Kohler Pro 25 HP Valve Cover leaking

jakesmurray

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The right side valve cover on my 25 HP Kohler is leaking badly. We replaced the gasket (o-ring Kohler calls it) with an OEM one, but it still leaks oil like crazy. The new gasket was very difficult to get down into the groove into the valve cover, has anyone else had this problem? Also, the cover itself is plastic, could it be warped? Thanks.
 

ILENGINE

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warpage and cracking have both occurred
 

jakesmurray

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Ok, I found out what my problem was. I hope my findings help some people in the future...

It turns out that Kohler redesigned the valve covers on these engines in July of 2004. My particular engine had one of the original covers on the left side, and a newer style cover on the right side. Instead of using a gasket on the newer cover, they put some red goopy sealant on it, and it leaked. It turns out that the gaskets for the old covers and new covers are different and are not interchangeable. I picked up a valve cover kit for the left side which includes the cover, gasket, and screws. Then I picked up another single yellow gasket, which fits correctly in the right side cover I already had. So now I have the newer style valve covers and the good yellow Teflon coated gaskets. Hopefully no more leaks. Here is the Kohler parts bulletin explaining all of this:

View attachment Kohler Parts Bulletin No. 240.pdf
 

Snwmblman

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couldn't open the link do you have the part numbers for the new cover and gaskets? I really don't want to use the rtv sealant
 

Scrubcadet10

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"warpage and cracking have both occurred"
Usually happens with age Ilengine :laughing::laughing: :wink:

"couldn't open the link do you have the part numbers for the new cover and gaskets? I really don't want to use the rtv sealant"
from the PDF link

Two different valve cover/O-Ring design combinations
have been used on Command Twin Cylinder engines.
Due to differences in the O-Ring groove, it is critical to
match the correct O-Ring to the valve cover being
serviced, in order to seal properly and prevent leakage.
Prior to July of 2004, the valve covers were secured
with shoulder screws, or a combination of loose
spacers and M6 hex. head screws. See Figure 1.
These covers use a Black O-Ring, Part No.
24 153 23-S. In order to eliminate the loose spacers
and screw variations, the newer valve covers have
integral compression limiting spacers and are all
secured with M6 hex. head screws. The O-Ring groove
in these new covers is slightly deeper and narrower. A
new Brown (Part No. 24 153 29-S), or Yellow (Teflon®
coated, Part No. 24 153 28-S) O-Ring, has been used
in production with these covers. See Figure 2. Although
functionally interchangeable, to ensure best fit and
performance the Yellow (Part No. 24 153 28-S) O-Ring
is preferred and should be used when servicing. As
standardization, all future service/parts requirements
from the factory for the Brown (24 153 29-S) O-Ring will
be filled with the Yellow (24 153 28-S) O-Ring.
Although the O-Rings are similar in overall shape they
are not interchangeable. Installation of the wrong
O-Ring will result in leakage and not be warranted.
 

ILENGINE

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Warpage and cracking of the cover?

Yes. Even occurred on new engines. Part of it was due to over torque of the cover screws. Some had issues with the bolts corroding to the aluminum head leading to broken cover bolts. The covers are designed to float but due to various issues sometimes it didn't work,
 
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