I think he mentioned something about putting in a new thermostat when he put in the new water pump, replaced the timing belt and fixed my exhaust system.
He's got a heavy Spanish accent, so sometimes it's hard to understand what he says.
I still haven't been able to understand his three signs that it's a head gasket problem!
I'll mention putting in a new thermostat Monday. Thanks for all the advice!

 

He said he already put in the new thermostat. When he started working on the car, he saw a bunch of green on the radiator. He investigated further, and he said it was also leaking coolant from the radiator, and all the damage was coming from corrosion at the bottom of the radiator. He told me the radiator could go anytime, and because the damage is on the bottom of it, I'd lose all my coolant when it collapsed. He said he'd do both jobs for $325 cash, so I gave him the okay.
He showed me the old radiator when I picked the car up, and the damage was on both sides of the radiator, encompassing about five or six vertical lines, so I guess I did the right thing.

 

Sigh... that problem should have been noticed earlier in my opinion. If that is the fix, I'm glad to hear you are good to go now.

 

Yeah, I was thinking the same thing, but I think he put something in the coolant that he could trace leaks with. At least that's what I tell myself!
Thanks for the help!

 

Coolant itself exhibits leaks pretty well on its own... maybe find someone different to work on the car or do it yourself from now on? It ain't rocket science.