Small Engines (Lawn Mowers, etc.)/Kohler CV15S Burning Oil


I have a John Deere LT150 tractor with a Kohler CV15S engine. It recently started puffing blue smoke (oil) intermittently, mostly when under load. Especially with the mower deck engaged. The engine has to be fully warmed up. I thought I might have a blow head gasket so I replaced that this past weekend. I didn't see any evidence of a blown head gasket. I also cleaned the carburetor thoroughly. I noticed what I thought was an excessive amount of oil from the PCV tube going into the carburetor intake. After the head gasket replacement it ran fine for about 15 minutes and then started belching blue smoke again only worse than before. Should I be looking for a broken oil ring or compression piston rings? I didn't notice any cylinder scuffing when I had the head off. Could the head get pressurized and force oil past the valve seals?

Yes, the engine can get pressurized.

Did you download the engine service manual from Kohler's website?

You really should perform 2 tests:

1) Crankcase vacuum test.  Make sure the engine is creating and maintaining vacuum so the crankcase does not push out oil.

2)  Leakdown test.  Checks the condition of the cylinder, piston, rings and make sure there is no excessive loss due to worn parts.

What weight of oil are you using?

Did you torque the head?


Small Engines (Lawn Mowers, etc.)

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Eric A. Jones


Lawnmower Repair . Certified Master Service Technician from B&S. Have 23 years experience on B&S, Lawn Chief, Weed Eater, Echo, Peerless, Wheel Horse, Snapper, Atlas, MTD, McCulloch, Homelite and many other numerous brands. Specialize in electrical repair.


Born and raised in the midwest. Started tinkering with engines when I was about 14 on my Suzuki RM-80. I began lawn mower repair at a small hardware store. I knew absolutely nothing. I read lots of repair manuals and met an older fellow who taught me many lessons. I continued working on small engines through high school and paid my way through college working on mowers at the same hardware store. Decided to get away from the midwest and mower repair so I joined the Air Force. I repaired air traffic control electronic equipment and ended up in Hawaii where I got a part time job at Small Engine Clinic. I gained a lot of experience from the Small Engine Clinic and had a blast repairing small engines. I then took the Briggs and Stratton Master Service Technician test and earned my MST. I then traveled to Wisconsin where I attended the factory update training seminar and received formal training. Continued working on mowers part time as I completed 20 years of military. Retired from the military on a Friday and continued in the lawn and garden industry the next Monday.

MAS Aerospace Operations BA Mathematics AAS Electronic Communications AAS Electronic Technology

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