Not really. Thermostats open and CLOSE.

For example lets say that you’re driving your car in the winter and the ambient air temperature is 20 degrees. So you’re driving along and your coolant temp reaches 178 degrees and your 178 degree thermostat begins to open. If it stayed wide open as you were cruising down the highway your coolant temperature would quickly plummet to around 140 degrees or so. You would have no heat and you would be cold and irritated. Instead the thermostat regulates the coolant flow to keep the coolant temperature in the indicated range.

The thermostat does play a role in the operating temperature of the engine.

 

That is completely wrong. I usually stay out of these threads because it gets really tiresome of arguing with people that dont have a clue about how the cooling system works.

I wrote this "book" in another thread, below, a while back and will copy paste from it so I dont have to type it all over again.

http://forums.corvetteforum.com/show..._id=101&arch=1

""""This is NOT how the cooling system or thermostat operates. I read a lot of posts about thermostats and there is a lot of misinformation about how the thermostat actually works and why engine temps are never what the temperature rating of the thermostat is.

This is going to be a little bit of a book, but that's what it takes to describe this operation.

The thermostat is the brain of the cooling system. Just like the computer is the brain of the engine. The thermostat is designed to regulate the flow of water in order to maintain a desired temperature depending on the temperature rating of the thermostat. When the engine is cold, the thermostat is closed and prevents the flow of coolant out of the engine in order to warm the engine up quicker. Once the engine coolant reaches the operating temperature of the thermostat, it starts to open to permit the flow of coolant through the engine and radiator. Air moves through the radiator and absorbs the heat which in turn cools the coolant. The cooler coolant now starts to leave the radiator and go back into the engine. If the coolant is colder than what the thermostat is rated for, then the thermostat moves toward the closed position in order to restrict the flow until the coolant warms up. If the engine is under load, high power, etc, then obviously it will be putting out more heat. The thermostat now opens more to increase the flow of coolant in order to cool the engine. The thermostat will continue to regulate the flow of coolant by slowly moving towards the open or closed position in order to maintain the rated temperature of the thermostat. As situations changes, primarily the outside temp, speed, and engine load, the thermostat will continue to regulate the flow of coolant accordingly in order to maintain its rated temperature.

For the below example, lets use the stock thermostat which will be 194 degrees.

Say, for example, if the outside temp suddenly goes from 100 to 50, that much cooler air will be going through the radiator. That coolant that is in the radiator will now be colder than previously. So when it leaves the radiator and goes to the engine, the thermostat will sense change in temperature. The thermostat will start to move towards the closed position in order to slow the flow down which will heat the coolant back up in order to maintain 194 degrees.

Now lets do the opposite of the above example. Say if the outside temp suddenly goes from 50 to 100. The thermostat is already more towards the closed position because of the cooler coolant entering the engine and the flow has to be slow because it has to heat it all the way back up to 194 degree. Now, as the hotter coolant enters the engine, the thermostat will sense the change in temperature and will start to move towards the open position in order to increase the flow through the radiator in order to maintain 194 degrees.

This opening and closing of the thermostat happens continuously as to maintain the temperature that its rated for as differences in outside temp, speed, and engine load change.

The vettes cooling system, (thermostat, radiator, and cooling fan), are DESIGNED to work TOGETHER as a MATCHED set. I believe the stock thermostat is 194 degrees F.

If the coolant moves too quickly through the radiator, then it will not have time to dissipate the heat into the air before going back into the engine.

Now, this is what happens when people change to lower temperature thermostats:

First of all and to make it clear again, the thermostat isnt just a simple on and off switch or is something that's just there to warm the engine up and then no longer plays any further role. Its a thermostat, and implies just what the term means. It continually moves toward the open or closed position in order to regulate the flow of coolant to maintain its designed temp rating. Just like the thermostat in your house, if you have it set to AUTO, then it will control the heater and a/c in order to maintain whatever temp you have it set at.

If you install a 160 thermostat, the engine will warm up just as quickly but only to 160 degrees initially. When the temp reaches 160, the thermostat will start to open to start the flow of coolant through the engine and radiator. As the engine continues to warm up, so does the coolant. The thermostat tries to maintain its designed temp rating by opening more to increase the flow into the engine to cool it down to 160. But the radiator wasn't designed to cool the coolant down that low. So as the coolant flows through the radiator, its not cooled enough by the time it leaves the radiator and goes back into the engine. So now the coolant in the engine continues to increase in temperature, so the thermostat senses the hotter coolant that was inadequately cooled by the radiator, it opens even more to increase the flow to cool it back down because the engine temp is increasing. But again the radiator wasn't designed to cool the coolant down that low. So now the thermostat is fully open and trying to cool the engine back down to 160 but it cant. And because of the thermostat now being fully open to allow more coolant in the engine in an attempt to cool it back down to 160, the flow through the radiator is too fast and cant dissipate the heat quick enough before entering back into the engine. This is why the engine temperature is always hotter when putting in low temp thermostats because the radiator isnt big enough to cool the coolant down that low. So most of the time youre running around with the thermostat fully open and the engine temp just varies all over the place with no consistency whatsoever because the flow of coolant is basically straight through at this point and the thermostat is unable to do its job. This is also why you read about people who put lower thermostats in and complain that it never runs at that temp and runs about 20 degrees hotter.

The cooling fans are only used when sitting still because there isnt enough airflow through the radiator. And yes the on/off settings will need to be adjusted if you insist on installing a lower temp thermostat and want to maintain the engine temp in that area.

The lower thermostat you put into your engine, the larger radiator you will need to compensate. A correctly designed and matched cooling system in a vehicle will be able to maintain the temperature of the thermostat regardless of the outside temperature, speed, or load being put on the engine. You dont want to run too cold of a thermostat because you want the oil to get to at least 190 to burn away any moisture, contaminants, etc. Me personally, I just stick with the stock thermostat (194 degree) and have the fans set to come on at 195 and I seem to make plenty of power just fine. See sig. My engine also maintains that exact 194 temp regardless of the outside temp, load on the engine etc. because its a matched setup. It will run more fuel efficient, emission efficient, and be internally cleaner.

I hope all this wasn't too confusing, I tried to make it as clear as I could."""

 

i just replaced my 99 with a 180 thermostat, i sit at 230 or 220, a guy that i work with just told me if i dont have the black air dam that sits under the bumper, he said that could be why. i replaced the resvor because it was leaking, and thermostat, still hot, so ill try the black scrapy thing under the bumper, put it on cus it came off a while ago. any other possibilitys?

 

Just use some Redline Water Wetter. That stuff works & you will run cooler.

 

You definitely have to have that lower center air dam. Its what directs air up into the radiator/a/c condensor cavity. Sitting still doesnt matter because your fans are running and will suck air up into the radiator, but its still going to run to the 220-230 range because thats where the fans are programmed from the factory. But when cruising down the road, the fans arent running and you have the air directed up into the radiator from the air dam, which should get you close to 180 with that 180 thermostat.

 

i cant drive with the air on here in cali , it his 240 the other day so i shut off the air and put it in nutruel and cruised to cool it down. do i need a programmer? or if i take it to Los Angeles Performance Division (thelapd.com) , he was going to dyno my car, maybe tune it, could i reprogram my fans???

 

While 240 is hot, its not overheating and is what its designed to do. And yes, if they dynotune your car, they can reprogram the fans.

 

last Q, ive never heard the fans turn on, are they just quiet? cus on the van my mom has, the v10 truck i have, all you can hear the fan, so i suppose mine is just quiet? i love my vette, but its just a headache now, constantly since i bought thecar, everything breaks, new wheel bearings, 400 each, roller rocker is ticking, so i gotta fix that, suspension is kinda ****ty, but mainly a bunch of **** that goes wrong is computer, then the resevor has to be replaced, thermostat, some other stuff so ill stop now. but either way, now im having this heating problem, so hopefully the airdam will help, and LAPD should be able to tune that for me like you said, thanks alot for your help ill try it out

 

Both fans run at the same time. They either both run at low speed or both run at high speed. You probably wont hear them running, especially in low speed, while in the car and the engine is running unless youre right beside the engine and perhaps with the hood up. Start the car and turn the a/c on, the fans should come on right away.

 

what part of "fully open" don't you understand ?

 

The guy who wrote "The Book "needs to go back to school...
First of all a 190 stat starts to open at 190, its actually closed at 190 guaranteeing the engine will get no colder than 190.. it is fully open at 197.
Heat transfer is NOT don't using the thermostat as the brain for the cooling system.
the PCM is the brain of the cooling system.. Once the stat is open and cooling temps are above 197, control of the temps below 35 MPH )56 kPh )are controlled by the PCM fan settings.

Depending on the model year...
For later model years:2001 and newer
The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).

For early model years:
Low speed fans come on at 219,high speed fans come on at 228,low speed with a/c on...

IN low speed conditions under 35 mph, the PCM controls the fans, which control the flow of air through the condenser and radiator vanes.
The PCM knows the car will see temps in the 220F 230 F range... and adjust accordingly. At any point above 198F the thermostat is completely out of the picture. Heat management is a product of air flow through the vanes under any condition .. below 35 mph wind shear caused by fan speeds moves air across the vanes to control coolant temps. When there isn't enough surface area and volume of cool air the coolant temp goes up... the stat has no Brain to control this..
People use a lower stat so they can create a wind shear at a lower temperature than the stock stat will allow...by lowering the fan settings...
if people do city driving most of the time and lower fan settings on a stock stat, the fans will never cycle on and off... they are designed to cycle on and off, tested to 80,000 cycles. you cant lower fan settings to 170 if the stat is coded at 190...
I've had inside information since 1996 on this issue...as most people already know.

 

Its idiotic crap like this is why I usually dont get into these threads. Im surprised you didnt add your irrelevant tire heat statements as well.

The PCM controls the fans, yeah, no kidding. The PCM is NOT the brain of the cooling system. If it werent for the thermostat, the engine temps would be all over the place. The fans are only used in slow or stop and go areas, NOT cruising down the freeway. The fans keep the engine from overheating at times when there isnt sufficient airflow and operate well above the thermostat temp rating, they are also for the a/c for the same reason. The fans come on obviously when the engine gets hot, and by that time the thermostat is wide open, the coolant has gotten hot and is unable to maintain the engine temp in the range of the installed thermostat. So now the fans come on in order to cool the coolant, but when the car starts to pick up speed again and there is ample airflow through the radiator, it starts to cool the coolant back down and then the THERMOSTAT MAINTAINS the temp of the engine, NOT THE PCM. The THERMOSTAT maintains the engine at the rated temp its designed by regulating the flow of coolant, NOT THE PCM. Tell me just how the PCM is going to regulate the flow of coolant?? IT DOESNT. Older cars with no PCM seem to have operated just fine. And like I meantioned above in my previous post, reading is fundamental, you should try it sometime. Below are just two quick statements that can easily be found on the internet as to the function of the thermostat.

EDIT: The service manual states that the thermostat BEGINS to open at 188 F and is FULLY OPEN at 206 F,,,,,NOT 190-197 as you stated.


FIRST SITE

""""""Thermostat
The thermostat's main job is to allow the engine to heat up quickly, and then to keep the engine at a constant temperature. It does this by regulating the amount of water that goes through the radiator. At low temperatures, the outlet to the radiator is completely blocked -- all of the coolant is recirculated back through the engine.
Once the temperature of the coolant rises to between 180 and 195 F (82 - 91 C), the thermostat starts to open, allowing fluid to flow through the radiator. By the time the coolant reaches 200 to 218 F (93 - 103 C), the thermostat is open all the way.

If you ever have the chance to test one, a thermostat is an amazing thing to watch because what it does seems impossible. You can put one in a pot of boiling water on the stove. As it heats up, its valve opens about an inch, apparently by magic! If you'd like to try this yourself, go to a car parts store and buy one for a couple of bucks.

The secret of the thermostat lies in the small cylinder located on the engine-side of the device. This cylinder is filled with a wax that begins to melt at around 180 F (different thermostats open at different temperatures, but 180 F is a common one). A rod connected to the valve presses into this wax. When the wax melts, it expands significantly, pushing the rod out of the cylinder and opening the valve. If you have read How Thermometers Work and done the experiment with the bottle and the straw, you have seen this process in action -- the wax just expands a good bit more because it is changing from a solid to a liquid in addition to expanding from the heat. """"



SECOND SITE

“””Question: What does the thermostat do?

Answer: The thermostat's job is relatively simple, but extremely important. It regulates the engine's operating temperature. It does this by restricting the flow of coolant from the engine back to the radiator. The thermostat is usually located in a housing where the upper radiator hose is connected to the engine. The thermostat is a valve that is held shut by spring tension. A wax filled thermal element in the thermostat opens the valve. As the engine begins to warm up and the coolant gets hot, the wax inside the sealed element expands and pushes the thermostat valve open. This occurs at a preset temperature (typically 195 degrees F. or so), which is usually stamped on the thermostat itself. The thermostat should be fully open about 20 degrees F. above the rated temperature.
The opening of the thermostat allows coolant to circulate through the engine and cooling system. As the temperature of the coolant begins to drop, the wax element cools off and contracts allowing the thermostat to partially or fully close. Thus, by cycling open and shut a relatively constant operating temperature is maintained.”””

 

Not fully true. It works, but with plain water only. When you got 50/50 Dexcool and water might as well not add Water wetter. It wont make a difference either way..

 

WOW my head now hurts... This is why I only use this as a reference to find get an idea of how things work. I love this forum but it really contradicts itself because people always swear they are the only ones that can possibly be right.

 

I love it! Temperature, thermostat, overheating threads never fail to bring opposing opinions and protagonists. It's almost as good as the cold air intakes debates.

Here's my opinion (like a--holes, everybody has one and they, well you know). Clean the junk out of the A/C condenser and the radiator fins and drive the car. The engine was designed to operate in the 195-230F range under normal conditions. It's aluminum with a high coefficent of heat transfer, not cast iron.

Chevy gave people too much info on the Vette. They need a gauge that has C and H and a needle that stays in the middle, then you wouldn't have all these posts.

 

good post George.
I have cut way back on giving advise in open forum, for just these reasons... being on the ''inside'', I know the answer to many C5 questions, especially those around the cooling system.. what brings me out of Private messages,and into open forum is the writer "of the book" types...with all their BS based on cooling system technology of the 60's. Back when the water pump was the front motor mount on a corvette. I have to learn to control myself..
ET

 

LOLOLOL, blah blah, whatever.

Tell you what, tell me where im wrong and back it up with some sources, links, text copy pasted from a service manual or any other documents, etc. I will be waiting.

the book writer

 

 

Does that also include writing a response without a good grasp of how to use the English language? Ever hear of maybe setting somebody straight with good info without having to be an a$$?

I know, I know, I'm a newb to this board, but sheesh...

R/
Dustin

 

Evidently, you didn't bother to read E-T's posts on the subject where he did present good info based on his years of Corvette experience, but your ego obviously was injured by his remark. So now you consider him an *** and attack his use of the English language. Pretty immature response, if you ask me.