We bought my son a 95 4-runner as a first car. It looked and ran like a very sound vehicle. 2 months after we bought the car (from a private party) it began to overheat. It progressively go worse. There was no leak or tell tale signs. My first thought was faulty thermostat. I purchased a new thermostat and when I removed the housing to remove the old thermostat, taaa-daaa! There was no thermostat in the vehicle. Is there a reason soemone would remove a thermostat and not replace it? I hope this is not a sign of things to come. Also, the water outlet (the coupling on the end of the hose that attaches and covers the thermostat) had a crack in it that had been sealed with gasket material. I now must replace that also.
There was obviously an over heating problem when the last owner had it, removing the thermostat is not a answer for this, it may be as simple as a part blocked radiator, get it out and core cleaned first, back flushing will not be enough it should have a full core clean done first, hopefully this is all that it needs, fit a new thermostat housing as well flush the cooling system and the heater, start here.