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Old 22-07-2013, 09:04   #1
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Oil Leak Where Bell Housing Bolts to Engine...

I've discovered a small oil leak at dead center bottom of where the bell housing bolts to the engine. There seems to be small hole allowing a drip or two every 10 minutes of engine operation. The engine is a 45 hp Kubota. Any idea what is up in that area that could be causing the leak? Taking apart the transmission and bell housing is a major pain, so I'm hoping to get some ideas on what may be going on before I attempt any exploratory surgeries.

Cheers- Matt
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Old 22-07-2013, 09:15   #2
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Re: Oil leak where bell housing bolts to engine...

Suspect rear main engine oil seal has begun to leak, if it is engine oil that is leaking, not tranny fluid.

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Old 22-07-2013, 09:18   #3
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Thanks. Definitely not ATF.
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Old 22-07-2013, 10:04   #4
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Crankshaft lip seal
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Old 22-07-2013, 11:07   #5
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Re: Oil leak where bell housing bolts to engine...

Make sure the crankcase breather has no obstruction that can cause pressure in the crankcase to go up and force oil out. This pressure can be so high that it will force the oil dipstick from its seat.

If the engine is old, the rear main bearing seal can get hard and leak. Seal softener can be purchased and should take care of the problem for several more years.
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Old 22-07-2013, 11:59   #6
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For SOME engines set to an angle, the oil level ends up too high on the rear main seal and running with a bit less oil than "full" on the dipstick can slow or end the leak
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Old 22-07-2013, 12:08   #7
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Re: Oil leak where bell housing bolts to engine...

Yep, sounds like a rear main, or possibly the back of the oil pan.
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Old 23-07-2013, 18:31   #8
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Re: Oil leak where bell housing bolts to engine...

Had the exact same problem on my Universal M-50 (Kubota block). Took it apart and replaced main engine seal...still leaked. After $800 of mechanic visits, pulled the fuel injectors and had them pop tested. Three were bad. Sent them off to rebuild and after re-installing them, the leak disappeared. If you haven't had your injectors checked, this would be a cheap diagnostic. Good luck.
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Old 21-08-2013, 18:09   #9
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Re: Oil leak where bell housing bolts to engine...

Just a quick update: Had the rear main seal replaced. Parts were $55 and it took a mechanic about 4 hours to complete the job. So far, no more leaking oil...........
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Old 22-08-2013, 05:36   #10
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Originally Posted by jimking100 View Post
Had the exact same problem on my Universal M-50 (Kubota block). Took it apart and replaced main engine seal...still leaked. After $800 of mechanic visits, pulled the fuel injectors and had them pop tested. Three were bad. Sent them off to rebuild and after re-installing them, the leak disappeared. If you haven't had your injectors checked, this would be a cheap diagnostic. Good luck.
What was the relation of bad injectors to an oil leak. Fuel dilution? Over full crankcase? Fuel leak? Plugged crankcase vent found while changing injectors?
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Old 30-08-2013, 20:34   #11
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Re: Oil Leak Where Bell Housing Bolts to Engine...

Sorry for late response....good question. I am not an expert but I believe that the cylinders were not firing and fuel was leaking from the pistons through to the crankcase and causing excess mix in oil. The overfill oil was bypassing the rear engine seal (I think) and then leaking out the bottom vent in the bell housing. Good luck.
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