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wndshldgoes · 01-19-2015, 04:57 PM

While doing maintenance on my Onan Microquiet 4000 today, the air filter was saturated with oil as well as the lower part of the filter case and lid. Has anyone experienced this same issue.
The generator started easily to warm up the oil before draining. It was at the full mark on the dipstick before starting. After cleaning out the oil from the filter housing and adding new air filter and filling oil to proper level.

Contacted Onan/Cummins Tech Support and they referred me to my local dealer to help with the issue. Sorry but past experience lets me know not to take it there.

Let me know if you have seen this issue and what you think may have caused it.

BFlinn181 · 01-19-2015, 05:40 PM

The oil is most likely from the crankcase vent hose that connects the crankcase to the air filter. There might be a small leaf valve at the crankcase that is supposed to keep oil from coming out with the pressure from ring blow by and usual crankcase gases. There is not PVC valve like an automotive engine. You could replace the leaf valve, if the pressure is really bad you'll have to rebuild the engine. You might do a compression test to see the condition of rings and valves.

wndshldgoes · 01-19-2015, 06:17 PM

Bflinn, thanks for the info. Will check that valve and see if there is any oil in the filter from the 30 minute load run of the generator today. The motor didn't sound like it my need rebuilding, so the valve may be sticking. Generator only has 500 hours on it.

dvmweb · 01-19-2015, 07:16 PM

Would overfilling cause this?

2013 FleetWood Expedition 38B

BFlinn181 · 01-19-2015, 07:48 PM

Quote:

Originally Posted by dvmweb

Would overfilling cause this?

2013 FleetWood Expedition 38B

Perhaps, could also be clogged drain ports in the block allowing oil to back up. There are many reports of oil in the air filter of Onan generators, mostly 4000 model like the OPs. Most solved with replacement of the leaf valve.