Excessive oil consumption, oil leaks at exhaust gasket

Discussion in 'Mechanic and Repair' started by hibby, Jun 23, 2004.

  1. hibby

    hibby LawnSite Member
    Posts: 4

    There have been similar posts to this problem but not exactly the same. This is on a grasshopper mower with a Kohler Command 18 HP horizontal shaft engine. It isn't mine either, it is a friends.

    Background info. At the end of last year, somehow the valve seat insert came loose (not sure which valve). So, in February, he just bought all new parts. New head, valves, rockers, and push rods. Reused the same lifters. Keep in mind that this is only on one side of the V-twin, he did not even touch the other side. New gaskets and seals. He put everything together and the machine ran great. Then about a month ago, it started using a lot of oil, about 2 quarts every 6 hours. Then about 2 weeks ago he went to mow and when he put the machine under load, it died out. When he restarted it, it ran fine at an idle except it smoked like crazy. He then noticed that oil was oozing out of the exhaust where the short tube bolts up to the head (right through the gasket).

    The first thing I thought was to check the breather. Well, I actaully haven't pulled it out yet, but I looked in the air intake just above the carburetor and there is a little bit of oil there, but not much. Not enough to look like 2 quarts went through it in 6 hours anyways. In addition, the leak is only coming out of the side that he rebuilt the head. The other side is dry. I also pulled the plugs and the side that he did not touch, the plug looks normal. It's dry, clean, and looks good. The side he rebuilt however is a different story. It was caked up so much with what I assume is carbon (it isn't all black, it has some grayish color to it mixed in with black carbon) that you couldn't even see the electrode on the plug. It was just one big glob of hard crusty substance.

    So, I am guessing that the breayther is not the problem. Otherwise both sides should have shown signs.

    The next thing I thought was that they damaged the head gasket while instaklling the head. So I took the head back off and was amazed at how much buildup there was on the piston and the head. I bet the buildup on the piston is about 1/4 inch thick. It's really bad.

    I removed the valves from the head, and the back of the intake valve (on the head, not up the stem) has burnt oil accumulated on it. The exhaust valve also has some buildup but it seems lighter and more completely burnt, which makes sense. The head gasket did not show any signs of damage.

    I also measured the head out and there is not an excessive amount of clearance between the valve stem and guide (about .001") which I didn't figure there would be since they were both new in February. The oil seal on the intake valve also appears OK, no visual signs of damage and seems to have a good fit on the valve stem and a real good grip on the guide that holds it in place.

    So my question(s) is...Have I exhausted all possibilities on the top end? Is it still possible that the oil is coming in through the intake, breather, valves, etc? Or, should I clean everything up, put it back together, and then perform cylinder compression tests, leak down tests, etc? (I know I probably should have done that in the first place, I just started assuming stuff once he told me he rebuilt the head this past winter).
     
  2. shopbytch

    shopbytch LawnSite Member
    Posts: 37

    Kohler says a well maintained engine will need a valve job at 1000 hrs. and would need a rebuild at 2000. The engine could have overheated and warped on that head which the rebuilder didn't correct. I've seen this on a few kohlers and the valve job didn't last. A rebuild takes a long time and dedication and you still have an old engine; so it's cheaper to get a new one. Thicker oil and plug cleaning is all you can do. Now if you're gonna donate that engine to science, force it to run a few hundred rpms higher under load, which will overheat the combustion chamber and keep it clean.
     
  3. hibby

    hibby LawnSite Member
    Posts: 4

    Good point. The engine has about 1400 hours on it.
     
  4. shopbytch

    shopbytch LawnSite Member
    Posts: 37

    I think that it already paid for itself :)
     

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