rebuilt kohler, still leaks

Discussion in 'Mechanic and Repair' started by 97firebird, Apr 29, 2005.

  1. 97firebird

    97firebird LawnSite Member
    Messages: 41

    Ok, Ive got a 20hp kohler magnum (older motor). This past winter I replaced the pistons, rings, got a valve job, new head gaskets, and reapplied gasket-maker to the base of the heads(these require gasket maker because there isnt any gasket to buy). The engine is still leaking oil from the front somewhere around the back of the carb. I dont understand how I could have all new gaskets in there and still have the thing leak!! I believe I applied the gasket-maker and everything else correctly, so is there something I'm missing here?
  2. KathysLGC

    KathysLGC LawnSite Bronze Member
    Messages: 1,345

    Did you take a good look at the head to see if it was cracked? Did you clean the area before applying the gasket maker?
  3. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    OK 97firebird,Evidently there is we just gotta figure out what !
    I'm gonna assume this is a MV20 because you said behind the carb. instead of under....If I couldn't see where the oil is coming from I would remove all the cylinder shrouding and top blower housing degrease and clean it,blow it dry and start it up with them off being careful not to get too close you can let it run for 8 to 10 minutes without harming anything. shut it off and look for your leak.
    It could be the top crank seal leaking down behind the carb. ?
    I don't know how you cleaned the old sealer off your cylinder jugs but never use a gasket scraper or pocket knife, They will put scratch marks in the aluminum which may be a little hard to seal, Use a wire wheel in a drill to clean sealer off.
    Whenever you find the leak you will know what to do to fix it.

    14yr. Briggs & Stratton Master Service Technician
    Kohler Factory Trained
    Factory Trained Polaris ATV & Watercraft
  4. 97firebird

    97firebird LawnSite Member
    Messages: 41

    ok guys, The cylinder heads were acid washed and cleaned by a machine shop and I cleaned the base of the case with extreme care. I am about 99% sure that there is no oil leaking from the heads. This is what I have determined so far...when the cylinder heads were cleaned at the shop they told me that I would have to re-hone the cylinders, so I borrowed a tool and did it by hand. However, I have never had experience with honing before so I am not sure how great it came out...The other thing is that I was reading in the service manual was that if the cylinder size is not within a certain spec of the size of the piston, problems could occur. I have determined that the oil is building up around the valve covers, and a ton of oil is getting blown out of the EGR system because the top of the air cleaner plate is a puddle. So here are the possibilities: 1) Cylinder out of round 2) cylinder not correct bore size for stock size piston 3) bad hone ...Let me know what you think, or if there is anything else that could cause excessive blow-by. Thanks
  5. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    There is a couple things to check before you tear back into it.
    Take both valve covers off and check the small oil return holes in the bottom of the chamber,Take a small wire and make sure they are open. Take the cover with the breather hose and flip it up side down there is a hole with a brown looking disk covering it,lightly push down on it and it should spring back up (now it wont move much ) But it must have a springy feel. If it doesn't replace the assembly,I have seen these cause your problem.
    If thats fine its time to recheck your cylinder bore.
    I would remove the heads first and rotate the piston to the bottom,Use a inside micrometer and measure the bore in a X pattern quarter inch from the top and down at the piston write these mesurements down and go to your service manual. It will give you the bore specs. then compare.
    If you don't have the micrometer take the jugs off,Remove your compression and oil rings and one at a time put them in the bore quarter inch from top and measure the gap with a feeler gauge write it down and slide the ring to the center of the bore and measure then about a half inch from the bottom.
    That will show you bore taper and ring end gap spec. go to the manual for ring end gap spec. If the gap is wider than spec. you gotta do a bore job and replace pistons.
    Let me know how it turns out.
  6. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    If you remove the jugs pay close attention to the rings , the gaps could have aligned them selfs up.
  7. Oldtimer

    Oldtimer LawnSite Bronze Member
    Messages: 1,459

    Did you use new head bolts?
  8. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    Just for the Record Kohler put out the head bolt update on the Command series engines It doesn't apply to the Magnum or K series engines.
  9. 97firebird

    97firebird LawnSite Member
    Messages: 41

    ok, thanks guys. I'll let you know how I make out. i already took the heads off today and there was a ton of oil on top of the pistons, so obviously there is something funky. Thanks Again.
  10. General Grounds

    General Grounds LawnSite Senior Member
    Messages: 902

    :blob3: are you sure the breather is functioning?

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