On the drive down to Tillamook last weekend I started to have over heating problems. I have had this problem ever since I put the motor in. Did some research and found that the main problem is the factory location of the thermostat. For some dumb reason Toyota thought it would be a good idea to put it on the lower radiator neck where all the cold water is coming into the motor, instead of up on the upper radiator hose neck where every other motor known to man has put it. So what happens with this design is the motor get warm while driving but the hottest part of the motor (the cylinder head) is getting near over heating. So the thermostat opens and let's a small gulp of cool water into the motor (the cool part of it) then because the thermostat is now swimming in cool water it contracts the spring and closes. This is torture on these otherwise great motors. Forcing them to constantly go through rapid changes in temperature. I have read of guys pulling over with a temp gauge in the red but finding a stone cold lower hose. No wonder they have head cracking issues. I know that mine had been replaced once already before I got it. To ensure that this problem gets fixed I have also ordered a new aluminum 3 core radiator. And will also check the oil in my viscous fan clutch.