91' LE wont stay warm.

[allahsone]

i have a 91' corolla LE AT, with about 140,xxx miles.

before i go to work every morning a let it run for about 10 miutes. and on my way to work i notice that my tempurature gauge is slowly dropping. as soon as it hits right below the C my transmission seems to drop down a gear and i start high reving as i go down the highway. after high reving for a while the engine heats up a lil bit and the transmission shifts back into overdirve. and teh procces just repeats over and over again. i checked my fans out. and they do not constantly stay on. the come on and off normally. what could be done to fix this problem.

thanks.

[Flashmn]

Thermostat might be stuck open.

[94_Rolla_Guy]

if it never gets up to temp unless its sitting id tend to agree with flashmn, being the thermostat is stuck open,
the other thing it could be is that its just to cold and the by-pass holes in the termostat and the heater are keeping it cool, to help, get some cardboard or plasti-core and make a "cover" for the rad with some holes in it to let some air through, to reduce the efficency of the rad , this works for me, what i do for winter, then slip it infront of the rad with some string or something to secure it then if it runs hot make the holes bigger.

[allahsone]

the coldest it gets out here is like 40 degrees its not that cold

[REN69]

The transmission shifting up and down has nothing to do with the temperature, sounds like the OD switch is dead. My dad's Toyota van used to do that when the OD switch was dying. Eventually it only stayed in 3rd gear and we had to replace the switch.

[allahsone]

anyone have instructions or scematics on how to change thermostat. also does anyone know where can i download the service manual