Change Your Crankcase Air Filter

[Tyro2004]

I finally found my Crankcase Air Filter and it was absolutely bad! Its safe to say it has never been changed by the previous owner.

I was changing my air filter out and just below where the air filter goes is the crankcase filter in the air box. I’m sure it’s only on the big blocks but if you have an older MH like me, Check to see if you have one. I Changed it with Motorcraft - FA1603

Here are some pictures:

Motorhome:
1995 Winnebago Vectra Series M-33RQ
FORD F53 V8 460 7.5L EFI

[Ray,IN]

All newer Cummins engines size L9 and up have a crankcase breather filter, either open or closed system. One company even makes an add-on for old engines like mine. A dirty one can cause high pressure internally.
I suspect like you found, most do not know about it or neglect to replace during scheduled maintenance.

[Tyro2004]

Originally Posted by Ray,IN

All newer Cummins engines size L9 and up have a crankcase breather filter, either open or closed system. One company even makes an add-on for old engines like mine. A dirty one can cause high pressure internally.
I suspect like you found, most do not know about it or neglect to replace during scheduled maintenance.

Nice! Thanks for the information. I kind of wondered what the filter actually does for the interior of the engine. I almost thought it was to help PCV and so it stops back pressure?

Yes, your right about people not even knowing about it. I hope the thread helps to remind others.

What diesel pusher do you have?

[NCC-1701A]

Originally Posted by Ray,IN

All newer Cummins engines size L9 and up have a crankcase breather filter...

My motorhome has an ISL9 built in 2012. The owners manual states to change at 60,000 miles or 2000 hours. No requirement for any specific calendar time period...just usage based.

The book also covers the ISC and the change interval was the same.

Not sure if this has changed for other years, but just relating so others know it is in the manual and to probably not be concerned if they are under this usage level since there is not a time period to be concerned with...at least per my manual.

[Tyro2004]

Originally Posted by NCC-1701A

My motorhome has an ISL9 built in 2012. The owners manual states to change at 60,000 miles or 2000 hours. No requirement for any specific calendar time period...just usage based.

The book also covers the ISC and the change interval was the same.

Not sure if this has changed for other years, but just relating so others know it is in the manual and to probably not be concerned if they are under this usage level since there is not a time period to be concerned with...at least per my manual.

Great Post man! What does the Crankcase Filter actually do? I know it’s fresh air to the crankcase but is it for the PCV valve to work correctly for burnt off moisture out of the oil? To get the pressure from oil going through the PCV system?

[NCC-1701A]

From Cummins' website:

"Cummins Filtration's crankcase ventilation systems are innovative products using patented technologies to control oil drip and crankcase emissions in diesel engine applications. The open crankcase ventilation (OCV) systems provide superior aerosol filtering of crankcase emissions, commonly known as blow-by. Blow-by is the result of high pressure gases and oils escaping around piston rings and venting to the atmosphere. This oily mist attracts dust and airborne particles, resulting in an accumulation of contaminants, both on the engine and on the surface beneath it. This condition increases the clean-up required in the engine compartment, as well as unsightly oil drips on highways, bodies of water, parking lots, crops, garage floors and driveways."

https://www.cumminsfiltration.com/eme/opencvfilters

[code2e]

Originally Posted by Tyro2004

Great Post man! What does the Crankcase Filter actually do? I know it’s fresh air to the crankcase but is it for the PCV valve to work correctly for burnt off moisture out of the oil? To get the pressure from oil going through the PCV system?

Gasoline engines have intake vacuum. The purpose of the crankcase filter is to allow clean air entry to the crankcase. The PCV valve draws combustion vapors from the crankcase and delivers them to the intake under vacuum, to be burned. There may be a slight vacuum drawn on the crankcase if the engine is in good shape.

As the piston rings wear, more blow-by is discharged in the crankcase than before. The crankcase filter will get oily once pressure is greater than vacuum because oily vapor backs up the intake. Then the filter builds up dirt faster. The filter needs more often replacement on older engines to keep from pressurizing crankcase.

[Tyro2004]

Originally Posted by code2e

Gasoline engines have intake vacuum. The purpose of the crankcase filter is to allow clean air entry to the crankcase. The PCV valve draws combustion vapors from the crankcase and delivers them to the intake under vacuum, to be burned. There may be a slight vacuum drawn on the crankcase if the engine is in good shape.

As the piston rings wear, more blow-by is discharged in the crankcase than before. The crankcase filter will get oily once pressure is greater than vacuum because oily vapor backs up the intake. Then the filter builds up dirt faster. The filter needs more often replacement on older engines to keep from pressurizing crankcase.

Wow! You and NCC-1701A explanations are fantastic. Thank you guys! I kind wonder when that technology was invented Or maybe it was always on Diesel engines. Even the old old ones mounted in factory’s with the huge balance wheel might have had them. It’s some pretty ingenious tech. If you think about it.

[code2e]

Originally Posted by Tyro2004

Wow! You and NCC-1701A explanations are fantastic. Thank you guys! I kind wonder when that technology was invented Or maybe it was always on Diesel engines. Even the old old ones mounted in factory’s with the huge balance wheel might have had them. It’s some pretty ingenious tech. If you think about it.

Both diesel and gasoline engines have always had some form of crankcase ventilation. Prior to 1967, most had an open draft tube. It was an open ended pipe aimed down at the road. Long enough to catch the wind as you were driving. This created a "draft" on the tube and helped draw the vapors out. Oil droplets as well, creating it's nickname "slobber tube". Roads were really slick after first rain in those days.