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Topic: Generator: Oil blow-by in the air filter housing (Read 1108 times) previous topic - next topic
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Generator: Oil blow-by in the air filter housing
We have a 2011 Mid Bath with the standard issue Onan Microquiet 4000 generator. The genset has just over 100 hours of run time. 

For some time now we have been seeing small amounts of oil blow-by (corrected from "blowback") in the air filter housing.  The blow-by has also contaminated the larger area adjacent to the filter housing (by aerosol?).  See the photo.

Any ideas as to what could be causing the problem?  Does the problem need immediate attention?
Jim & Sue
Formerly owned: 2011 27' MB, Sidra
Re: Generator: Oil blowback in the air filter housing
Reply #1 –
Check the oil level, sounds like it might be overfilled.
Jota
96 23.5 FL
Re: Generator: Oil blowback in the air filter housing
Reply #3 –
The PVC leaf valve is known to cause this problem.
https://duckduckgo.com/?q=r+Onan+4000+Microquiet+PCV+Leaf+Valve&t=osx&iax=videos&ia=videos&iai=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DRupB6qjCF6w

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Generator: Oil blowback in the air filter housing
Reply #4 –
Many Youtube videos recommend actually keeping the oil level right at the bottom of the oil level on the dipstick hashmarks. I believe the genset called for 1.6 or 1.7 quarts and you should fill it with closer to just under that.
Joe B.
2008 26ft  grey/white Rear Bath
NE88 caravan club
Re: Generator: Oil blow-by in the air filter housing
Reply #5 –
Thanks to all for the suggestions.

We removed 6 .oz oil, which brought the dip stick fill indication to just a hair above the Add mark (lower notch).  We will regularly monitor the air filter housing for blow-by during the next two or three hours of run time.  We hope this solves the problem, but...

(Herein the reader becomes absolutely clear that Sue and I know nothing about engine design and mechanics.)

As we learned on the way down the rabbit hole opened by the video Larry linked to, some amount of blow-by is expected. Blow-by is comprised of combustion gases that have leaked past the piston rings into the crankcase. The video is about replacing the “leaf valve” (called the breather valve in the Onan Parts Manual and the reed valve in the Service Manual). It lives behind the valve cover in the crankcase. The breather valve vents the blow-by back to the air intake manifold. This wikipedia article was our introduction to crankcase ventilation systems (CVS) and the positive crankcase ventilation (PCV) system: Crankcase ventilation system - Wikipedia.  We also consumed many other sources of information.

Now armed with enough information to be dangerous, if after a couple hours of run time the amount of blow-by is still excessive (leaks out of the air filter housing or accumulates in puddles at the bottom of the housing), we will remove the valve cover and inspect the breather valve. We will have a replacement valve cover gasket in hand. Which leads me to, who is the best source of Onan KY parts?  The Onan Cummins online parts store doesn’t impress (shop.cummins.com).

The Crankcase Ventilation System description in the screen capture is from the Onan KY Service Manual.

Jim
Jim & Sue
Formerly owned: 2011 27' MB, Sidra
Re: Generator: Oil blow-by in the air filter housing
Reply #6 –
"We hope this solves the problem, but..."

By cranky, I believe you've learned a bit! I didn't know any of that and am glad for it.

Hope the next generation picks up on the info.   LazyBones2, are you listening??
Steve S.
Lazy Bones & Cedar
2004 30'IB (Island Bed)
Yesterday is History, Tomorrow is a Mystery
Live for the day!
Re: Generator: Oil blow-by in the air filter housing
Reply #7 –
I recently did an oil change on my Emerald Plus.
Got the Onan part number for the filter from a Cummins shop, who did not have one in stock.
Took that part number to a good NAPA store who was able to cross reference it to one
they had.
You might try obtaining the part number of the things you need and check with NAPA.
Jota
96 23.5 FL
Re: Generator: Oil blow-by in the air filter housing
Reply #8 –
Quote from: Jota  - 
I recently did an oil change on my Emerald Plus.
Got the Onan part number for the filter from a Cummins shop, who did not have one in stock.
Took that part number to a good NAPA store who was able to cross reference it to one
they had.
You might try obtaining the part number of the things you need and check with NAPA.

Forget Napa,

Save some money and buy your Onan parts off of Amazon. A much easier return process, you'll get an actual OEM Cummins part, and it'll be cheaper. I've bought air filters, an OEM carburetor and Cummins motor oil directly from Amazon for my 4000. I also have bought many Dometic and even my replacement Progressive Dynamics converter directly from Amazon.
Joe B.
2008 26ft  grey/white Rear Bath
NE88 caravan club
Re: Generator: Oil blow-by in the air filter housing
Reply #10 –
Quote from: brewersarcade  - 
Forget Napa,

Save some money and buy your Onan parts off of Amazon. A much easier return process, you'll get an actual OEM Cummins part, and it'll be cheaper. I've bought air filters, an OEM carburetor and Cummins motor oil directly from Amazon for my 4000. I also have bought many Dometic and even my replacement Progressive Dynamics converter directly from Amazon.

I'd rather give my business to the local NAPA than Amazon.
I'm currently camped out about 100 miles away from a place that I could get Amazon delivered.
And my buddy got some fuel filters from Amazon that were being advertised as Onan original.
Only to get some aftermarket ones instead.
The local NAPA has no problem with returns which is much easier than having to deal with Amazon with no waiting.
Jota
96 23.5 FL
Re: Generator: Oil blow-by in the air filter housing
Reply #11 –
Quote from: Jota  - 
I'd rather give my business to the local NAPA than Amazon.

And my buddy got some fuel filters from Amazon that were being advertised as Onan original.
Only to get some aftermarket ones instead.

This is a common problem with Amazon, you have to be very careful not to get a cheap, no-name part instead of the real, brand-name part. So many products from Amazon are from unrecognizable companies, making it near impossible to pick quality parts.

Napa has saved us more than once while traveling but be sure to pick 'pro-grade' parts instead of the 'value' line.

A worn or damaged engine can produce excessive blow-by with exhaust gases escaping past the rings into the crankcase.

Larry


Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Generator: Oil blow-by in the air filter housing
Reply #12 –
My 2003 Lazy Daze has had this problem for years. We have generally not used the Onan genset for camping and almost all of the hours on it are from giving it exercise. In November of 2020, a massive wind storm took out our power for 3 1/2 days. The Onan allowed us to keep our house refrigerator and freezer in service but every time I used the genset, oil would drip from the air cleaner and I would have to add oil before each use.

Thanks to the video Larry posted, I am going to try replacing the reed valve. Looking at numerous online sources for the valve and gasket was futile. It appeared "out of stock" everywhere.

Today I visited a Cummins Service Center; while they did not have it in stock, they were happy to order both items for me and assured me they would be available by Wednesday, 9/21. I found their pricing to be quite reasonable too. The valve was $8.67 and the gasket is $5.96. I have always found their parts pricing to be better than buying oil and filters at Camping World.

I will report back when I have the parts. Not sure when I will install the valve but it looks pretty straightforward.

Steve K
Steve K

2003 Mid-bath
Re: Generator: Oil blow-by in the air filter housing
Reply #13 –
Just a follow up to the parts order I placed through Cummins Service Center. The reed valve and gasket were ordered and delivered as promised. Good service is certainly appreciated these days.

I don't plan installation for a few weeks; then I hope to report the oil dripping out of the air cleaner issue will be history.

Steve K
Steve K

2003 Mid-bath
Re: Generator: Oil blow-by in the air filter housing
Reply #14 –
Hi Group, I wanted to make a follow up report on the oil blow by issue I was experiencing with my Onan Microquiet generator.

Our LD is a 2003; we have had had a persistent problem with oil dripping below the generator compartment after running the generator for years. I had oil dripping out of the air filter housing when the generator was running and then a mess in the compartment. I used to think it was the oil drain plug dripping.  Thanks to Larry Wade's reference the the breather valve and the link to the video, I ordered parts from my local Cummins Service Center. Some how I ordered the wrong valve cover gasket (my fault, I should have taken my Onan model number and serial number with me)

Correct part # for the breather valve for my generator was #123-1920. Cost was less than $9.00
Correct valve cover gasket for my generator was  #110-3861. Cost $9.02

The job was easy;  simply remove 7 bolts attaching the valve cover. My valve cover came off with the gasket still intact so never used the new gasket. I discovered that the breather valve had been installed inside-out when the generator was manufactured causing a dent in the original metal valve. The person in the You Tube video seemed concerned about valve orientation as he made his video. Now I know why. I referenced the diagram from Onan's manual to confirm proper orientation of the valve.

After installing the new breather valve, I can report I no longer have oil dripping from the air filter. 😀

Steve K.
Steve K

2003 Mid-bath
Re: Generator: Oil blow-by in the air filter housing
Reply #15 –
Glad to hear that your oil leak is solved. I’ll bet that made your day, or year!
Warren
2019 MB “Dream Catcher”
Jeep Wrangler JL
Re: Generator: Oil blow-by in the air filter housing
Reply #16 –
Thanks Warren!

Winning the Powerball Lotto would have made my year! Fixing the Onan oil leak left me with a satisfying feeling since it was another item off of my project list.

Wednesday we parked the Lazy Daze for winter and put the cover on it. Last evening as I sat back with an adult beverage, I started on my 2023 "Things to do next spring" list. Then I realized that June 2023 will be our 20th anniversary of ownership. Time flies when you're having fun!

Steve K.

Steve K

2003 Mid-bath
Re: Generator: Oil blow-by in the air filter housing
Reply #17 –
Quote from: Steve K.  - 
Wednesday we parked the Lazy Daze for winter and put the cover on it. Last evening as I sat back with an adult beverage, I started on my 2023 "Things to do next spring" list. Then I realized that June 2023 will be our 20th anniversary of ownership. Time flies when you're having fun!

Time does fly, our LD's 20th birthday is next month, in mid-December
We need to have a party for the twenty-year-old LDs, 2003 had a bumper crop of them.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Generator: Oil blow-by in the air filter housing
Reply #18 –
Hi Steve K. Had you still been using the Nucamper signature line I would have recognized you before now.  On February 14, '23 our 'BlueBelle' will be 23 years young!  I got the call a few days earlier, but was working a 'production' schedule, so my first day off was Valentines day.  I didn't find out about the Lazy Daze online presence until 2002. Too bad the factory didn't tell me about the  'Lifewithalazydazerv' at Yahoo then.  They probably didn't have 'internet' back then!        RonB 
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Generator: Oil blow-by in the air filter housing
Reply #19 –
Hi Ron! If you look at my profile, my user name is still nukamper2000. I used that name because my wife and I started  our camping trips in 2000 with a travel trailer. I think when this group transitioned from Life With a Lazy Daze Rv, my nukamper2000 name sort of disappeared.

Larry is so correct about the Class of 2003 Lazy Dazers. We discovered the Lazy Daze brand in 2002 and ordered our Midbath in October 2002. We were so eager reading the delivery reports from that era. Larry W, Ted H (wxtoad), Joan (known as JC) and Lorna D. are some of the names that I recall as being new owners and we got to live vicariously through their reports. There was a very active database of orders that allowed you to gage when you could expect to "Get the Call!" from Vickie at the Mothership. That database included your order date and number, floorplan, and then the actual date of delivery. That was when the factory was humming along making around 200 units per year. I think they had two deliveries scheduled each day of the week, Monday-Friday.

Ron, your unit was a Valentine gift that has no doubt become a member of your family. 23 years! Wow!

It would be interesting to learn of the repairs made to our Ford chassis. I am sure there must be some great stories about some of our rigs!

Nukamper2000, aka Steve K
Steve K

2003 Mid-bath
Re: Generator: Oil blow-by in the air filter housing
Reply #20 –
As the OP of this topic, I owe you all a follow up.

When last I reported (Sept., 2022), we had removed 6 oz of oil from the oil pan in the hope that that would solve the problem.  Well, it didn’t.  So, we bought a new breather valve and valve cover gasket and set about reproducing Steve K’s results.  Thank you, Steve, for leading the way.  The replacement process went just fine.  Unlike Steve’s experience, we had to replace the valve cover gasket.  Post replacement, after a one hour run (50 minutes under load), we found no oil in the air filter housing.  Success.  Time will tell if it’s to be a lasting success. 

The following are some details of my replacement experience.  

I sourced the breather valve and valve cover gasket directly from Cummins, which required calling their customer service department (800-286-6467).  For some reason, the valve cover gasket is not in the online catalog.  The service rep didn’t seem to have any trouble finding it.

Before removing the bolts from the valve cover, I used a torque wrench to determine the existing torque on the bolts.  The torque varied from 8 nm (5.9 ft-lb) to 10 nm (7.5 ft-lb).  Upon reassembly, they were torqued to 10 nm.  The day after the test run, I checked them again; all needed additional tightening to get back to 10 nm.

With the valve cover off it became apparent that
   1.  the gasket holds the breather valve in place (see photos), therefore, the gasket had to be removed to replace the breather valve.
   2.  there was a good bit of oil in the chamber with the breather valve.*
   3.  the breather valve was installed correctly, but does not look exactly like the illustration in the Service Manual.**

*The “good bit of oil” in the chamber behind the breather valve was about 2 Tbs. In front of it, in the upper chamber of the valve cover, was maybe another 2 Tbs, much of which, when the cover was removed, spilled down onto the valve springs and rocker arms. (Not a problem.)

**Where the upturned piece of metal and two rivets are shown on the left of the valve in the illustration, they are, in reality, on the right.  See the photos.  Also, notably, the guy in the video that Larry linked to installed the valve in the only other possible orientation, which has the rectangular metal box (on the back of the valve in the diagram) facing out.  Both Steve and I rejected that option.

The new breather valve differed in a tiny way from the original valve.  The difference is in the placement of a tiny hole.  In the original valve the tiny hole is under the riveted pieces; in the new valve the hole is above.  See photos. 

Removing the valve cover gasket and preparing the surface for the new gasket was the most time-consuming part of the process. 

Here are some questions for an Onan MQ 4000 tech wizard:
   With a perfect condition MQ 4000 generator, how much blow-by is normal?
   How often is a defective breather valve to blame for excessive blow-by?
   What is the purpose of the tiny hole in the breather valve?  What would happen if it was missing or blocked?
   Is all that oil behind the breather valve and in the upper chamber of the valve cover normal?
Jim & Sue
Formerly owned: 2011 27' MB, Sidra
Re: Generator: Oil blow-by in the air filter housing
Reply #21 –
Hi Jim & Sue,

Thanks for posting your excellent follow up report. Good to learn your project appears successful. I owe you a thank you for posting about your problem and Larry for linking to the video.

After several times exercising the genset, I have not seen any oil dripping from the aircleaner housing. I guess I was lucky that the gasket remained intact on the valve cover when I removed the valve cover. I never noticed the hole in the reed valve; I was paying more attention to the orientation of the reed valve since it seems Onan had installed my unit's valve incorrectly. No wonder mine leaked from day 1.

Hope you get your Onan questions answered too.

Steve K
Steve K

2003 Mid-bath