thermostat & a/t tranny problems

I just replaced the thermostat with one that I bought at the dealership in my 88 4runner 3.0 a/t tranny to solve the o/d & lockup converter problem. This thermostat doesn't let the engine warm up as much as the old aftermarket one did and I am not getting as much heat through the vents. I won't go into overdrive at all now..it would before if I was putting around town but would cool down in the highway and kick it back into drive...now it won't even come close. Is there a certain way that I should burp the cooling system and would an air pocket cause it to run cooler than it should. The temp guage only comes up about 1/3 of the way now...was riding almost at the halfway mark before. If anyone has any suggestions they would be greatly appreciated...thanx

It's possible that it's a faulty thermostat. See what the thermostat is labeled to open at. Take it out and test it by hanging it in hot water to see at what temperature it opens. See if it corresponds to the number on the thermostat.

I believe the temperature gauge needle is supposed to run at the 1/2 way point on the gauge.

Also, make sure you installed it correctly. I believe there are two ways to install them, only one is correct.

I called the dealer today and they said that they would exchange the t-stat, so I'm gonna try that...hope it works...thanks for the reply Brian. By the way, do you know if there is a way to make sure there is no air in the coolant system?

Fill the radiator when cold and idle the engine with the radiator cap off. When the thermostat opens, the level will suddenly drop. Keep the radiator full of coolant until the engine is at operating temperature (cooling fan has turned on at least twice) and then close the radiator cap - fill the coolant reservoir to the full hot line. The coolant circulation will push all the air in the engine into the radiator.

Fill the radiator when cold and idle the engine with the radiator cap off. When the thermostat opens, the level will suddenly drop. Keep the radiator full of coolant until the engine is at operating temperature (cooling fan has turned on at least twice) and then close the radiator cap - fill the coolant reservoir to the full hot line. The coolant circulation will push all the air in the engine into the radiator.

will do...thanks again brian!