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Old 08-10-2011, 07:20 AM
TJJohnson TJJohnson is offline
LawnSite Member
Join Date: Aug 2011
Location: Detroit, MI
Posts: 9
!!!Oil Evacuated Crank Case in 15 Seconds -- 2004 Kohler Command Pro 23 hp

Hi Folks. I could use some help root causing this issue I'm having with my mower. It's a long story but Iíll start from the beginning anyways. I appreciate your input...

I bought this house on 10 acres and was pleased to be able to negotiate the mower into the deal. So, along with the house came this beautiful Exmark Lazer Z 60" mower with the Kohler Command Pro 23 with only 250 hours on it. The home-owner's son even gave me a walk-through on how to start the mower and drive it, etc, since I have never driven a zero-turn mower before. The mower started right up and drove perfectly with no apparent issues whatsoever. The thing seemed like a brand new mower and I was actually looking forward to mowing my new lawn!

Well, then a few weeks went by and we finally got the keys to our new home. Of course, the first thing I did was jump on that mower (after a brief study of the machine's architecture) and fire it up! It started without hesitation. Beautiful! Well, then I deactivated the choke valve, grabbed the handles, put them together, and slowly pushed them forward. STALL! The engine stalled on me! I tried it again, and the engine stalled again! Hmmm, I took another quick study of the machines architecture and immediately noticed the parking brake. DOH! Started it up for a third time, disengaged the parking brake, put the handles together, slowly pushed them forward, beautiful! I zipped up the hill at full throttle!

Well, then the fun began! About 10 seconds later I noticed the smell of burning oil, only to look behind me to find oil spraying from the drive belts and up into the exhaust! I cut the engine and did a quick inspection and saw that oil was dripping from the entire top of the engine! I quick dipstick check showed a tiny bit of oil left in the crankcase but enough to keep the engine lubed so I could drive the machine back to the barn (of course with more oil gushing from all over the top of the engine). AAAAAGH! My dreams were shattered!

Well, then the troubleshooting and root cause analysis began. The next day, starting from the top, I took off the air cleaner and the plate below it so that the choke valve was exposed. I put a quart of oil into the crankcase and fired up the engine (it started right up again!). I let the engine idle for a few seconds while I inspected the engine and saw that the oil was gushing from the crevice between the left hand (the side without the oil fill cap) rocker cover and the baffle plate.

Next, I cut the engine and removed the rocker cover where the oil appeared to be coming from. Everything seemed ok with the press-in-place rubber seal and this did not appear to be the issue.

Then, I blew air into and sucked air out of the breather hose that comes from the breather plate and directs the crankcase gas into the choke valve. Air seemed to be flowing easily through this tube in both directions, but it tasted gross! Well, I guess it didn't taste THAT bad. But this definitely indicated to me that the crankcase was vented properly and that the oil leak must be due to over-pressurization of the crankcase. Throw in the towel for the day.

The next day, I really ripped into it. Removed the exhaust and saw and oily residue on the exhaust port of the left hand chamber. DOH! Now I'm thinking that the issue is a piston, rings, or an exhaust gasket! Kept going. Removed the carb, then had to shimmy the front plastic grass shield off to get the baffles (above the rocker covers) off. Then I saw something interesting!

The breather valve gasket was blown out on the side adjacent to the left hand head (the side where the oil was coming from)! I removed the breather plate and noticed that this was actually a high pressure oil passage! YAY! This should be easy! It appears that I just need to replace this breather cover gasket! Or is this really all that is the matter?

So this is where I am at as of last night. My tentative plan is to go to Weingartz, pick up the gaskets I need and some tune up parts, reassemble the engine, and fire it up! But, I'm still wondering why I would've blown out this gasket? Did the multiple stalling of the engine cause some sort of over-pressurization of the oil gallery? Or, was it actually crankcase pressure that increased that blew out the gasket? Why would there be high crankcase pressure and why was I burning oil on the left hand cylinder?

Hmmm, something is telling me that if I just reassemble, I'm going to blow out the gasket again...

Well, if you made it this far, maybe you could spare some advice? This site was referred and highly regarded by a colleague of mine in the automotive engine engineering as well as the commercial lawn care business!

Many thanks,

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