D15 cracked block, seized, how does it look?

It was pleasing to see that a forum like this exists.  I really appreciate it.

I think I seized it a few weeks ago.  Right now, I'm chalking it up as overheated seized and cracked due to lack of coolant, but with a 20% chance of something else.

The first start of the year, I let it idle for 2-5 minutes until I heard a weird sound and before I could get back to it to shut it down the RPM had gone lower and lower until it stopped, over about 5 seconds.  I forgot to check the coolant and it was down a half of a jug.

Edited by fartwhif - 18 Jun 2023 at 7:33pm

Sounds like it spun a bearing. Could be a rod or crankshaft bearing. If you decide it is more than you want to tackle. I would be interested in tractor. I live in Gallatin, TN Thanks, Tracy

I ran a B motor low on coolant ( about a gallon) and it "slowed down and locked up" as you said... The liners got hot and the rings  "STUCK" and froze the motor...... Since you said you put penetrant into the bores and it ran past the rings into the crankcase, you COULD have the same problem i had.. 

Before you get into the oil pan, do yourself a favor and remove the engine and put it on a stand. It may be a little more work right now, but it's a heck of a lot easier to be able to turn the engine upside down to work on it.

A ton of thanks for all the experienced guessing and tips.  I've taken off the journal bearings.  All the pistons are free.  Please correct me if I'm wrong, but I'm 70% confident it's spun main bearing(s).  I don't have the resources to do an out-of-frame rebuild so I'm hoping that I can use the cotter pin trick to replace those bearings.  I don't have the funds for crankshaft grinding.  If I replace the main bearings without getting the crank shaft ground first then what is the chance it would just spin again?  I would measure the crank and get the thicker bearings if needed (is that even possible?), would it be in danger of spinning even if graduating the bearing thickness because the crank isn't ground?  An unground crank and new bearings, what often happens? Unground leaves it in between sizes and perhaps also having weird shapes?  How important is grinding? Is it absolutely required?  Will they definitely spin again or have some other failure without?

Edited by fartwhif - 04 Jul 2023 at 12:59pm

Most often, a spun main bearing will damage the block and require line boring.

You can't really measure the main journals with the crank in the block. The half baked way you are talking a bout fixing is going to bite you in the a$$ and make it even more expensive to fix right. You have "precision" bearings and things have to be precise to work long term. If a shell slipped in the main bore it removed metal requiring line boring.