Oil in the air filter (Onan 4000)

[CharlieTwo]

I am getting oil in the air filter on my Onan 4000. What would cause this and where can I get (best place) a service manual for it. I am running 30wt in it right now.

[Dave78Chief]

The Onan 4.0BGE generator crankcase ventilation system hose connects to the base of the air filter to carburator adaptor plate in order to recirculate crankcase vapors through the carburator intake. This hose connects to the valve cover on the backside of the engine. There is baffle, reed valve, and filter under the valve cover that could be getting weak allowing excess oil to be recirculated. It could also be due to worn or broken piston rings allowing excessive blow by (check by performing a compression test)

Get the spec number of your generator then use this page to determine the Onan manual number you need:
http://www.autocd.com/Onan2.html

The RV Genset section is about 2/3 down the page.

You can get manuals from Onan, Ebay, or numerous RV dealers. Just google them.

Dave

[CharlieTwo]

Thank you very much Dave. I will check that out.

[Hikerdogs]

Quote:

Originally Posted by Dave78Chief The Onan 4.0BGE generator crankcase ventilation system hose connects to the base of the air filter to carburator adaptor plate in order to recirculate crankcase vapors through the carburator intake. This hose connects to the valve cover on the backside of the engine. There is baffle, reed valve, and filter under the valve cover that could be getting weak allowing excess oil to be recirculated. It could also be due to worn or broken piston rings allowing excessive blow by (check by performing a compression test) Get the spec number of your generator then use this page to determine the Onan manual number you need: http://www.autocd.com/Onan2.html The RV Genset section is about 2/3 down the page. You can get manuals from Onan, Ebay, or numerous RV dealers. Just google them. Dave

You might also want to contact Onan with your model and serial number. They sent out a new baffle/valve kit for some models to avoid just the problem you are having. I installed the kit on our 5,500 watt model and haven't had any problem with oil in the air filter element since the installation.