My 89 project was having an overheating problem so I removed the thermostat to trouble shoot. The thermostat opened slowly around 190f when I boiled it, but just for giggles I ran the engine without it to see if I could get it to overheat again. And I couldn't. I let it idle in my driveway for awhile (p.s. its over 100 degrees outside here) nothing. drove it around my neighborhood, still nothing. never got over 1/2 on the gauge.
Im going to pick up a new t-stat anyways but I'm curious, what happens when it runs w/o it? I've read everything from "nothing" to "your heater wont work" and "your engine will over heat".
My heater works fine, no overheating either. Anyone have any toyota specific experience with this???
Note: I'm running the 5vz if that makes any difference.
-Thanks

 

The main concern is getting the engine to the proper operating temp for efficiency and emissions purposes. Without t-stat it may not get fully warmed up in cooler temps so your mileage may suffer a little. I notice you're in AZ, so depending on where in AZ, it could be 190* ambient....

And if you don't have emissions, then that's one less thing to consider....

 

You can but the heater may not work very well

 

-Increased internal engine wear due to excessive cold operation.

-Poor fuel economy.

-Poor Emissions control.(Check Engine MIL may illuminate).

-Poor Engine performance.

-Poor Heater/climate control performance.

Other than that your good.

 

I read the op and was like

What he said...

 

water circulating at full unrestricted speed(no thermostat) through the engine will not sink heat from the metal as well, which is why it looks like it's not overheating.

an open thermostat slows down the water flow, which gives the water time to absorb the heat.

no thermostat means that the engine is hotter, but the coolant is colder, so the ecu is adjusting the fuel and timing based on a colder engine.

 

When I bought a rebuilt 22r from a long standing and reputable Toyota rebuilder he gives a 3 year warranty and the only requirement he places is that you use a OEM Toyota thermostat. I'm guessing he knows something.

 

Somewhere (4Crawler's site?) there was a mention of Toyota fail-safe/dual control thermostat used because:
When heater is suddenly switched on while truck is already in operating temp, when coolant returning from heater core (cooler than temp at which thermostat opens) hits T-Stat, T-stat thinks coolant is still cold so it shuts off cutting off circulation of the rest of the coolant that's actually already in operating condition (190°?)

My truck's head gasket ( I hope not the head itself) is shut so considering to get that dual-T-Stat after HG is replaced.

 

that makes sense, good to know.
thanks!

 

yea what everyone is saying is pretty much right. a/c isn't gonna work right, the fuel injection isn't going to be optimized along with a whole slough of other stuff. just replace it. it not to expensive.

 

Yeah like I said, I had no intent of driving around without it, it's too easy to replace (and I'm sure the engineers at Toyota knew what they were doing when they put one in). Just wanted a better understanding of what it did because it seemed like there was a lot of misinformation floating around online.

 

Some of the guys at the racetrack do this, running the car flat-out most of the time keeps it at operating temps. But if you're on the highway part-throttle, the engine won't be happy staying too cold.

Rich

 

I agree with what everyone else is saying, with the cost of a thermostat being so cheap, why would you risk it?