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Onan Help Or Advice...


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#1 CASENUT OFFLINE  

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Posted June 30, 2012 - 10:45 PM

I have a 16 HP onan that I basically 'rebuilt', I had to rip it all down and put in a new rod due to the fact that the old one broke. Well I took all the measurements and it all looked real good. Engine starts and runs perfectly. However....

I got to thinking about the Rod, and why it would have broken...I remembered that I had not swapped out the oil filter...which IMHO could impede oil flow and may have been the cause for the 'broken rod', so I pulled the old filter out. The oil in the filter did not look like the brand new oil that I put in the crankcase...and there was not 'a lot' in there as in it was not 'full' of oil.

It was kind of runny and soupy. so I got to wondering how do you verify oil pump output once the engine is installed I would like to take the tractor and do some mowing with it...but will not risk my freshly rebuilt engine until I know for sure...

Thanks...

#2 MH81 ONLINE  

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Posted June 30, 2012 - 11:20 PM

Jim, page 7 of this manual: http://gardentractor...ce-w-opt-parts/
Talks about inspecting the bypass valve. It also shows how to remove the pump, but it doesn't talk about testing for pressure.

I'll keep reading.
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#3 MH81 ONLINE  

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Posted June 30, 2012 - 11:25 PM

Page 34 shows a parts drawing. The pump looks to have a port on top of it with a pipe plug in it. A quick scan of the manual doesn't mention it. I wonder if that's your test point or is that a check valve? It does say 30 lbs pressure is optimum, so there has got to be a test point somewhere???

Sorry I'm not more help, never owned one.
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#4 CASENUT OFFLINE  

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Posted June 30, 2012 - 11:47 PM

Jim, page 7 of this manual: http://gardentractor...ce-w-opt-parts/
Talks about inspecting the bypass valve. It also shows how to remove the pump, but it doesn't talk about testing for pressure.

I'll keep reading.


Thanks, I've done a bit of reading as well...and will continue appreciate your time and efforts. all the manuals I have read do some verification during the build process, and one indicates 8lbs of oil pressure ...however with no oil pressure gauge? I was thinking about just removing the filter and cranking it...surly if the filter is getting oil then...you have pressure and you have flow...if however the filter is not getting oil...then...out comes the engine...yuk!

#5 KennyP ONLINE  

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Posted July 01, 2012 - 04:52 AM

Just above the oil filter should be a 1/8" pipe plug to hook a gauge to. This pic is from the manual above.
BF Oil Filter.jpeg
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#6 Toolpartzman OFFLINE  

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Posted July 01, 2012 - 05:19 AM

Some had NO filter and some with the arrangement as Kenny shows above. Mine was a tap in the casting. Some had a cover plate which would provide for adapting a filter and each had the 1/8" tap.

I'm curious about the broken rod. In my one and hopefully last experience with the 16H Onans, those rods were impressively stout. My engine was knocking and smoking, but running. At teardown, the #2 rod to crank face was severely worn.Lots of sideplay, and wear on the rod as well as .026 gouges in the crank. Even with all this the rods were intact. For one to actually break, IMO means oil starvation over a long period

I'm not certain whether your filter has a bypass or not, but if the filter or the crankcase is low on oil, then the oil pump will be oil-starved also.

Since engines seem to like oil to keep from eating themselves,it sounds like yours had quite a buffet before it quit and whatever steel and aluminum shavings resulted are still there and the old filter has lots of 'em.

--Which rod broke? #2 is the last to get oil
--IMO when you rebuild an engine and install the same filter, you are likely to get to do it again.

Edited by Toolpartzman, July 01, 2012 - 06:07 AM.


#7 KennyP ONLINE  

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Posted July 01, 2012 - 06:38 AM

On any engine with an oil pump, any rebuild after a failure would require a complete oil system cleaning to remove those fine shavings. I had a Chevy 350 that I rebuilt. Had the block vatted, cleaned?, and new cam bearings put in. I put it together and promptly had a rod knocking and very little oil to the valve train. The idiot had failed to flush the oil passages. Took it elsewhere to be done right. Had to buy a new crank, rod, and cam bearings.

#8 olcowhand ONLINE  

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Posted July 01, 2012 - 09:14 AM

I usually install a pressure gauge kit on mine, but on those without the gauge, I use a long piece of 1/8"npt pipe, say about 8" long, and screw this into the port, then screw a gauge onto the pipe to test. The oil pump regulator is designed to bypass at 35psi, but will only get this pressure cold. I set my regulator to where I have 20psi at full rpm's hot. The 8psi is hot idle minimum.
The regulator is nothing more than a spring with a regulating pin. The bolt simply tightens to the block & pushes against the spring. I just find a longer bolt, usually have to make it by threading a longer bolt further down it's length. I thread it far enough to allow for a locknut. This way I can adjust later if need be to raise the pressure as bearings wear.
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#9 CASENUT OFFLINE  

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Posted July 01, 2012 - 09:52 AM

hmmm, lots of great ideas, glad I considered it before it was to late...thx everyone for input! as for cyl it is the one that points to the left when in drivers seat

#10 CASENUT OFFLINE  

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Posted July 02, 2012 - 07:39 PM

all was fine I was just paranoid...

#11 olcowhand ONLINE  

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Posted July 02, 2012 - 08:00 PM

all was fine I was just paranoid...


Good deal! Better safe than sorry anyway!

#12 Toolpartzman OFFLINE  

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Posted July 02, 2012 - 08:32 PM

On any engine with an oil pump, any rebuild after a failure would require a complete oil system cleaning to remove those fine shavings. I had a Chevy 350 that I rebuilt. Had the block vatted, cleaned?, and new cam bearings put in. I put it together and promptly had a rod knocking and very little oil to the valve train. The idiot had failed to flush the oil passages. Took it elsewhere to be done right. Had to buy a new crank, rod, and cam bearings.

:mad2: :mad2: :mecry:

#13 KennyP ONLINE  

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Posted July 02, 2012 - 09:04 PM

This time, Lee, it came back balanced too! :bounce: :dancingbanana: :orangecool:

#14 MH81 ONLINE  

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Posted July 02, 2012 - 09:12 PM

Wow, Kenny, that's a darned shame.
I will tip my hat to you that didn't have a creative storage location suggestion for the parts you had to replace.

#15 KennyP ONLINE  

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Posted July 02, 2012 - 09:57 PM

I've got about $1500 dollars in that short block, before I added the other goodies!. It pays to clean those oil passages!




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