GM oil bath air filter

chessie4905 · October 16, 2019, 09:24:25 AM

Ok, mainly for Richard, but if you have a GMC 4108, 4905 it should interest you. Here are some pictures of it knocked down. To remove bottom pan, there are three wing nuts securing. Loosen each about two turns and swing down each. Then slightly rotate pan to release the two pin stubs that sit in two plate notches attached to the band while holding pan from dropping, as it has a few quarts of oil in it. Once the pan is off there are 3 wing nuts securing the approx. 1 1/4" thick prefilter. The prefilter is in picture 4.After removing the prefilter, you see the main filter, which is not removable and part of the assembly.
Air comes in the horizontal inlet and goes down the large center pipe into oil. It goes through the oil and passes through the pre filter, then through the primary filter and out the other horizontal pipe to the engine. Btw, the cannister is upside down in the pictures.
Another note is that the air for the filter assembly comes through the upper rh side louvers into a box with water separater. AND there is a two inch hose connection point to the coach bathroom for extracting odor. Note in second picture the dirt in pipe. This came from removing filter from body while it was upside down. Also chunks of dirt on the pre filter. There is quite a bit of crud in the bottom pan. Have no idea how long it went since servicing.here is picture of main filter. Mesh appears to be bronze. GM, in their service manual states normal service is to clean prefilter and pan, refill and reinstall. If there is excessive crud in pan or it has been quite a while, remove complete filter assembly and clean main filter. Btw, the main filter is very clean in this unit.

chessie4905 · October 16, 2019, 10:02:52 AM

Here are a couple more pics. I removed the band since I'll be cleaning, sand blasting and repainting this. I'll carefully seal interior so no debris gets into filter.Normally the band stays put.
The coach was designed to be able to remove the large filter cannister for service. You unbolt the fuel filter mounts with out disturbing the filters, and disconnect the main air line from the compressor. My engine has a large resonator attached at the blower intake. That may need removing also. Shouldn't be too difficult since the inlet and outlet filter hoses need to be disconnected anyway.

richard5933 · October 16, 2019, 10:05:12 AM

Thanks for the photos.

What's the plan for cleaning the main filter/canister?

chessie4905 · October 16, 2019, 10:08:02 AM

Clean it in my parts cleaner, then rinse with clean solvent. Seriously, it is amazingly clean. More than I ever expected.
Btw, the whole assembly has whats left of a tag. Says mfg. by Donaldson. FFA16-0105. Says to use 20w oil above 50 degrees.Also underneath whats left of the label,on the bottom pan you can see it was originally galvanized. Mostly surface rust now, although inside of pan looks ok. Can tell better when I clean it up.

" Donaldson Oil Washed Air Cleaner"

Utahclaimjumper · October 17, 2019, 08:28:45 AM

When cleaning this type air cleaner ,,pay particular attention to the inside of the bottom pan.. Look for rust holes thru the bottom.. Water is heavier than oil and settles to the bottom ,, over time it will create leaks thru the bottom..>>>Dan
(When it does this it makes a hell-a-va mess)

TomC · October 17, 2019, 08:52:37 AM

Nobody but nobody uses oil bath air cleaners anymore. Just look at the front of a giant mining dump truck and you'll see several dry air cleaners in a row. The best way you can service your oil bath air cleaners is to replace them with a dry air cleaner. None of this servicing stuff, just replace the paper element every so often when needed. But-yoouz chooze yoouz wayz of doin stuff. Good Luck, TomC

richard5933 · October 17, 2019, 09:07:02 AM

Quote from: TomC on October 17, 2019, 08:52:37 AM
Nobody but nobody uses oil bath air cleaners anymore. Just look at the front of a giant mining dump truck and you'll see several dry air cleaners in a row. The best way you can service your oil bath air cleaners is to replace them with a dry air cleaner. None of this servicing stuff, just replace the paper element every so often when needed. But-yoouz chooze yoouz wayz of doin stuff. Good Luck, TomC

Have you seen anyone re-use these large single oil bath air cleaner housings to install a paper element? Obviously modification inside the canister would be necessary, but by re-using the outer canister the connections to the bus and the OEM look would be maintained. I know that a paper version was available from the factory, but I haven't seen one in person yet.

chessie4905 · October 17, 2019, 12:59:58 PM

Ill keep using that oil bath. Pretty impressive design. Gallon of oil instead of 80 to 150 dollars for a paper one. Labor intensive designs are a thing of the past. There is more profit in selling paper elements. I might go to paper if I ever turbo the engine, but mine is fine for that engine.