Yikes—that doesn’t sound good, but you’re on the right track with your observations. The loud clanking, followed by the engine barely turning and the fan barely moving, could point to something serious like a seized engine or internal failure (like a broken rod or damaged crank). The hot negative battery cable definitely suggests there’s a major draw or mechanical bind—possibly the starter is trying to turn a seized motor.
A few things you might check before assuming the worst:
Try rotating the engine by hand using the crank pulley (with a socket and breaker bar). If it won’t budge or locks up partway, that’s a strong sign of internal failure.
- Pull the starter and inspect it. A jammed or broken starter gear can cause clanking and prevent crank movement.
- Check oil level and look for metal shavings on the dipstick or in the oil filter—could confirm internal damage.
- Inspect the flywheel/starter ring gear—it could have broken teeth if the starter’s been slamming into it.
It’s great you’ve already done a lot of solid work on the machine—it’s worth digging into a bit more before calling the engine toast.
As for videos, you might look up Kubota L35 engine teardown or D1703 engine rebuild (that’s the common engine in the L35). There are a few good YouTube walk-throughs from DIYers that go through step-by-step inspections and teardowns.
