Originally Posted by ColoradoToy91

Thermostat Problem

Question: “Why does my engine temp go all the way up to the red before it comes back down to the middle of the gauge after I start it up in the morning. It only does this when the engine is cold and once it warms up it seems to operate normally. Could it be as simple as a stuck thermostat?”

Answer: (From Roger Brown’s Web Site - http://4crawler.cruiserpages.com/4x4...tml#Thermostat)

“What happens on the 22R and 22RE engine, when the coolant goes through the heater core it gets cooled off enough that when it gets dumped back in on top of the t-stat it shuts it. Therefore the temperature in the engine continues to go up. The t-stat that I have mentioned has two valves in it, one at the regular temp. and one smaller on at a cooler temp. If the cool water shuts the big one, the smaller one stays open. All this happens because of the lack of a by-pass hose, which on other systems, keeps hot coolant running on the t-stat.”

You can get the two-stage thermostat mentioned above from your local Toyota Dealer.
Part Number: #90916-03070