Weird One... Seized Kohler 7000 KT730-3046

[JonnyBlaze]

So I bought this 2023 Cub XT1 LT46 with .25 of an hour on it used from an older guy who said he was mowing and all of a sudden the engine came to a stop he opened the hood and saw oil all over the place. Said he had forgot to put the dipstick tube in all the way and it was coming out from there and it ended up seizing the motor. So he put it on craigslist, I made the trip and bought it. Got it home, engine was still full of oil and definitely locked up.

I started by checking obvious stuff, pulled plugs, still seized, pulled rockers, still seized, pulled flywheel, still seized, pulled heads, still seized, removed motor, pulled case apart, removed camshaft, unbolted connecting rods, removed them with pistons, inspected all the bearing surfaces and everything looked good.

Only thing I noticed was, I couldn't get the crank to come out of the block, like its stuck in the seal. It rotates like it should though...

So out of curiosity I put everything back in the case and put the two halves back together to see if it was still seized, and everything rotates like it should.... pistons go in and out, no problem.

So what gives? I don't want to put it fully back together and have it seize up again.

Any ideas? Machine literally has less than 30 minutes on it. Tia.

 

[Bertrrr]

I ran into something similar with a Honda machine, if it stops in exactly BDC the rod didn't want to break over - after forcing it to move off that spot- it's all good. Sounds like the same issue

 

[VegetiveSteam]

I'm guessing here but it's a guess from experience. The engine more than likely seized at that flywheel side bearing and some galling there is keeping the crankshaft from coming out. If that's the case the block is toast and there is no fixing that. I had some guys that were able to take a small sledge hammer and get the crank out and other times hitting the crank with a hammer would just break the top of the block. Either way the engines were not fixable. I have not seen this issue since the 7000 series was new and was more than likely not caused by the original owner not installing the dipstick all the way.

 

[JonnyBlaze]

I'm guessing here but it's a guess from experience. The engine more than likely seized at that flywheel side bearing and some galling there is keeping the crankshaft from coming out. If that's the case the block is toast and there is no fixing that. I had some guys that were able to take a small sledge hammer and get the crank out and other times hitting the crank with a hammer would just break the top of the block. Either way the engines were not fixable. I have not seen this issue since the 7000 series was new and was more than likely not caused by the original owner not installing the dipstick all the way.

So I shouldn't run it?

 

[VegetiveSteam]

So I shouldn't run it?

At this point I don't believe you can hurt anything by running it but if that upper bearing is indeed galled it will most likely seize again. But who knows? It might run fine for a long time.

I have also seen some 7000 series engines wear the upper main to the point of the hole being oval and then the crankshaft is running at an angle damaging the flywheel, the charging stator and the ignition module so if you do run it you might risk ruining those components at some point in the future.

It's been a while since I've dealt with a 7000 with a seized upper main bearing and I wasn't sure I was remembering the issue correctly so I made a phone call to refresh my memory.

There were a few of things that were causing seized upper main bearings on the 7000 series engines.

On the very early engines, Kohler accidentally installed Command series crankshafts in them and the top oiling hole on the Command crankshaft is different than on the 7000 series and that was causing the upper main bearing to not get proper lube and seize.

There was also an issue with the alignment between the upper and lower main bearings being slightly off which was causing upper main bearing failures. A little too much tension on the drive or deck belts was also amplifying this alignment issue on some brands of equipment.

Typically on a full pressure lubed engine the first thing to happen in a low or no oil situation is one of the connecting rods will seize to the crankshaft which is why I stated that the dipstick not being in all the way probably didn't cause the failure on this engine even though it was undoubtedly low on oil. The more I thought about that I started to remember that there was something about the lubrication path on the 7000 series engine that made me doubt myself and that's when I made a phone call to someone who knows and I stand somewhat corrected. The upper main bearing on the 7000 series is the last to get pressurized oil in that system so theoretically it could be the first to go due to a lack of proper lube situation. With a proper aligned crankshaft and no excessive tension on the belts the a typical failure due to a lack of proper lube could still be a connecting rod seizure.

 

[JonnyBlaze]

At this point I don't believe you can hurt anything by running it but if that upper bearing is indeed galled it will most likely seize again. But who knows? It might run fine for a long time.

I have also seen some 7000 series engines wear the upper main to the point of the hole being oval and then the crankshaft is running at an angle damaging the flywheel, the charging stator and the ignition module so if you do run it you might risk ruining those components at some point in the future.

It's been a while since I've dealt with a 7000 with a seized upper main bearing and I wasn't sure I was remembering the issue correctly so I made a phone call to refresh my memory.

There were a few of things that were causing seized upper main bearings on the 7000 series engines.

On the very early engines, Kohler accidentally installed Command series crankshafts in them and the top oiling hole on the Command crankshaft is different than on the 7000 series and that was causing the upper main bearing to not get proper lube and seize.

There was also an issue with the alignment between the upper and lower main bearings being slightly off which was causing upper main bearing failures. A little too much tension on the drive or deck belts was also amplifying this alignment issue on some brands of equipment.

Typically on a full pressure lubed engine the first thing to happen in a low or no oil situation is one of the connecting rods will seize to the crankshaft which is why I stated that the dipstick not being in all the way probably didn't cause the failure on this engine even though it was undoubtedly low on oil. The more I thought about that I started to remember that there was something about the lubrication path on the 7000 series engine that made me doubt myself and that's when I made a phone call to someone who knows and I stand somewhat corrected. The upper main bearing on the 7000 series is the last to get pressurized oil in that system so theoretically it could be the first to go due to a lack of proper lube situation. With a proper aligned crankshaft and no excessive tension on the belts the a typical failure due to a lack of proper lube could still be a connecting rod seizure.

Thanks for the info, I did notice this brown staining around the crankshaft seal. So that's probably a sign it got hot...