Running without Thermostat - Cools better?

[kylestyleup]

I just did my regular check on my valve clearance and flushed my radiator/cooling system.

I drooped my thermostat and it fell down the drainage.
I need to go to a client and have no time to buy a replacement.
So I put everything back except for the thermostat.

It seems everything is OK and the temperature is a bit cooler than normal.

Can I run my engine without a thermostat at all?

[Gavatron]

Not a good idea.

Motor running cooler may make the ECU run more fuel. The thermostat also controls the speed of the flow through the radiator. If the coolant is flowing through too fast, it won't dissipate enough heat to the air.

[oldcorollas]

you can, but it will take a longer time to heat up, and may nto stay warm.

as well as the points above, the idea of thermostat is to slow the water to a trickle when cold, so the water in the block warms up faster.

the coolant needs to be a certain temp, so that the oil is at a good operating temperature.
if the oil temp is too low, it will be thicker, and will not make any water or fuel evaporate out of the oil.

thermostats are heap, so replace it when you can, but for a little while it will not be so much of a problem. ie, it shouldn't kill the engine in a few days...

[kylestyleup]

Not a good idea.

Motor running cooler may make the ECU run more fuel.

I'm running in carby.

Not a good idea.

The thermostat also controls the speed of the flow through the radiator. If the coolant is flowing through too fast, it won't dissipate enough heat to the air.

That's what I thought at first. But I got back safe.
I even tested it the next day...
after I run engine after 5 mins. with some aggressive gassing, I can touch the water and it's not that hot...

[kylestyleup]

you can, but it will take a longer time to heat up, and may nto stay warm.

as well as the points above, the idea of thermostat is to slow the water to a trickle when cold, so the water in the block warms up faster.

the coolant needs to be a certain temp, so that the oil is at a good operating temperature.
if the oil temp is too low, it will be thicker, and will not make any water or fuel evaporate out of the oil.

thermostats are heap, so replace it when you can, but for a little while it will not be so much of a problem. ie, it shouldn't kill the engine in a few days...

Maybe you're right.
I'm not good at auto parts... I wanted to buy a new one but I don't know the part number.
I always use the damaged ones as sample when I replace things.

The nearest auto supply can't give me a correct thermostat with out the part number.
Sales girl don't know if I just say "Thermostat for 18R".... duhhhh

[JoJo]

Your engine is designed to run at a certain operating temprature. This is for best running efficiency. Cold engine = more engine wear.

With no thermostat, it does'nt reach these temps, Sure it will run, and you could drive it daily with no problems, but your engine wont get as much life out of it over time....


J Riftin

[feral4mr2]

some cars seem to run ok with no thermastat (for a while anyways), while most others will run cold for a long while like mentioned above, then once warmed up end up overheating as the water/coolant is passing through the radiator too quick and doesnt get a chance to cool.

most auto shops will have a book in the isle the thermastats/rad caps etc. are, take a look for yourself, brand of car, model of car, year and engine code. it's prity easy to work out.

[allencr]

If the coolant is flowing through too fast, it won't dissipate enough heat to the air.

That is just an old wives tale/myth that refuses to die, only because there is a rare bit of truth to it, unknown by those passing it along, that it's a false assumption, and even then, it sounds so ridiculous to begin with, I don't know why it ever had a life at all. The faster flow would pickup less heat, thus there's less to dissipate - Done. The exception I've heard about where it actually is true & convinced those that it was the speed, would be tough to figure out, so I can't really blame those few about real cause. It is a pressure decrease causing the overheating, not system from hot air & water, but head/water pressure in the head An open thermo. will restrict flow, increasing pressure enough to stop those nasty but normal hot spots from bubbling & getting cooled even less during a hard run.

You've already proved by yourself that it'll run cooler and if you've got a thermo on the inlet side of the system, then even the exception will never happen with the restriction at that location.
Some of these Toyota's have huge bypass systems, so you wouldn't get the usual problems with running way too cool.

[FASTFOO]

That is just an old wives tale/myth that refuses to die, only because there is a rare bit of truth to it, unknown by those passing it along, that it's a false assumption, and even then, it sounds so ridiculous to begin with, I don't know why it ever had a life at all. The faster flow would pickup less heat, thus there's less to dissipate - Done. The exception I've heard about where it actually is true & convinced those that it was the speed, would be tough to figure out, so I can't really blame those few about real cause. It is a pressure decrease causing the overheating, not system from hot air & water, but head/water pressure in the head An open thermo. will restrict flow, increasing pressure enough to stop those nasty but normal hot spots from bubbling & getting cooled even less during a hard run.

You've already proved by yourself that it'll run cooler and if you've got a thermo on the inlet side of the system, then even the exception will never happen with the restriction at that location.
Some of these Toyota's have huge bypass systems, so you wouldn't get the usual problems with running way too cool.

except when it is a late model type thermostat that blocks the bypass when it opens. Like most Toyotas from about 1986 on.
When you remove one of them and it continues to bypass the radiator and it will overheat!! (maybe where the "water flowing to fast myth came from?)

With an 18R it should be fine and any parts person worth ther salt should know what you want if you ask for that.
MATT

[MWP]

If the coolant is flowing through too fast, it won't dissipate enough heat to the air.

That is just an old wives tale/myth that refuses to die...

Thankyou!!
I was just about to say the same thing...
So many people say this without ever really thinking about it.

[jimmmayyy]

Seriously, it won't matter a shit! A thermostat is only there to hold water in the block for cold starts. I don't have one in mine atm, and all our cars back home run no thermostats because it pretty much never gets cold there. It'll be fine, if you feel like putting one in for winter then its really no big deal.

[JoJo]

Seriously, it won't matter a shit! A thermostat is only there to hold water in the block for cold starts. I don't have one in mine atm, and all our cars back home run no thermostats because it pretty much never gets cold there. It'll be fine, if you feel like putting one in for winter then its really no big deal.

Not true, sorry......

As i stated, the water never reaches op temp so engine WEAR will happen, even though it may 'run' fine and the water may feel phically hot, but its not up to temp.

A simple test:

Run the engine for 20 mins WITH a thermostat - Use a thermometer or numbered gauge to get temp reading

then

Repeat the same test WITHOUT a thermostat.

I bet the second test will have a lower temp, therefore engine is not up to best temp efficiency.

With ae86 with a 4AGTE, When i ran that with no thermostat, the water temp wouldn't get higher than 42deg! Thus, making the microtech computer constantly running startup/cold mode all the time.

With the thermostat, it would happily run at the engine at its designed running temp, 87deg......

NOT RECOMENDED ON EFI CARS. YOUR COMPUTER WONT BE HAPPY

[Roscos]

If you are running an alloy head, yes you need a thermostat, if you are running a dirty old cleveland or chev it doesn't matter.


Roscos

[jimmmayyy]

Ahhh true cold start of course, I didn't consider that. None of my cars have ever done it, but I can see how it could be possible.

[Kyosho]

I've seen engines over heat from no thermo but the coolant was still "cool"...
Why, the water wasn't removing the heat from the metal!