jreask
Member
Oh boy, that was brilliant.
Overheating, Help!
- Thread starter Park
- Start date
Oh boy, that was brilliant.
brian2sun
Elite Member
I've never heard of an engine overheating from a thermo stuck open. But if it's stuck closed, then it can definitely overheat because the water will stay in the engine and keep getting hotter and hotter.
A thermo that's stuck open will run fine on a hot day because once the thermo opens up after a couple minutes after start up, it's going to stay open normally until the engine is turned off. But on a cold day, a stuck open thermo will take a long time to get up to normal operating temp.. and if it's really cold, it could cause low idle and even stalling.
A thermo that's stuck open will run fine on a hot day because once the thermo opens up after a couple minutes after start up, it's going to stay open normally until the engine is turned off. But on a cold day, a stuck open thermo will take a long time to get up to normal operating temp.. and if it's really cold, it could cause low idle and even stalling.
tx4r3g
New member
a stuck open tstat will over heat on a pretty hot day.and on real cold days it wont let the motor heat up which means no heater inside the cab. and a tstat doesn't just stay open at normal temp. they are designed to open and close at a certin temp they heat up to a certin temp and open to let the hot water from the motor go to the radiator and let the cooler water from the radiator go to the motor. when the cooler water hit the tstat it will close and then it just repeats the process over again. so I guess from what you all are saying I can just take my tstat out and not run one at all. and all would be good......NOT LIKELY..I think we hijacked this thread enough. Does anybody know if parks found his problem? I think it was a hbead gasket.....
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Robb235
Senior Member
Taking out the t-stat, and the engine running hotter is one of those myths that's been around since forever, probably 5 minutes after the first liquid to air radiator was installed into the automobile. The idea that the coolant flows so fast that it doesn't pickup heat in the block, and can't dump it's heat at the radiator is nonsense. This is like saying if you turn on the hot water faucet in your kitchen at the highest flow rate possible, that it would heat up the metal faucet slower than if you had a slower flow rate of water coming out.
Basically for a given amount of coolant, the slower rate of flow will remove more heat (up to a point), BUT, the higher flow makes up for this by cooling a greater mass of coolant. The greater flow of mass makes up for less time in the radiator and you end up removing the same number of BTUs from the engine.
Robb235
Senior Member
Also, I do have some "field experience" with this.
When I was in college, I had a Monte Carlo that at one point had the t-stat stuck closed. I took the t-stat out and ran it for quite a while. I can't remember if I ever put a t-stat back in before I eventually sold that car to a metal salvage facility. Point is, with no t-stat, I never had an issue with it running hot, whether on the freeway or in the city. It always took forever to warm up, and in the city it would occasionally get up to operating temp. On the freeway it would only run 1/3 of the way up the temp gauge (1/2 was operating temp).
There's also my motorcycle. It has a 160 degree t-stat, however it rarely ever runs at that temp. It's almost always hotter according to the digital readout in the gauge cluster. That means once warmed up, the t-stat is always open, especially in the summer. By your logic, my bike should be overheating like hell running the t-stat open like that the whole time, but yet it doesn't.
When I was in college, I had a Monte Carlo that at one point had the t-stat stuck closed. I took the t-stat out and ran it for quite a while. I can't remember if I ever put a t-stat back in before I eventually sold that car to a metal salvage facility. Point is, with no t-stat, I never had an issue with it running hot, whether on the freeway or in the city. It always took forever to warm up, and in the city it would occasionally get up to operating temp. On the freeway it would only run 1/3 of the way up the temp gauge (1/2 was operating temp).
There's also my motorcycle. It has a 160 degree t-stat, however it rarely ever runs at that temp. It's almost always hotter according to the digital readout in the gauge cluster. That means once warmed up, the t-stat is always open, especially in the summer. By your logic, my bike should be overheating like hell running the t-stat open like that the whole time, but yet it doesn't.
tx4r3g
New member
so why have a thermostat? its not a myth I have seen many cars and trucks over heating due to stuck open or no tstat. if what you are saying is true why do professioal race teams. run them. all my 1/4 mile drag cars had to run tstat if not they would over.if ididnt run one at all at higher rpm 7200 the coolant would cavatate in the radiator from moving ti fast.
tx4r3g
New member
brian2sun
Elite Member
The thermo is still needed so your engine can get up to operating temp in a reasonable amount of time after a cold start (and also run at the normal operating temp - as opposed to running cooler with no thermostat). I agree that on a "normal" day, a thermo will open and close several times on a long drive. But on a particularly hot day, it's going to stay open for much longer periods of time and may never close at all during the drive.
As far as how this relates to the OP, IF his overheating problem has anything to do with the thermo, I would bet money that it's stuck closed, not open.
Robb235
Senior Member
Why have a t-stat? Because you don't always need the maximum cooling capacity of you're cooling system all the time. The t-stat keeps the coolant at a constant temp as opposed to the big fluctuations that I had in the Monte Carlo going from light to light (around 1/2 on the gauge sitting at the light, to 1/4 when I began moving again). The car ran cooler than it should (not hotter) and I know this hurt my MPGs, and probably emmisions as well.
I'm not advocating that everyone take out there t-stats. It's there to help regulate engine temp. However this notion that the OP taking his out will cause overheating is just silly. The opposite will happen.
tx4r3g
New member
nobody told him to take it out it was just suggested that it might be stuck open and to ck it. then the comments started 1: this don't sound right.2: because its not 3: nope.... great comments by the way.. by the way like I said before done hijacking this thread. been great conversating about all this. enjoyed it..hope I didn't make anyone mad..
BlackCat914
New member
Ok thanks!
BrianSD_42
New member
It is not "hijacking his thread" when the information is related to the OPs problem.
There is nothing wrong with people disagreeing or saying you are wrong. If you say something expect to be questioned and able to back it up - that is just how things are here.
I said it doesn't sound right because it didn't to me. The fact that 4+ people are letting you know .... Well at least consider they might be right. You can always start a new "ultimate debate thread: thermostat edition" thread. We love those.
Obviously you are just trying to help but so is everyone else.
There is nothing wrong with people disagreeing or saying you are wrong. If you say something expect to be questioned and able to back it up - that is just how things are here.
I said it doesn't sound right because it didn't to me. The fact that 4+ people are letting you know .... Well at least consider they might be right. You can always start a new "ultimate debate thread: thermostat edition" thread. We love those.
Obviously you are just trying to help but so is everyone else.
Robb235
Senior Member
Mine doesn't run hotter. Mine stays right at 189 degrees according to my scanner.
As a former ASE Master Tech, and having built numerous engines over the years, mostly racing engines, you are wrong to say an engine can't overheat without a T-stat.
Under the worst conditions, usually hot ambient temps, and high load on the engine, a cooling system without a thermostat can do exactly what "Tx4r3g" said.
A 3rd gen 4Runner has a fairly large cooling system capacity, as it is a truck that is designed with the ability to tow a fair amount of weight. So under most moderate ambient temps and light loads, it can run without overheating, if the T-stat is removed.
Under more demanding conditions, and without a T-stat, the coolant can be flowing fast enough that it's not able to absorb the increased BTU output from the engine sufficiently, and since it is flowing quickly through the system with no regulation from a T-stat, it isn't in the radiator long enough to shed the BTU's.
Now when ambient temps are cold to moderate, and no T-stat is present, the system can take a long time to reach operating temp, because the cold air blowing through the radiator fins is enough to cool the fast flowing coolant.
Even when a T-stat is wide open, it still restricts the flow of coolant enough that the coolant is present in the engine long enough to pick up the heat produced by the engine, and then shed that heat as it flows through the radiator.
Cooling systems are carefully designed to work within the limitations of the vehicle. Once that system is altered, without a full understanding of the consequences of those alterations, the performance of the cooling system can fail at the worst possible time. Ie: Little to no heat in extreme winter temps, or overheating when pushed hard in hot summer temps.
So the bottom line is that a cooling system without a T-stat can run cold at cold to moderate temps and loads, but can also overheat at higher ambient temps and loads.
If you don't want believe me read this article, and pay particular attention to the section regarding the Thermostat: Automotive Cooling Systems -* A Short Course on How They Work | CarParts.com
