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Onan oil leak [message #368861]

Sun, 20 February 2022 11:39

Scott Nutter

Messages: 782
Registered: January 2015
Location: Houston/San Diego

Karma: 4

Senior Member

Hello,
My onan will blow oil through the lower screen while running. Not a huge amount, but just enough to dirty up the area. From reading past threads, it seems the main culprit could be the oil filter adapter is leaking and the cooling fan sucks out the oil via the screen. The only experience I have with the onan is changing the oil and filter.
What is the best method to access the oil filter adapter? Or is there something else I’m overlooking?
Thanks, Scott.

Scott Nutter 1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final drive, Quad bags, Dave Lenzi super duty mid axle disc brakes, tankless water heater, everything Lenzi. Alex Ferrera installed MSD Atomic EFI Houston, Texas

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Re: Onan oil leak [message #368862 is a reply to message #368861]

Sun, 20 February 2022 12:49

lqqkatjon

Messages: 2324
Registered: October 2010
Location: St. Cloud, MN

Karma: 5

Senior Member

Usually only 3 places the onan leaks. All are fairly easy to fix.

1. Oil pressure sender on side of onan. Very easy to change out.

2. Like you mentioned, the oil filter adaptor. There are 2! Gaskets. Venders should have them. Just start taking off the cover on back side
Of generator and it is fairly self explanatory.

3. Main oil seal behind the flywheel. Take off the front cover and flywheel. (Need s timing gear puller). And carefully extract and replace that is also a fairly easy job.

Any of those and even a small leak makes a big mess.

Jon Roche 75 palm beach EBL EFI, manny headers, Micro Level, rebuilt most of coach now. St. Cloud, MN http://lqqkatjon.blogspot.com/

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Re: Onan oil leak [message #368863 is a reply to message #368861]

Sun, 20 February 2022 12:51

Tilerpep

Messages: 404
Registered: June 2013
Location: Raleigh, NC

Karma: 7

Senior Member

A distributor wrench makes the oil pressure sender much easier to change. like:

https://www.northerntool.com/shop/tools/product_200806236_200806236?cm_mmc=Google-LIA&utm_source=Google_LIA&utm_medium=Hand%20Tools%20%3E%20Wr enches%20%3E%20Specialty%20Wrenches&utm_campaign=Wilmar&utm_content=9094070&gclid=CjwKCAiA6seQBhAfEiwAvPqu1xs10O2b8ILL49s4PciPtRGN3sGt88tM PYcS0g2CqyFYRufBb_ff9xoC0nMQAvD_BwE&gclsrc=aw.ds

1975 Glenbrook, 1978 Royale rear bath Raleigh, NC

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Re: Onan oil leak [message #368864 is a reply to message #368861]

Sun, 20 February 2022 15:37

Scott Nutter

Messages: 782
Registered: January 2015
Location: Houston/San Diego

Karma: 4

Senior Member

Jon, will all 3 of those locations blow oil out the screen on the bottom?
Thanks, Scott

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Re: Onan oil leak [message #368865 is a reply to message #368864]

Sun, 20 February 2022 16:47

Jim Miller

Messages: 501
Registered: March 2008

Karma: 10

Senior Member

Scott Nutter wrote on Sun, 20 February 2022 16:37

Jon, will all 3 of those locations blow oil out the screen on the bottom?

Yes absolutely. Our Onan is a pull-through cooling system meaning that air is pulled into the generator section, then over all cooling surfaces of the engine and then into the center of the flywheel from which it is "flung" outward into the blower housing and out the discharge in the bottom. Any oil leaks from crankshaft seals or the oil filter mount area will be pulled through and discharged as well.

--Jim

Jim Miller 1977 Eleganza II 1977 Royale Hamilton, OH

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Re: Onan oil leak [message #368866 is a reply to message #368861]

Sun, 20 February 2022 16:54

Tilerpep

Messages: 404
Registered: June 2013
Location: Raleigh, NC

Karma: 7

Senior Member

My sender was bad early in my knowledge curve…it was pouring oil out and I thought main front seal was bad. Huge mess. Sender was cheap and easy with the wrench I linked. That was all that was wrong (that time)

1975 Glenbrook, 1978 Royale rear bath Raleigh, NC

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Re: Onan oil leak [message #368867 is a reply to message #368866]

Sun, 20 February 2022 17:04

Jim Miller

Messages: 501
Registered: March 2008

Karma: 10

Senior Member

Tilerpep wrote on Sun, 20 February 2022 17:54

My sender was bad early in my knowledge curve…it was pouring oil out and I thought main front seal was bad.

I would advise going after low hanging fruit first - the oil sender. Only after replacing the sender should one go after the two gaskets on the oil filter mounting bracket... why? Replacing those gaskets requires a little surgery because the right front engine hanger goes all the way from the cushion on the top right slide mount down beside the block and then over the two oil filter bracket mounting bolts; the engine in essence "hangs" from those two bolts. You have to take a bit of stuff loose and support the engine from below in order to get that hanger out.

Only after trying both of those things would I go after the front crank seal. Spoken from experience. Smile

--Jim

Jim Miller 1977 Eleganza II 1977 Royale Hamilton, OH

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Re: Onan oil leak [message #368868 is a reply to message #368861]

Sun, 20 February 2022 18:46

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

Scott,

I must admit that I was part of this rodeo more than a few times and even my own once. Mine is a BF and not an NH, but that does not seem to matter.

First, read what Jim Miller wrote and take it to heart.

Next, plan to make a day of it (when it is nice and warm and dry). Get a couple of cans of brake cleaner and some spray deodorant or foot powder.

With the package all the way out the rails, a 7/16 socket and can, undress the unit. That means take off everything that you can unscrew.
Now clean it as best you can. Then spray the powder on all the places it might leak.
Now read carefully - Position yourself clear of the flywheel. Run the unit for 30~45 seconds and shut it down. It you can't see the leak, run it again, but never even near a minute. Running like this, the engine has no cooling at all and it can easily be damaged.

Wash the fins of the flywheel and powder them too. Put back on the cylinder head covers and run it a little longer. It will have cooling now, but it is still dangerous.

There is one more very common leak that I have hit several times.
Take all the covers off and look at the flywheel fins... Are there oil tracks there?
Still can't find it?? One more place to look that is not easy, but as said, I have seen this a couple of times now. Look between the flywheel and the engine. What is back there is the timing gear cover. You might be able to see it from both sides. Try to clean it as best you can. If you can powder there, that would be good. Do another short run. If it is the timing cover, oil usually runs straight down the join when the covers are off.

Several times now, I have taken a flywheel off to find all the fasteners of the timing cover loose. The first time I found this, I was not of a mood at that time to go into the engine that far, so I just snugged up all the screws and put it back together and made a mental note to deal with it some other time. That was my Onan and this was about 15 years ago and it still leaks a little, but not enough to matter and I will get at it some day (year).

Matt

Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

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Re: Onan oil leak [message #368869 is a reply to message #368861]

Sun, 20 February 2022 20:53

Scott Nutter

Messages: 782
Registered: January 2015
Location: Houston/San Diego

Karma: 4

Senior Member

Thanks Matt. I will print out your reply and spend some time on it. I have a Honda EV6010 I rebuilt a few years back to replace the onan with. But the onan still runs great. Right now I would rather repair than replace. And thanks to all, Scott

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Re: Onan oil leak [message #368870 is a reply to message #368861]

Sun, 20 February 2022 20:57

Scott Nutter

Messages: 782
Registered: January 2015
Location: Houston/San Diego

Karma: 4

Senior Member

And Jim, thank you as well. I’m following your advise. Scott.

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