Atomic / Universal 5411 overheating -SOLVED (by accident)

[Sail365]

Hi,
Just in case this helps anyone else
I have a universal 5411 that was heating up to 200 or so degrees. I couldn't figure out why. Every once in a while it would all of a sudden cool down and start bouncing between 120 and 160 like it used to, which seemed OK. I replaced the thermostat, the behavior persisted. I ended up draining the block (and blew it out w/ compressed air) for winterizing including cracking the impeller casing to get all the water out of there. When I started it up again, I ran it for a few seconds w/ the impeller still cracked, then sealed it up. Now, it's cooling perfectly. Basically sits at 145 w/o the previous bouncing around under load. My GUESS is that there was an airlock in the system. Or maybe there was an obstruction that draining the block by disconnecting hoses and blowing compressed air removed. But, maybe this will be helpful for someone. I searched and searched and was going down rabbit holes like blocking the return line, etc.., but never had to do that.