Author Topic: Air dryer purge cycle spewing engine oil  (Read 2928 times)

Chuck Jackson

  • BAC Member
  • *
  • Posts: 171
  • Thanked: 53 times
Air dryer purge cycle spewing engine oil
« on: August 10, 2018, 11:35:23 PM »
We’ve had issues from day one (dec 2013) where the purge cycle has spewed some oil. I thought this was normal but even after replacing the compressor, it is still spewing oil during the purge cycle...enough that after about 800 miles, my catch can had about 2 oz of oil. It seams to have gotten worse. One of my ping tanks even had some oil in it when I went to drain it. It never had anything in it in the past. I am thinking about changing the desiccant filter even though it has been changed twice in 5 years and about 15k miles so I can finish the Rally and have it looked at when I get home. Am I doing any damage with this thought?
2019 Newmar Dutch Star 4328
2008 Beaver Contessa 40' Pacifica 425 Cat - Sold

Mike Shumack

  • Guest
Re: Air dryer purge cycle spewing engine oil
« Reply #1 on: August 11, 2018, 01:15:11 AM »
You should change the air dryer filter since it will plug up and pass oil into the rest of the air system (oil in the system can cause the rubber seals in the brake valves to swell and lead to brake valve leakage/failure).
There is a good video series on the CAT engines by "Adept Ape" - here is the one on air compressors https://www.youtube.com/watch?v=846bVMd_J4Q

He mentions that there is an updated air compressor (if you don't already have the updated compressor - just be aware of it in case you need a new compressor). The old style is a twin-piston (which he says is more prone to failure), the new style is a Bendix single-piston compressor.

The three common causes of oil in the air system is 1) compressor rings worn/leaking, and 2) restriction in the air inlet (clogged air filter and/or restriction in air inlet hose to compressor), and 3) excessive compressor cycling (leaking air system, faulty governor, etc.).

The easiest/best thing to do now, is change the air dryer cartridge and check the air inlet hose and filter for restriction.

Dave Atherton

  • BAC Member
  • *
  • Posts: 1015
  • Thanked: 877 times
Re: Air dryer purge cycle spewing engine oil
« Reply #2 on: August 11, 2018, 01:41:46 AM »
Chuck,
This is normal although it looks worse than what is happening. The air system removes the moisture in the compressed air within the air system. A certain amount of engine oil from air compressor compresses with moisture and exhausts at the pop off valve on the bottom of air dryer. There is no problem as far as damage to your system and again this is normal. One can tell if the air dryer replacement cartridge needs replacement when the pop off valve starts popping every 30 seconds or so. As replacement cartage gets to end of life the valve will pop off every 20 seconds and you will notice during the fast pop off cycles the purge valve will not completely shut off on the air dryer. Then, at some point, you will stop for lunch and cannot build any air pressure after restarting the engine. The reason the engine oil looks worse, is that your air system ( air dryer ) needs to be serviced. I left out details about the air system wet tank and dry tank because you are already exhausting engine / moisture at pop off valve on bottom of air dryer.
Ask Dave, Dave Atherton Retired Cat Mechanic
« Last Edit: August 11, 2018, 02:12:34 AM by Steve Huber Co-Admin »

Steve Huber Co-Admin

  • Administrator Group
  • *
  • Posts: 3503
  • Thanked: 2689 times
Re: Air dryer purge cycle spewing engine oil
« Reply #3 on: August 11, 2018, 02:15:02 AM »
Mike,
Thanks for the utube video link. I've added it to the Video Links post in the Private BAC board. http://beaveramb.org/forum/index.php/topic,5632.msg42093.html#msg42093
Steve
Steve
2015-          07 Contessa Bayshore C9,  400 hp
2013-2015: 00 Marquis Tourmaline, C12, 425 hp
2005-2013: 01 Contessa Naples, 3126B, 330 hp

Chuck Jackson

  • BAC Member
  • *
  • Posts: 171
  • Thanked: 53 times
Re: Air dryer purge cycle spewing engine oil
« Reply #4 on: August 11, 2018, 03:18:04 PM »
 Thanks Mike and Dave. I think I’m going to error on the side of caution and replace the filter. If nothing else it will help keep oil from spattering all over my engine compartment at least for a short period.  I will definitely have this looked at ASAP when I get home.

BTW - Mike,  i’ve watched his videos in the past and they’ve been quite helpful in helping me learn about my engine!
« Last Edit: August 11, 2018, 03:23:27 PM by Chuck Jackson »
2019 Newmar Dutch Star 4328
2008 Beaver Contessa 40' Pacifica 425 Cat - Sold

Dan Murphy

  • Guest
Re: Air dryer purge cycle spewing engine oil
« Reply #5 on: August 11, 2018, 04:30:22 PM »
Yep! Change the filter. I have made it a regular maintenance item and change it much sooner than the manual suggests.

Dave Atherton

  • BAC Member
  • *
  • Posts: 1015
  • Thanked: 877 times
Re: Air dryer purge cycle spewing engine oil
« Reply #6 on: August 11, 2018, 05:12:01 PM »
Gentleman, the reason we are talking oil/ moisture exit from air dryer on purge cycle because
The air system is backed up with moisture. This is from lack of service that nobody talks about
and being we are not mechanics do not understand. First starting at the air compressor basic
trouble free operation, compressed air than goes to what is called a wet air tank and has a check
valve that will open at 90 psi and allow air to go into what is called a dry tank. From this dry tank
discharge air than goes to the air dryer where any moisture is retained in a replacement filter
and air dryer will cycle. The air dryer works trouble free when maintain at regulator service,
The down side to not maintain air dryer your air system gets backed up with moisture/mix oil
through out air system. If this happens replacements of filter will fill up real fast and will need to
cycle several filters to clean up the system. A person can and several have put on auto-drain
Valves on ther wet tank and dry tank ( easy task just remove plug on bottom on air tank install
valve )  now moisture does not get into air systems. Ask Dave, Dave Atherton Retired Cat mechanic

Mike Shumack

  • Guest
Re: Air dryer purge cycle spewing engine oil
« Reply #7 on: August 11, 2018, 05:48:20 PM »
My setup is different from what you describe.
Air from Compressor goes to Dryer first then to Wet tank. So if the Air Dryer is doing its job no moisture (or oil) gets to the Wet tank.

More like in this diagram:

Dave Atherton

  • BAC Member
  • *
  • Posts: 1015
  • Thanked: 877 times
Re: Air dryer purge cycle spewing engine oil
« Reply #8 on: August 11, 2018, 09:35:02 PM »
Mike, answer to your question is yes when air dryer is maintained, other wise moisture will
go through system and will not clean up with one filter. Note: these filters absorb moisture
In the system and when filter cannot absorb the cycle time on purge valve will be faster and
faster. This as my first post the purge valve will stick open and you cannot build air. There
are several different ways to install air dryer into the air system, but the results are the same.
Ask Dave, Dave Atherton Retired Cat Mechanic
The following users thanked this post: Joel Ashley

Joel Ashley

  • BAC Member
  • *
  • Posts: 2341
  • Thanked: 801 times
  • OSU Class of '73, Oregon Native. RVing 39 years
Re: Air dryer purge cycle spewing engine oil
« Reply #9 on: August 11, 2018, 10:56:08 PM »
Our’s is set up similar to what Mike describes, so the air is dried prior to entering the tanks.  But as Dave notes as long as it’s dried before entering the device lines...

Joel
Joel and Lee Rae Ashley
Clackamas, Oregon
36.9 ft. 2006 Monterey Ventura IV, aka"Monty Rae"
C9 400HP Cat