Mark
I had a leak in the fitting betwen the flush tee added into the hose tonthe heater core.
I decided that while i was replacing that hose i should also replace the othe coolant system hoses.
Then i found the thermostat was wedged open with a nut so i've replaced the thermostat.
Half way through burping the system but so far so good.
Geoff, I did not notice the nut until you pointed it out, however the inside looks good and no major signs of corrosion. At least the PO changed the coolant and did not let the system corrode. That "old" thermostat is a SAVARA brand and should have 80 deg. celcius stamped on the opposite end. These are the OEM stats in terms of manufacturer and temperature range. Newer thermostats are usually about 90 deg. If you remove the nut and test the thermostat in a pot of boiling water does it open fully, and when cold is it fully closed. If so, don't throw it away, keep it.
I wonder if it truly was a PO modification or the nut somehow got into the cooling system and lodged itself in there.
that's what I said somebody probably told the po to just remove them so there is no issue LOL replaced with new one from Autoricambi and have never looked back