Hi All, long post but hopefully it will help some.
So after acquiring a used Monaco with a Cummins 425 ISL, that clearly was not mechanically maintained as it should be... I started having a crankcase pressure error on my coach. This seemed to be occurring mostly when towing a toad, and/or using the engine brake, especially when heavy acceleration was happening going up a grade.
Based on the forums I decided to take it to Cummins in Las Vegas, big big mistake. To sum it up in a nutshell, they don't build those big Cummins service shops from little repairs, kind of like the casinos in Vegas aren't built because there are so many winners... In short, they wanted to charge me over $10k for a new head, and that was just to start, as they were expecting to find other issues... Mind you, my bus had only 30k miles on it, runs like a top, doesn't burn oil or have any smoke at the tail pipe, doesn't run hot or have water in the oil, etc. Told them no thanks don't crack my engine open. This along with other communication issues and a generally crappy experience was beyond disheartening, and clearly their troubleshooting was sub-par.
So being fairly mechanically inclined, I started looking at the issue. Now I had previously replaced the crankcase filter (and sensor), but I decided to take a look at it again, it was soaked with oil. I replaced it again with a new Cummins one, blew out the oil drain lines and the draft tube on the oil separator. Plus, I discovered that the oil separator had a split O-ring that was clearly causing some of the issue, as well as the crankcase was overfilled with oil, contrary to what the dipstick said... So, after those fixes and a few test rides watching the crankcase pressure on my Bluefire gauges, it was considerably better and no codes. Keep in mind converting the hydrometer pressures to psi were talking about .5 psi (ish) tripping the error code on your dashboard. I didn't have any teakettle issues with the oil fill cap, but I could feel a little air coming out the top, so I decided to do the following mod with a vented catch can (see attached pic) and a modified fill cap with a brass hose barb. I didn't even need a vacuum source or pump, it just needed to breath. It works great, and no significant fluctuations on the crankcase pressure gauge at all!
Fix-it-bob (aircraft mechanic) on this site came up with a fix for his 425 ISL (that I didn't try as this worked for me), but basically he made his own maintenance free crankcase filter, like the ones offered for the ISC, but none are offered for the ISL... This in light of the fact that Cummins knows there is an issue with the ISL pressure (see attached warranty recall, but only for firetrucks?...) Bob removed the paper/fiber element from his filter, and also removed the check valve, and he has reportedly had no issues in the last year!
We are hoping that this info on fix options will help those who are having similar minor issues with crankcase pressure error codes. Also to not be taken advantage of by Cummins, and to find a fix they are not offering instead of paying big bucks. Or dumping your rig on some poor sap, like happened to me. Not saying this will help everyone but try some other options before letting them stick it to you on what could be a simple fix. Clearly if your head gasket is blown, etc and there are supporting symptoms of such, then it is what it is.
Safe travels and hope this can help others, as I too was frustrated by the number of folks dumping rigs out of fear and found for me what is a simple fix. One that only ended up costing me a couple hundred bucks...
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Looks great!
I'm digging the vent tank, I use a Cummins Fleetguard crankcase ventilation system on mine, but my vintage engine doesn't have a crankcase filter.
Shame that Cummins didn't pick up the fact the engine was overfull oil. Many motorcoaches have mis-marked dipsticks. Next service, fill it with the amount of oil listed in Quickserve and then see where "full" really is.
Keep in mind however, now that you've "opened" up the crankcase ventilation system, you'll not get a high crankcase pressure DTC when the filter gets restricted, be best to put it on a regular replacement schedule, like 50k miles or something.
EDIT: I see you left the crankcase filter out.
Pic is my Fleetguard crankcase ventilation system oil separator. Mine has a drain hose that lets any oil drain back to oil pan.
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1999 American Eagle
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How did the crankcase get overfilled? Seems that could cause a pressure warning.
I have exactly the same year, make, & model. My engine light is mounted horizontally. These things are unicorns.
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2009 Monaco Camelot 42PDQ
2011 JK
How did the crankcase get overfilled? Seems that could cause a pressure warning.
I have exactly the same year, make, & model. My engine light is mounted horizontally. These things are unicorns.
It was filled to full on the dipstick, which is over what the manual calls for in quarts (after measuring). I just keep it in the middle now and that seemed to have cured the problem. I added the breather after the fact for extra reduction in pressure.
I’m just curious if you inspected the engine for dust ingestion? 14” H2O of blowby would be quite concerning to me
Cummins did not. As I mentioned no outward signs of any issues, no oil consumption, starts easy and no smoke out the pipe when starting or while running. Power is good too. It only had 27k miles on it when I bought it. When I changed the air filter (I changed every filter to be safe) it seemed to be intact with no obvious internal damage. The boot and intake pipe were internally clean and had been clamped tightly. Now I have not had a chance to look at the turbo intake, but when I do I will update this post.
Hello jmfixitman
I had the EXACT same problem as your did with my ISL 425HP. Took it to Cummins in Albuquerque. They wanted $20K for in frame repair.
I went back home to Illinois later and took it to a very reputable diesel truck shop which works on motorhome also. Showed him the oil analysis I had done. Same questions you were posed - starting, running, no smoke. Changed the cranckcase filter was his recommendation. He stated "Was the coach sitting for awhile, and when was the crankcase filter was changed?" He stated that he has seen many times when the filter was not changed, the pressure builds up and the alarm is set off.
I changed the filter and the problem went away. I call this the $20K filter.
I agree with you - Cummins repair shops are thieves and robbers. Motorhome owners you have been informed and made aware now.
!
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