Diagnosing Damage From Operation During Overheating

[Pgorman]

Let Friend use HST and he used for unknown period of time while engine severely overheating. He overfilled coolant reservoir to “fix it” and when I got there smoke/sream was pluming from engine and coolant was at a rolling boil.
I cleaned the screen, radiator, and emptied excess coolant. The engine seems functional, fan working, PTO working, but engine overheating after 15 minutes.

Besides the thermostat what issues should I be looking for?

Of course the friend can not afford to fix anything. I broke a basic rule: Don’t loan things to people who can’t afford to replace what they brake if you want to remain friends.

 

[#40Fan]

Head gasket at the least. Cost could go up a lot from there.

Remove the radiator cap and start the engine. Does it start bubbling immediately?

 

[North Idaho Wolfman]

Cracked head, pull the head to find out.

 

[old and tired]

Also, how well did you "clean" the radiator? Did you blow it out backwards (from the engine side) with compressed air? It takes a lot of time and effort to blow it out completely depending on how clogged it got.

For the record, I got to the boiling point with mine.... let it cool and clean the snot out of it. Been working fine ever since. I learned to watch the temperature gauge like a hawk now!!!