Will a Car Run Hotter Without a Thermostat?

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

import silvia said:
Without a thermostat the system will run cooler as a whole. That is the way chemistry and physics work.
Click to expand...

I'm not sure the above statement can be verified scientifically. If the engine and all it associated hardware is running at say 180*F at 18psi, with no thermostat, the radiator will see a temperature difference from inside to outside of 100*F, assuming an ambient temperature of 80*F. If, however, a thermostat were installed, which would only allow water out of the water neck at 200*F, then the temperature difference across the radiator wall would be 120*F. Since the greater the temperature difference, the faster the energy dissipates, the "overall system" will run cooler because it is dissipating more BTU per unit of time. The temperature in one part of the system will be higher (the radiator), but the total energy dissipation is greater per unit of time.

Sure, in certain situations there will be observations that "this one time [at band camp];) I ran my car without a thermostat and the gauge on the dash read lower than usual." I'm not able to account for all the variables in that scenario. Ambient temperature, wind speed, vehicle speed, altitude, vehicle load, driving style, etc. I can, however, take all those variables out of the equation and speak about it from a purely physics perspective.

Regards, Luke
 
I was always under the assumption that the thermostat was a just a "smog" device. Smog meaning.... helped burn fuel more efficiently under start up conditions. It helped the engine warm up quicker by not circulating the cold fluid. The thermostat did not open until the fluid in the engine reached a certain temperature. Once operating temperature was reached the thermostat stayed open.

I get the argument on the system works on temperature differentials... but that argument is valid only when the system is running at operating temperature. Temperature differential has nothing in the game until the thermostat is open. Fluid picks up heat... radiator dissipates heat.... The thermostat just sits there and picks his nose while all this is happening.
 
I remember reading once that the Landcruiser thermostat serves some additional purpose in the housing and that if you pull it, more water recirculates through the block, and less through the radiator.... so you actually run hotter because you aren't restricting the block circulation.

I may be remembering wrong, that does happen, but I think that this time, maybe I got it right. Maybe.
 
dont really feel like breaking out the heat transfer book, but you have to realize that mass flow rates come in to play. assuming the mass flow rate of the air flowing over the radiator stays the same in both situations, and the efficiency of the radiator stays the same (didn't change that radiator in both situations), the only real thing we are changing by the thermostat removal/restriction is the mass flow rate of the coolant. and that mass flow rate has to be optimized for the eficiency of the radiator.

the increase in pressure of the system that comes as a result of using a higher pressure radiator cap allows the system to run at a higher temperature without boiling.... which is bad for obvious reasons... the thermostat doesnt affect the pressure of the system.

now if you put in some monster radiator that can handle the added flow, removing a thermostat may help.

anywho, hope this helps.

have fun with the convo.
 
Hopefully, car cooling systems were designed for the worst case senario so, under most driving circumstances, they have excess cooling capacity. On older style cooling systems (our TLC's), the thermostat acts only as a restrictor to the flow of coolant from the engine through the radiator, thereby effectively limiting the transfer of heat from the engine to the radiator and hence to air to an amount sufficient to keep the engine temperature in the optimum operating range.

As designers created smaller, lighter, higher horsepower engines, the circulation of coolant, in addition to transfering heat to the radiator, is used to equalize temperatures within the engine. In this type of cooling system, the thermostat, rather than just restricting the flow of the coolant to the radiator, REDIRECTS the flow of coolant through a bypass back through the engine, insuring a constant flow through the engine. If you remove the thermostat, the coolant is free to flow through the radiator or through the bypass. Since the bypass provides the path of least resistance, little or no coolant will flow through the radiator, and therfore engine temps will go up.

The "speed" at which the coolant flows through the radiator has no bearing whatsoever on its ability to transfer heat. Heat transfer is primarily governed by the properties of the coolant, the surface area, and the TEMPERATURE DIFFERENCE.
 
Unless you have a hot-water recycling loop in your home, the pipes under the house aren't a very good analogy for thinking about your radiator.


rover67 said:
think about the water pipes in your house....
Click to expand...
 
Me dumb dumb, but try answer anyway

  1. Thermo restrict flow till coolant reach operating temp, then open
  2. Thermo stay open long as coolant at least operating temp
  3. Thermo close when coolant below operating temp so system warm up
  4. Thermo stuck open cause hiney freeze off in cold weather!
  5. My hiney is ugly
  6. Engine that run hot with no thermo or stuck open thermo, run hot with new thermo - cause french come out of mouth and $$ come out of wallet to chase source of overheating
  7. Water moving fast over radiator with no thermo in system make more laps through system. Even though less heat removed on each pass through rad, higher rate of passes means same heat removed.
  8. More gooder to run with operating thermo;)
 
thank you for the summary















kemosabe'
 
i think it is a good one, the pipes act like a simple heat exchanger just like your radiator. thats all i'm saying.
 
Butt Ugly Chuck said:
Me dumb dumb, but try answer anyway

  1. Thermo restrict flow till coolant reach operating temp, then open
  2. Thermo stay open long as coolant at least operating temp
  3. Thermo close when coolant below operating temp so system warm up
  4. Thermo stuck open cause hiney freeze off in cold weather!
  5. My hiney is ugly
  6. Engine that run hot with no thermo or stuck open thermo, run hot with new thermo - cause french come out of mouth and $$ come out of wallet to chase source of overheating
    [*]Water moving fast over radiator with no thermo in system make more laps through system. Even though less heat removed on each pass through rad, higher rate of passes means same heat removed.
  7. More gooder to run with operating thermo;)
Click to expand...

does the water pump still spin the same rpm before and/or after the removal of the thermostat?

.
 
In my trips to baja where temps are commonly in the 100's and sweaters are unkown, the locals remove thermostats. Seems to work in a very very hot environment to keep the water flows going.

Not hotter...cooler.
 
what some of you guys are forgetting is that these engines have a normal operating range for temperature. Too cold or too hot...you have problems. Too cold the engine is not efficient and does not operate efficiently, the oil does not get to the correct temp...etc. Too hot obvioulsy you have overheating. The thermostat helps to maintain the operating temp in the winter and to assist in the warm-up process. In the summer.... a thermostat does not do much..but it still keeps the engine in the normal operating range for best efficiency.

I don't care what the temps are either extreme cold or hot....my vehciels will have a thermosat. I've been in the real deserts overseas and I know what hot is...

You are not going to gain any advantage on running without a thermostat. Other than frezzing your @ss off in the winter.

I've not met one mechanic that offers the advice to remove the thermostat. Granted ...in the summer its not a big deal.... in the winter its going to be bad news.

I gurantee you will accelerate engine wear in the winter without a thermostat.
 
Butt Ugly Chuck said:
The water pump is belt driven. RPM's directly relate to engine RPM regardless of thermo condition.
Click to expand...

In most cases, yes. But not always.

I'm running a variable speed, remote electric water pump on the small block in the 45. Plumbed with -8 AN lines, to an aluminum 19X31 two core, 1" tube Griffen radiator. The fan is variable speed electric, too.(and no thermostat, but that's a different story):doh:
 
I'm gonna go with Elbert on this one...t-stat is there for a reason. Removing it will not "fix" anything... only mask it.
 
45Kevin said:
Do boat motors have a thermostate or just constantly flowing lake or sea water?
Click to expand...

The one salt water boat I work on has a thermostat. Its got a Ford 302 in it, and it uses a heat exchanger system to cool the coolant. Most salt water vessels have this system because salt water running through and engine will shorten its life drastically.
The other, with a Buick v-6 odd fire is a lake boat, has the water cycle through the engine. No heat exchange system for the coolant, but I'm not sure about the thermostat, I want to say it doesn't have one. To go along with this, this engine is not run in air temps below 50-55 F, and the water is never below 45 either, so there isn't the issue with cold winter temps causing issues with the engine
 
Ok I have the Answer.

My Thermostat stuck open while out wheeling on Sunday, I have a new radiator too, Normal Temp is at about a 1/4 and never moves from there once warmed up. I now only just makes the cold mark, Gauge is fine as it the sender.


So without it runs colder.

Now I have to fix the thermostat :censor:
 
You must log in or register to reply here.

Share this page

Back
Top Bottom