Home » Public Forums » GMCnet » [GMCnet] Oil sputtering (4K) Onan
| [GMCnet] Oil sputtering (4K) Onan [message #322345] |
Sat, 19 August 2017 12:36  |
Olly Schmidt
Messages: 1265
Registered: February 2014
Location: Germany and Scottsville, ...
Karma: 8
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Senior Member |
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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
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| Re: [GMCnet] Oil sputtering (4K) Onan [message #322350 is a reply to message #322345] |
Sat, 19 August 2017 13:30  |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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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 12:36Morning,
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
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| Re: [GMCnet] Oil sputtering (4K) Onan [message #322351 is a reply to message #322350] |
Sat, 19 August 2017 13:34 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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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 13:30Peer
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 12:36Morning,
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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Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: [GMCnet] Oil sputtering (4K) Onan [message #322376 is a reply to message #322345] |
Sat, 19 August 2017 20:34 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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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 13:36Morning,
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
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| Re: [GMCnet] Oil sputtering (4K) Onan [message #322378 is a reply to message #322377] |
Sat, 19 August 2017 21:14 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Peer Oliver Schmidt wrote on Sat, 19 August 2017 21:42Matt,
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
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| Re: [GMCnet] Oil sputtering (4K) Onan [message #322384 is a reply to message #322378] |
Sat, 19 August 2017 22:01 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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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 21:14Peer Oliver Schmidt wrote on Sat, 19 August 2017 21:42Matt,
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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