I just finished replacing my timing belt, what a PITA. Anyway, I go to refill the system with antifreeze and low and behold the thermostat never opens to let me add more. I'm still sitting with half a bucket full of what I collected upon removal. I finally decided I must have installed the thermostat upside down. In the Haynes book it says to install with the jiggle valve 15* within the 12 o'clock position, now these directions were so precise I never questioned them, but I do remember the jiggle valve being on the bottom when I pulled it out. Just checked some of the stuff I downloaded from techinfo.toyota.com and found that they say to install it with the jiggle vavlve downward. Would this cause the tstat not to open or does it not really matter. I find it hard to believe the Haynes manual could have messed something up so badly that is extremely important to the engine.