I replaced water pump and thermostat, fan clutch last Christmas 2011, when I did I put a low temp thermo in there. over the last week truck will get to the line before the break to red and stay there. Not every time I drive just sometimes. Its only done this twice in the last 2 weeks but thinkin I need to replace it. What do you guys think?

 

Pull t-stat and test it suspended in a pan of water with a thermometer to determine if it is opening properly. I'll test a new one this way to be sure it is good before dropping it in.

Radiator fins clean? Coolant full and in good shape?

 

You need to also consider that the coolant temperature sending unit might be bad as well.

 

If you didn't put in a factory toyota thermostat, that would explain it as well. As far as i know, ONLY the OEM thermostat will work well with the 22r/re. On mine i put an aftermarket thermostat in, and it would heat up to the red, then down, then heat up to red, back down, etc until it stayed in the middle. The factory thermostat is actually TWO thermostats in one, and although it's a bit more expensive than one from a parts house, it's worth it.

 

Not true. I have ran aftermarket parts store thermostats for the past 5 years and haven't had an issue at all. Factory is almost always a much better choice, but for me, the over the counter thermostats work just fine.

 

Yeah, it seems really hit or miss with parts store thermostats on 22rs. This is a pretty common problem, especially with the heater on.

http://www.4crawler.com/4x4/CheapTri...tml#Thermostat

 

yeahh...91 toyota pickup first time driving it in the winter time and it has been acting weird...when it starts to get hot i just crank the heat up on high and within a minute or two it cools off, not quite sure what to make of it.

 

I have had the temp guage to jump up even when it has been sitting for a long time. Here is how I fixed mine in the pic below. I also suggest cleaning your Cold Start Injector Timing Switch and Water Thermo Switch while at it.

Copied...
Here is a picture of a dirty Temperture Sensor. I have seen worse. I chipped some of the scale build up off so you could see a difference.


The sensor sits just below the Cold Start Injector in the Intake manifold. Uses a 17mm deepwell socket and is a 5 minute job.

 

Well pulled the thermostat, replaced it, then bout some system flush while I was there getting the coolant for it. ran that, and between the two seemed to help, I will be replacing the thermostat to the factory dual one as soon as i find someone going into salt lake city to buy one. Besides the o ring do you have to use any rtv?