The above is spot on! Good info.The most common cause is freezing coolant. This usually cracks the outside where it is visible but it can also crack inside. Just follow the trail of coolant. Internally engines can develop stress or heat cracks as well. They are normally found in the head.
Cracks in the head can lead to loss of compression and water in the cylinder, too much pressure in the rad. They could make it run rough and smoke, especially on start-up, so could a bad head gasket.You are looking for white smoke. That's coolant. If the smoke has a bluish tint to it, that's oil smoke. It's also possible that the valves are carboned up and not working properly.
You don't mention if your dealing with an air or liquid cooled engine but, as mentioned, heat will do it to either. Excessive vibration from out of balance attachments can cause cracks around manifolds, motor mounts and other attachment points. Adding excessive amounts of weight to exhaust ports and improper torquing of bolts can also cause problems.Ive read a few threads about cracked blocks, what causes it and how do you tell if a block is cracked? Does the tractor run rough and smoke?
It can drive though if it does have a cracked block though can't it..cause my buddy thinks he may be dealin with one himself and I told him to look at this conversation as it might help him figure it out but he said his is till running.The above is spot on! Good info.
To add alittle more info to the above. The freezing coolant is more than likely straight water or very diluted water/antifreeze mixture.
In this case there will be rust and corrosion in the block, head, radiator, hoses etc. There may be more problems than just a cracked block in this case.
Even tho most engines have freezeout plugs, they can get rusted in and not give.
Generally a cracked block will tell on itself as it won't be running right, if at all.
Another source of cracked blocks in old tractors where the engine constitutes part of the framing is from overloading FEL's. That stress has to go somewhere and generally it's the block.
Driveing these old machines as if they're ATV's can do it too.