
So everytime we take off the air cleaner housing to clean the bugs out of the snow screen we should replace the element? The perimeter seal certainly LOOKS robust enough to seal sufficiently again. TIA
Do you need to remove the filter to clean the snow screen? On the ALH engine, you just remove the airbox. No need to open it as the snorkel simply slides into the airbox.

DB, the seal on the filters should be flexible enough for repeat applications as long as it has not dried up from old age... Can you please explain in greater detail your reasoning on this single seal crush?
 

tditom

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formerly: 2001 Golf GL, '97 Passat (RIP) '98 NB, '05 B5 sedan
pepper10-
But you can't get the snorkel out unless you free the airbox housing from the fender in my Golf. The securing nut is inside the airbox.
 
Joined
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Location
Texas Gulf Coast
TDI
2005 Jetta
tditom said:
b.o.d.h.-
what oil is the dealership putting in? Is it the VW505.01?
Yes it is the Castrol from Europe. I have seen them put it in. They are using the right stuff.

Gee from reading the different responses...should I put the old one back in and just turn it around? Both filters have a flex seal and did not appear that it would leak if I put it back in.
 
Joined
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2005 Jetta
Drivbiwire said:
The fact is the more you guys mess with these cars the more you F\/C|< them up. Leave your poor cars alone, STOP slapping around the filter and visual inspection of the air filter is ABSOLUTELY no indicator of filter condition!

DB
I didn't know that. Then what is the stuff and why wouldn't visual inspection tell you it is dirty? I am not trying to dispute you, I just don't understand why it would not be an indicator.
 

TornadoRed

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Not yet mentioned, surprisingly, is that an air filter has to be really, really dirty before it can begin to negatively impact engine performance.

The replacement schedule is every 40k miles.
 

pepper10

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bigolddeerhunter said:
I didn't know that. Then what is the stuff and why wouldn't visual inspection tell you it is dirty? I am not trying to dispute you, I just don't understand why it would not be an indicator.
Color is no indicator of restriction. Not all dust is black for instance. The only measure of a filter's condition is restriction unless the media is compromised (torn) where you should replace it anyway. A good example is the water filters on refrigerators. Manufacturers will tell you to replace them every 3 months. I will tell you to change it when the flow of water is severely reduced. The fact that flow slows down it indicative of the filter doing it's job. As for the flow restriction indicator, lookup www.Filterminder.com . Get the 25in'hg unit non-screw type. $10! You simply drill a hole in the airbox cover above the filter on one of the sides, insert the included rubber grommet and pop the filter on place.

tditom said:
pepper10-
But you can't get the snorkel out unless you free the airbox housing from the fender in my Golf. The securing nut is inside the airbox.
The you are screwed according to DB. This is not a problem with the ALH engine. The airbox is held in place by 2 bolts fore and aft of the box, not inside of it. I still don't understand his rationale in regards to seal integrity...:confused:
 

tditom

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pepper10 said:
The you are screwed according to DB. This is not a problem with the ALH engine. The airbox is held in place by 2 bolts fore and aft of the box, not inside of it. I still don't understand his rationale in regards to seal integrity...:confused:
Maybe I'm mistaken. My daughter has my Golf (ALH) at school right now, so I can't check it, but I thought I needed to pull the airbox out to get to the snow screen. Maybe what I'm remembering is the nut holding the snorkel to the fender. Do you need to remove the battery if you don't pull the top off the airbox to get to this?
 

pepper10

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tditom said:
Maybe I'm mistaken. My daughter has my Golf (ALH) at school right now, so I can't check it, but I thought I needed to pull the airbox out to get to the snow screen. Maybe what I'm remembering is the nut holding the snorkel to the fender. Do you need to remove the battery if you don't pull the top off the airbox to get to this?
On the ALH, to remove the airbox, you remove the 2 vertical nust holding it in place, remove the clamp and hose that brings the air from the box to the engine, disconnect the vaccum tube from the box under the big hose, disconnect the MAF and just pull the box out by swivelling it towards the engine. The snorkel is attached to the fender by one nut. Take it out and pull the snorkel towards the windshield for removal.
 

tditom

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Very good description! I'll get to check it this weekend when she's home. Thanks!
 
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Pepper...very informative site. I have a device like that on my Ford PSD. It came with it from Ford. I guess I should put the old filter back in and just drive it. Does anyone else have any advice as to this device and the use of it as it relates to the VW warranty?
 

jkeller

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I agree with DB. Leave it alone. I heard somewhere once that you let more dirt into your engine changing the air filter than the whole time between changes.

If you must look at the filter, be sure you have a shop vac and some wet rags around and carefully clean the inside of the filter box.

There is absolutely no way I would rotate and reinstall, or clean and reinstall, a dirty filter. How much do they cost compared to the cost of your engine?
 

pepper10

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tditom said:
Very good description! I'll get to check it this weekend when she's home. Thanks!
Tom, just be careful while pulling the vaccum hose off. It has a tendency to stick. You don't want to break the plastic fitting on the airbox...:eek: I used a flat screwdriver by putting it between the hose and the airbox and tisting it to loosen the hose. Have fun!:cool:
 
Joined
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2005 Jetta
Hummm....now I am getting paranoid.....

What does the TDI engine have that my PSD doesn't have that would prevent me from using a non-pre-filter like on the Ford?

Why would VW make a winter filter for me to use in a sub tropic environment? Folks I have banana trees and citrus growing in my neighborhood.
 

mparker326

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pepper10 said:
On the ALH, to remove the airbox, you remove the 2 vertical nust holding it in place, remove the clamp and hose that brings the air from the box to the engine, disconnect the vaccum tube from the box under the big hose, disconnect the MAF and just pull the box out by swivelling it towards the engine. The snorkel is attached to the fender by one nut. Take it out and pull the snorkel towards the windshield for removal.
I always just leave the clamp and hose/vacuum tube attached and just lift it up to get at the one nut. The less I take off, the less I lose/break.
 

Drivbiwire

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Foam rubber once heated loses it's original shape and the ability to return back to it's original form this is also called "memory". Once you clamp the filter into the airbox the seal is compressed. The airbox once the engine shuts off heats up and thus heats the seal on the filter. The filter will remain in contact provided the airbox is not opened. If the airbox is opened the filter will NOT apply the original amount of pressure against the two halves. The engine will pull air and dust through any portion of the seal that is not making firm contact with the two halves. Fact is the leakage ALWAYS occurs on the engine side since this is the side with the most suction.

Open your filter and look at the top of the filter element. ANY dark tracking or dirt is an indtication you have caused a filter seal failure.

On my filters I will apply a very very thin layer of O2 sensor safe sealant on the engine side of the element. This prevents any tracking and allows me to open the box to clean the snow screen in my A3 (located at the bottom of the airbox) WITHOUT breaking the seal of the filter. My manometer will read 15" wc when the snow screen is plugged or if it has tripped open at some point.

For the ALH motors you do NOT need to open the box. Remove the two hold down bolts as already suggested and move the entire assembly to the side. The screen is easily reached with a single 10mm nut holding it in place.

The cold climate filters allow you to have TWO filtering surfaces regardless of your climate. The first filters out coarse dirt and debris and also acts as a stop for ice crystals or for that matter water...to a point provided you did not submerge the car. The primary element will stop the fine particles down to 5-10 microns.

The massive surface area of the TDI filters dwarfs anything out there and outflows the K&N or other aftermarket filters as a function of greater total surface area WITHOUT sacrificing filtering capability..

DB
 

PoochiePD

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Sun Prairie, WI
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2013 Tempest Blue Jetta
Funny thing about this thread...

I just changed my engine air filter and cabin filter today at 45,000 miles...I know, I know, 5,000 miles late.
Anyway they both LOOKED really clogged up and they really were after comparing performance of my engine and performance of the blower fan to the old ones.:eek:
My vents blow out air better than ever and, most importantly, I gained a LOT of top end power back. Too bad I didn't know about this sooner...And btw one side of the engine filter was definitely dirtier than the other, but the dirt kinda faded as it went to the other side.
 

pepper10

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Because the air gets sucked into the engine from only one side of the airbox, it is normal for the filter to get dirtyer on one side. Simple physics: vaccum will be higher on the engine side and will allow for a higher pressure drop then on the fender side, thus more air will flow through the filter closer to the intake duct. As the filter gets dirtier in the path of lower pressure, the air will start to flow around the dirty section of the filter following a new path of lower pressure. I am no physicist but I think I got it right.
 
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