rebuilt kohler, still blowby

Discussion in 'Mechanic and Repair' started by 97firebird, May 10, 2005.

  1. 97firebird

    97firebird LawnSite Member
    Posts: 41

    Ok guys, here I am again..I posted not too long ago saying how I rebuilt my kohler magnum (92-93 model) anyway, i put new pistons, rings, cylinder hone, valve job, replaced bad valves, new gaskets..the whole thing. There is still a lot of oil getting blown past the rings somehow through the breather system and up into the air filter. There must be a reason for excessive positive crankcase pressure or something because the cylinder bore and rings are brand new and i had the guy at the shop make sure the cylinder was not oversized for a stock sized piston. Therefore, why am i getting excessive blowby and leakage out of the breather valve cover? I believe the breather is working correctly, not clogged either, and is installed correctly, is there anything else that can cause this? Could it be valve guides/seals? This motor has been torn apart three times already trying to fix the problem and I am ready to light a match! Any help would be greatly appreciated. Thank You.
     
  2. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,022

    It still sounds like a breather problem,I see now your mag. has a different style breather than i mentioned in your last thread. If you havn't done so take the breather assembly apart, Inside you will find a umbrella valve part# 52-462-01 and a hose type seal part# 52-032-04-S Replace both these with new gaskets part# 52-055-01-S . Post me your full model & spec. numbers and I will check for any old service bulletins for this problem.
     
  3. 97firebird

    97firebird LawnSite Member
    Posts: 41

    Model # is MV20S
    Spec # is 57520...(cant read rest)
    Are you saying that the valve could be bad or that cylindrical gasket/tube could be no good? The valve just consists of a hole in the plate with a plastic flap sitting over the top of it. When I pull it away from the hole and let it go it snaps right back. Doesn't seem like there could be much that goes wrong with it. You could be right, but I dont want to keep replacing parts and not fixing the problem. However, i appreciate the assistance.
     
  4. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,022

    I'm sorry I havn't helped you solve this problem yet. Had I been able to see or touch this engine I'm sure the problem would be solved by now,But all I can do is give you my thoughts as to what could cause this problem.
    I did find a service bulletin on this spec. engine,But I must download Adobe Reader on my computer to read it I will do this later tonight.
    In the mean time I went to the good old service manual and went to trouble shooting and the only thing I don't think has been checked is the muffler.
    The baffles break loose from vibration it could restrict the exhaust flow and cause this problem.
    There isn't anything I hate worse than letting a engine problem get the best of me,I will keep trying if you like or I'll give up.
    Soon as I read this bulletin I'll post back if you like !
     
  5. 97firebird

    97firebird LawnSite Member
    Posts: 41

    I am very happy someone is trying to help me out, so thank you...I didn't mean to negate your inputs, but I am trying to get as many possibilities as possible so that I can weed them out. Today I was told by a mechanic that it is probably the pressure release valve. well, this is simply a ball held against the bottom of a hole within the crank case by a spring. So, i pulled the motor once again, pulled the oil pan off, and looked at it...the only thing i can see wrong with it is that the spring has got some nicks and marks in it. Other than that, we blew air through it and it didnt seem to be clogged with anything. The same mechanic also said that it could be the valve seals leaking oil into the cylinders. I think that I am going to have to get a leak down test done. This will atleast tell me where the oil is comming up from. My worries are that I am going to replace those and it wont solve the problem. Then there is the other question as to whether or not there is too much positive crank case pressure causing excessive blowby...but what else would cause this besides a faulty breather system or oil pressure release valve? Beats me. Thanks again.
     
  6. 97firebird

    97firebird LawnSite Member
    Posts: 41

    oh yea, as to the muffler...i blew through it with my mouth once before and it flowed well, so I think I am all set there.
     
  7. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,022

    Maybe This will do it.
     
  8. 97firebird

    97firebird LawnSite Member
    Posts: 41

    This shows the way I have it set up, but I am wondering if there is a new style newer that the reed style valve I have...I am thinking I might as well just replace the entire system just to make sure.
     
  9. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,022


    If there was a even newer style it would have came up on the S. B. web site they post all on there. I like the idea of a cylinder leak-down test, I didn't say anything about it because the average person doesn't have the proper equipment to perform this test but it would tell the whole story as to how things went together. Please keep me posted as to what the outcome is.
    SEE YA !
     
  10. 97firebird

    97firebird LawnSite Member
    Posts: 41

    ok, i am waiting on a crankcase pressure relief valve and new valve seals...I have already bought the new breather valve and tube gasket. Once I get the valve seals I am going to bring the motor down to the shop and get the leak down test done. I am pretty sure it is going to reveal that the valve guide seals are going to be shot. Therefore, the motor will already be at the shop and I'll just have them replace the seals. If not, everything else that could be the problem should be taken care of when I put it back together one last time. I will let you know how it turns out. Thanks for all your help.
     

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