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View Full Version : Kohler CH23S - Shortblock early failure


timberattler
09-09-2010, 02:43 PM
I recently purchased a CH23S Command shortblock to replace the one on my Toro Z253. I've replaced several engines in my 24 years of mowing/small engine mechanic career (any of us who mow wind up becoming small engine mechanics.) I don't use the oil press kill switch on my engines, i always mount an oil pressure gauge so i can keep an eye on the pressure. Initailly i had 38-40 psi when turning 3650 rpms, but after merely 3 hours it had dropped to 20....I called the dealer where i bought the engine and informed them, they said to keep an eye on it and keep running it. When i checked the oil, it was already black with a grey haze (floating metal) and i let them know the oil color and my immediate concern. Engine was purring, no smoke no leaks - full power. After 3 more hours the pressure had dropped to 5 psi and i tool the mower in to their shop. They had a mechanic (per instruction from the area kohler rep) hook up an oil pressure gauge to where the filter connects, and it registered 38psi. I complained saying i know the oil pump is working, but there IS something wrong or that pressure would be making it to the oil pressure port. They said run it. 3 hours later the front seal gives and oil its being liberally distributed via the blower on the flywheel. I called them and they told me to bring them the assembled engine, they'd order a new shortblock and have their mechanic build it.
So they call me today and say they won't be honoring the warranty as it was my fault. They say the magnets in the flywheel came off (keep in mind when get a shortblock you reuse your flywheel and stator) and caused the crank to chew through the crankcase....i know i laughed out loud too. ANy way for those of you guys who know engines, i am including a picture to show the shoddy chamferring job to crankcase oil galleys. My theory is the crankcase was improperly machined, causing oil problems/bearing failure (by the way kohler doesn't use bearing in their engines and you can't buy a new crankcase, only a miniblock or a shortblock) and when the crank cut deep enough through the crankcase, the stator met the magnets.

Look at this photo...does it not look like a machining defect to y'all?

piston slapper
09-09-2010, 03:30 PM
Without more pics, its hard to make the call...
The striping in the top bushing is from a lack of oil (metal transfer) . I'd like to see the crankshaft bearing and rod surfaces. This looks like the top of the engine was starved for oil ( 5 PSI ) . The oil in this engine goes from the oil pump to the filter to the top bushing, and then to the rods. I've seen the welch plug in the crank come loose and cause a similar failure.
If the oil pickup tube fell off it would do the same thing..
Without pics , its all speculation...

timberattler
09-09-2010, 03:42 PM
This is a horizontal shaft engine, the groove is cut in the crankcase "bearing". The kohler horizontal shaft has no bushing or bearing between the crank and the crankcase, so the oil channel on the crankshaft cut into the case on one side producing the "raised" ridge between the oil galleys. My question lies in the machining done to the oil galley holes...it lookslike they were cut in with a chainsaw, not a die grinder. The crankshaft being much harder than the case, has no visible scarring, its still a mirror finish.

piston slapper
09-09-2010, 04:30 PM
Those holes are normal . they were milled out before the bearing surfaces were polished.
I know which engine you have, The area of the engine you are looking at is not the source of this engine failure.
If you can post more pics, I might be able to give you some real answers.

PISTON SLAPPER
Certified Kohler Expert since 1999

timberattler
09-09-2010, 04:45 PM
I'll take some more pictures to post when i get back to my shop. What do we pics of? Crank, rod journals and rear main?

The factory rep is claiming that my stator messed up causing an electromagnetic field that caused the crank to run to one side and chew up the bearing surface. There is some damage to the magnets and stator which i believe occurred after the main failed and allowed the crank to walk to the side, therefore allowing the stator to meet the flywheel in an unfriendly manner. I'll have to file a disputed warranty which involves me shipping the engine to kohler on my dime and having them take a look at it in 1 to 3 weeks and letting me know whose fault it was.

My issue is this. If an electromagnet field was created, how would it retain enough polarity with flywheel spinning at 3650 rpms to cause oil failure to the front main? It's horse crap, they are trying to get out of the warranty. What happened to the front main was due to lack of oil - plain and simple - probably an obstructed oil galley. I am just mad i couldn't spend 2 hours of my work day standing in the shop watching them retrieve whatever was plugging the oil galley and reducing the oil flow. Then laying this electromagnet BS on me.

Restrorob
09-09-2010, 10:02 PM
What do we pics of? Crank, rod journals and rear main?


Yes, That would be helpful.....

I've got a few years on piston slapper, As he stated it's un-clear what failed causing this bearing failure. But, I've seen many many magnets come loose and get wrapped up in stators. I've never seen one wear a bearing on one side such as this. I just don't see how it could happen without loss of power (magnet to stator rubbing) and a lot of racket going on while running.

This electromagnet deal the rep is talking of may stem from issues Kohler was having with poor grounding PTO clutches, They would seek ground through the crankshaft and PTO bearing causing a bearing failure. I don't recall hearing anything about a issue such as this with the stator or flywheel end bearing.


Sounds like the guy that looked at it and his rep need to go back through Kohler's failure analysis course.

piston slapper
09-10-2010, 09:07 AM
Pics of the rod bearing surfaces....


remove the oil pump and look at the rotor and clover gear...Take a pic...
Pic of the cam lobes (metal in the oil after only 3 hrs) Kohler had some cam issues a few years back , the cam lobe would wear down and fill the oil with metal.
Pics of anything that doesnt look clean and new.

It sounds like alot of work , But , you might just get it warranteed .
Parts dont lie.....People do..