I have been getting the temperature overshoot problem that so many people seem to be getting with their Toyota pickups. My truck is a 94 4x4 with the 22re engine and the temperature gauge on start up sometimes goes all the way up to almost the red section of the gauge until it will finally go back down to just below the half way mark. This problem seems to be getting more common lately.My question is will changing the thermostat correct this problem and if so are most people going with an aftermarket or with a Toyota thermostat? Does anyone have the Toyota thermostat part# for my truck?

 

only use toyota oe parts and the number is 90916-03083 if it bugs you enough just get an aftermarket temp gauge

 

Thanks for the part #, I ordered a new thermostat and gasket from the dealer today and hopefully this will fix the problem.

 

To be honest, if the gage goes to red on first start up, then is sounds more like a sender problem. My tempature overshoot happened when running the truck for about ten minutes. The thermostat would not open because the outlet for the heater put semi cooled coolant before the thermostat making the thermostat not open when in reality the engine was hot. The dual stage thermostat has two valves and the smaller one would open at a lower tempature allowing coolant to move through.

Just don't be suprised if a new thermostat dosen't fix your problem. It could be you have a bad sender...

 

Yeah, if the wire is disconnected, or there is an "open" connection, the gauge will float right to the top. This can be caused by a bad sender, which has been mentioned or just a loose connection.

Random note: The oil pressure gauge will read zero when disconnected, and can be very worrying if it's loose

 

Sorry fellows but I wasn't very clear in my original post, but it happens when I first start the truck with the engine fully cooled, and as the engine warms up while I am driving the hand slowly increases to almost the red zone on the gauge, this usually takes 10 to 15 minutes. I talked to the parts guy today and told him the year and engine size for my truck and ordered a thermostat. He did not mention anything about a dual stage thermostat, so I hope it will solve my problem.

 

It could be the radiator cap als, I always change my cap and thermostat at the same time. How many miles do you have on the engine? It might be your waterpump

 

I have about 98000 miles on it right now. The temperature is fine after the engine warms up initially and the temperature remains steady at just below the 50% mark on the gauge. Wouldn't a water pump issue see higher running temperature at all times?

 

yeah, it sounds just like your thermostat is sticking.

 

I'm experiencing a similar temperature overshoot issue. On a cold start up my temperature gauge on my dash will slowly rise until it almost hits the red section (10-15 minutes) then will come back down to normal operating temperature. I have replaced the water pump (Not OEM), installed a 2-stage thermostat from 22re performance, installed a 3 row radiator from LCE preformance and am still experiencing this issue. My flan clutch seems to have appropriate resistance when cold as well as after being warmed up but I'm not positive.

Thinking about installing a new temperature gauge or an aftermarket mechanical temperature sensor but not positive this is the best move. It seems like my temperature sensor isn't faulty given that it slowly warms up and returns to normal range after that initial overshoot. Any advice?

Thank you.

 

Also when I drained my coolant from the engine block there was about half a handful of rust and metal bits as well as a orange tinge around my old thermostat. Seems like my old radiator had rotted away inside.

 

As others say, go for the likely things first:
1) Replace thermostat. Easy and the most likely issue.
2) Make sure you fan clutch is working and your radiator fan actually is spinning pulling air through the radiator.

After that you can get into the less likely things like plugged radiators and failed pumps.

 

I've found that when you first start a cold truck, you can hear the fan clutch engage. It give the engine a "breathy" sound. Almost like a moan. And it blows a lot of air. All this is when it first starts, cold. After a few seconds of blowing air like crazy over the engine, it fades out, including the "breathy" sound. To me, that tells me my fan clutch is working properly, and disengaging when it should. The air it blows tells me it's engaging properly.
It's been a pretty reliable check for me. If you want to be sure, you have to get it warmed up good, and listen for the breathy sound. When you hear it, you should be able to pop the hood and feel the extra air being blasted over the engine.

You can't look to see for clogged cores, since your view from the hole where the filler cap goes is pretty restricted. I've found, however, that when the thermostat first opens, and you get the hot water flowing into the top of the radiator, you can feel the outflow hose for the hot water. If it gets hot right after the inflow hose, the cores either aren't clogged, or aren't very clogged. If it takes a LONG time for the bottom hose to get hot, well, to me it says clogged cores.
Alternatively, you can drain the system, pull the bottom hose, and put a garden hose into the filler cap. If the water comes out nice and fast, the cores aren't clogged. If it has a restricted flow, IE not much water flowing through, well...
Otherwise, you have to take it to radiator shop, where they pull the tanks off, and rod, and comb, the cores. Really, it's probably cheaper and faster to just replace it at that point.

After finding that "ick" when you drained the system, flush it. Replace the radiator, thermostat, and three big hoses. At least. As long as you're doing, may as well check the hoses leading to/from the intake manifold and throttle body.
Then flush it well, and repeatedly, Until you don't get any "ick" coming out any longer.
When you fill it, use the red coolant from Toyota, and distilled water. A little more expensive, but worth it in the long run. Make sure you burp it well.

All this is just anecdotal, and my personal experience. I am far from a professional mechanic, or radiator guy.
Again, just my personal opinions. YMMV.
I wish you all the best!
Pat☺

 

As Pat said, flush it. Make sure you flush the heater core and crack the block drain too