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[GMCnet] Oil sputtering (4K) Onan [message #322345] Sat, 19 August 2017 12:36 Go to next message
Olly Schmidt is currently offline  Olly Schmidt   United States
Messages: 1265
Registered: February 2014
Location: Germany and Scottsville, ...
Karma: 8
Senior Member
Morning,

my 23' is on its maiden voyage, and after some quad carb (part)rebuilt
the 455 runs much better. However the Onan doesn't like to keep its oil.

Anyone has an idea?

Quote: Oil sputtering out of the cap which doesn't appear to screw on
like the other one and the oil rebreather going into the carb
http://possy.de/onan1.jpg

After two minutes of running, there is a sizable amount of oil on the
tarmac. http://possy.de/onan2.jpg

--
Best regards

Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA

'76a Eleganza II, CA
'73 Sequoia, VA

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Best regards

Olly Schmidt
PGP Key ID: 0x18a9 3a1f 4196 bf22
'76a Eleganza II, VA
'73 Sequoia, SH, Germany
Re: [GMCnet] Oil sputtering (4K) Onan [message #322350 is a reply to message #322345] Sat, 19 August 2017 13:30 Go to previous messageGo to next message
Dennis S is currently offline  Dennis S   United States
Messages: 3046
Registered: November 2005
Karma: 2
Senior Member
Peer

Not an uncommon problem on the 4KW. The rubber plug seal on the oil dipstick gets loose and blows oil out the top.
You can try turning the dipstick handle so that the curl handle wedges against the exhaust manifolsd.
Or you can put a couple of wraps of tape around the rubber seal to help it fit more snugly.

Dennis

Peer Oliver Schmidt wrote on Sat, 19 August 2017 12:36
Morning,

my 23' is on its maiden voyage, and after some quad carb (part)rebuilt
the 455 runs much better. However the Onan doesn't like to keep its oil.

Anyone has an idea?

Quote: Oil sputtering out of the cap which doesn't appear to screw on
like the other one and the oil rebreather going into the carb
http://possy.de/onan1.jpg

After two minutes of running, there is a sizable amount of oil on the
tarmac. http://possy.de/onan2.jpg

--
Best regards

Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA

'76a Eleganza II, CA
'73 Sequoia, VA

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Dennis S
73 Painted Desert 230
Memphis TN Metro
Re: [GMCnet] Oil sputtering (4K) Onan [message #322351 is a reply to message #322350] Sat, 19 August 2017 13:34 Go to previous messageGo to next message
Dennis S is currently offline  Dennis S   United States
Messages: 3046
Registered: November 2005
Karma: 2
Senior Member
Peer

Also check this old thread for possible cures.

http://gmc.mybirdfeeder.net/GMCforum/index.php?t=msg&goto=302972&rid=904&srch=Onan+4KW+blowing+oil+out#msg_302972

Dennis

Dennis S wrote on Sat, 19 August 2017 13:30
Peer

Not an uncommon problem on the 4KW. The rubber plug seal on the oil dipstick gets loose and blows oil out the top.
You can try turning the dipstick handle so that the curl handle wedges against the exhaust manifolsd.
Or you can put a couple of wraps of tape around the rubber seal to help it fit more snugly.

Dennis

Peer Oliver Schmidt wrote on Sat, 19 August 2017 12:36
Morning,

my 23' is on its maiden voyage, and after some quad carb (part)rebuilt
the 455 runs much better. However the Onan doesn't like to keep its oil.

Anyone has an idea?

Quote: Oil sputtering out of the cap which doesn't appear to screw on
like the other one and the oil rebreather going into the carb
http://possy.de/onan1.jpg

After two minutes of running, there is a sizable amount of oil on the
tarmac. http://possy.de/onan2.jpg

--
Best regards

Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA

'76a Eleganza II, CA
'73 Sequoia, VA

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Dennis S
73 Painted Desert 230
Memphis TN Metro
Re: [GMCnet] Oil sputtering (4K) Onan [message #322376 is a reply to message #322345] Sat, 19 August 2017 20:34 Go to previous messageGo to next message
Matt Colie is currently offline  Matt Colie   United States
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
Senior Member
Peer,

As you may have read in the prior post, I was to have that exact same problem.
I can report a successful cure.

If you wrap the rubber part of the dipstick with several (I do not recall what it took) layers of teflon tape, you can make the plug hold in the tube again. The first time I tried this, I did not clean the rubber stopper off well enough and the tape slipped off. When I wrapped it up after cleaning, the tape has been on there about an hundred hours now.
Before I did that, I got an expandable rubber plug that did work in the place, but it was then a major PITA to check the lube oil level.

There is (or at least I could not locate) a replacement part. The later version use a stick that is attached to a bayonet closed cap. That is what my other BF has, but I have investigating swapping because I do not want to disable that unit.

The next problem you will have (another hundred hours or so) is that the swaging that stops the indicator from going through the plate on top of the rubber stopper will wear off and the stick goes though. This is can be a big issue, but fortunately, I had just changed the oil and KNEW it was not over full. It could have been a disaster if the lube oil level had gotten that low and I did not catch it.

I had lots of plans to repair this when I found it, but not time. So, I put a tight wrap of safety wire on the stick and will engineer a better repair during the winter layup that is all too close now.

Matt - In Paducah with GMCES and GMCGL waiting for the sky to go dark.





Peer Oliver Schmidt wrote on Sat, 19 August 2017 13:36
Morning,
my 23' is on its maiden voyage, and after some quad carb (part)rebuilt
the 455 runs much better. However the Onan doesn't like to keep its oil.

Anyone has an idea?

Quote: Oil sputtering out of the cap which doesn't appear to screw on
like the other one and the oil rebreather going into the carb
http://possy.de/onan1.jpg

After two minutes of running, there is a sizable amount of oil on the
tarmac. http://possy.de/onan2.jpg

--
Best regards

Peer Oliver Schmidt
'76a Eleganza II, CA
'73 Sequoia, VA



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
Re: [GMCnet] Oil sputtering (4K) Onan [message #322377 is a reply to message #322376] Sat, 19 August 2017 20:42 Go to previous messageGo to next message
Olly Schmidt is currently offline  Olly Schmidt   United States
Messages: 1265
Registered: February 2014
Location: Germany and Scottsville, ...
Karma: 8
Senior Member
Matt,

did you ever try fixing the probable cause, ie. the not working breather
hose?

--
Best regards

Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA

'76a Eleganza II, CA
'73 Sequoia, VA


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Best regards

Olly Schmidt
PGP Key ID: 0x18a9 3a1f 4196 bf22
'76a Eleganza II, VA
'73 Sequoia, SH, Germany
Re: [GMCnet] Oil sputtering (4K) Onan [message #322378 is a reply to message #322377] Sat, 19 August 2017 21:14 Go to previous messageGo to next message
Matt Colie is currently offline  Matt Colie   United States
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
Senior Member
Peer Oliver Schmidt wrote on Sat, 19 August 2017 21:42
Matt,

did you ever try fixing the probable cause, ie. the not working breather
hose?

--
Best regards
e
Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA

'76a Eleganza II, CA
'73 Sequoia, VA

Peer,

Funny you should mention that. I thought that this was an indicator of an engine problem.
So, I did a cylinder leak check first.
That was good (pretty good really).
Then I set up to actually measure the crackcase pressure. (I was an engine lab rat for decades.) This was exciting because it alternated between blowing the water out of the manometer and sucking it into the crankcase.
This was at the dipstick/lube oil fill. I gave up on that and put the manometer down stream of the crankcase reed valves.
That was almost disappointing - Nothing there.
With new orifice and a Magnahelic (expensive manometer) I finally got a reasonable blow-by measurement at power required for the A/C, the water heater and the microware (How's that for a load bank?) to be a quarter of a CFM.

Then, the LED in my brain lit (only recently upgraded from incandescent) and I realizsd that the with the engine being an opposed twin, it has to have immense crankcase volume and therefore pressure fluctuations and there is nothing to be done, but live with it.

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
Re: [GMCnet] Oil sputtering (4K) Onan [message #322382 is a reply to message #322378] Sat, 19 August 2017 21:43 Go to previous messageGo to next message
Olly Schmidt is currently offline  Olly Schmidt   United States
Messages: 1265
Registered: February 2014
Location: Germany and Scottsville, ...
Karma: 8
Senior Member
Matt,

thanks for your explanation. Forwarded to my friend, he likes your text :-)

--
Best regards

Peer Oliver Schmidt
the internet company
PGP Key ID: 0x83E1C2EA


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Best regards

Olly Schmidt
PGP Key ID: 0x18a9 3a1f 4196 bf22
'76a Eleganza II, VA
'73 Sequoia, SH, Germany
Re: [GMCnet] Oil sputtering (4K) Onan [message #322384 is a reply to message #322378] Sat, 19 August 2017 22:01 Go to previous message
Dennis S is currently offline  Dennis S   United States
Messages: 3046
Registered: November 2005
Karma: 2
Senior Member
Peer/Matt

Another old thread talking about the pressure generated by the engine design with the cylinders operating on the same cycle.


http://gmc.mybirdfeeder.net/GMCforum/index.php?t=msg&goto=24185&rid=904&srch=Onan+oil+dipstick+blow#msg_24185

Dennis



Matt Colie wrote on Sat, 19 August 2017 21:14
Peer Oliver Schmidt wrote on Sat, 19 August 2017 21:42
Matt,

did you ever try fixing the probable cause, ie. the not working breather
hose?

--
Best regards
e
Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA

'76a Eleganza II, CA
'73 Sequoia, VA

Peer,

Funny you should mention that. I thought that this was an indicator of an engine problem.
So, I did a cylinder leak check first.
That was good (pretty good really).
Then I set up to actually measure the crackcase pressure. (I was an engine lab rat for decades.) This was exciting because it alternated between blowing the water out of the manometer and sucking it into the crankcase.
This was at the dipstick/lube oil fill. I gave up on that and put the manometer down stream of the crankcase reed valves.
That was almost disappointing - Nothing there.
With new orifice and a Magnahelic (expensive manometer) I finally got a reasonable blow-by measurement at power required for the A/C, the water heater and the microware (How's that for a load bank?) to be a quarter of a CFM.

Then, the LED in my brain lit (only recently upgraded from incandescent) and I realizsd that the with the engine being an opposed twin, it has to have immense crankcase volume and therefore pressure fluctuations and there is nothing to be done, but live with it.

Matt


Dennis S
73 Painted Desert 230
Memphis TN Metro
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