ENGINE GETS RED HOT
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Mace Canute
Elite Member
The "water flows too fast through the radiator to give up heat" statement is an myth. The thermostat acts as a variable restrictor to flow and since there is a pump on the other end of the block, the pressure in the block rises. (This isn't a small increase in pressure either). This increase in pressure prevents the formation of small, localized steam pockets. Removing the thermostat removes the restriction and doesn't allow the pressure in the engine to rise enough to prevent the formation of the steam pockets. Any place where there is a small little steam pocket, there is very little transfer of heat. The metal reaches a higher and higher temperature and in the areas where there is transfer, the coolant raised to much higher temperatures. The effect cascades. A fast flow will scrub off steam bubbles as they appear in the hottest parts of the engine before they have a chance to congregate into an impenetrable steam pocket.
Localized heating may also cause detonation in gas engines, which in itself can also quickly cause overheating.
Years ago a company that specialized in making water pumps for racers did some tests to optimize their pumps for the application and they built their own test systems to accurately measure exactly what was happening rather than rely on the beliefs of others. They measured the flow rates, pressures in various parts of an engine and the temperatures involved plus a few other things. Quite involved. One thing that I remember very well is their finding that you could not flow the coolant through the radiator too fast! Too slow, yes, too fast, no! A slow flow allows laminar flow to occur which means the outside of the coolant flowing through a tube remains in contact with the tube and the inner center portion doesn't. That means the inner portion does not give up heat as well since it is insulated by the outer portion of coolant. A faster flow induces turbulence which means all the coolant directly touches the radiator tube and therefore more heat is transferred.
As a wise man once said..."Don't believe everything you know."
Localized heating may also cause detonation in gas engines, which in itself can also quickly cause overheating.
Years ago a company that specialized in making water pumps for racers did some tests to optimize their pumps for the application and they built their own test systems to accurately measure exactly what was happening rather than rely on the beliefs of others. They measured the flow rates, pressures in various parts of an engine and the temperatures involved plus a few other things. Quite involved. One thing that I remember very well is their finding that you could not flow the coolant through the radiator too fast! Too slow, yes, too fast, no! A slow flow allows laminar flow to occur which means the outside of the coolant flowing through a tube remains in contact with the tube and the inner center portion doesn't. That means the inner portion does not give up heat as well since it is insulated by the outer portion of coolant. A faster flow induces turbulence which means all the coolant directly touches the radiator tube and therefore more heat is transferred.
As a wise man once said..."Don't believe everything you know."
wvpolekat
Platinum Member
BINGO! The description is not good enough. It sounds like someone put their hand on it to see if it was too hot. Need to put a gauge on it to be sure.
sweettractors
Advertiser
We need more info about the specifics of this particular situation to help from here in. Ken Sweet
Bear Foot Farm
Silver Member
That defies several laws of Physics, since it's ALL coolant, and incapable of "insulating" itself
Heat transfers faster through a liquid than a solid, and flows from hot to cool whether there is turbulence or not.
In fact the heat transfer itself causes convection currents
The only reason the engine will over heat with the stat out is that the problem wasn't the stat in the first place
if the engine isn't moving coolant or the rad is the prob
lets face it when the engine gets above to operating temp the stat OPENS to allow coolant to flow around the radiator then when the rad has done its job the stat closes or restricts the flow
so open is more cooling than closed
Anyway i rebuilt an old landrover engine a few years back and my brother and dad fired her up the first time and told me it was to hot so stopped it turned out that it was just the new paint on the block if it smells hot that doesnt mean it is only a good temp guage will tell you for sure
and there is allways a bit oil some were that needs a min or to to burn off:thumbsup:
if the engine isn't moving coolant or the rad is the prob
lets face it when the engine gets above to operating temp the stat OPENS to allow coolant to flow around the radiator then when the rad has done its job the stat closes or restricts the flow
so open is more cooling than closed
Anyway i rebuilt an old landrover engine a few years back and my brother and dad fired her up the first time and told me it was to hot so stopped it turned out that it was just the new paint on the block if it smells hot that doesnt mean it is only a good temp guage will tell you for sure
and there is allways a bit oil some were that needs a min or to to burn off:thumbsup:
Eagleview
Veteran Member
An engine that is lightly loaded , a pickup for example with a Thermostat removed will run cold and experience cylinder glazing .
An engine that is worked hard like a semi pulling up a steep grade with no Thermostat will run hot . It is a fact that the extremely hot combustion process super heats the water around the cylinder liners and head , the water is circulating too fast and does not spend enough time in the radiator core to allow dissipation to fully occur . This already hot water then goes back to the block and gets another dose of heat so the problem increases exponentially until it overheats .
If a Thermostat fails , do not remove it completely , instead remove the center section and put the outer disc back in place . This will give you the correct size orifice which slows the flow to that of an open Thermostat , the engine will just take longer to warm up . This is only to get you home , replace with the correct temp unit to suit your climate as soon as possible .
Make sure the Thermostat is installed the correct way , the bulb faces the engine and the heated water . I have seen them in back too front , the bulb is in the cold side and will not open and the engine will boil .
An engine that is worked hard like a semi pulling up a steep grade with no Thermostat will run hot . It is a fact that the extremely hot combustion process super heats the water around the cylinder liners and head , the water is circulating too fast and does not spend enough time in the radiator core to allow dissipation to fully occur . This already hot water then goes back to the block and gets another dose of heat so the problem increases exponentially until it overheats .
If a Thermostat fails , do not remove it completely , instead remove the center section and put the outer disc back in place . This will give you the correct size orifice which slows the flow to that of an open Thermostat , the engine will just take longer to warm up . This is only to get you home , replace with the correct temp unit to suit your climate as soon as possible .
Make sure the Thermostat is installed the correct way , the bulb faces the engine and the heated water . I have seen them in back too front , the bulb is in the cold side and will not open and the engine will boil .
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Mace Canute
Elite Member
Apparently you can lead a horse to water............
Raspy
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There are two issues here. The "red hot" engine and thermostat theory.
I am responding to some of the statements about thermotats.
The thermostat "controls" the temp of the engine. If it ever does get fully open, it is a similar situation to not being there at all. In other words, no stat equals wide open stat, which equals maximum cooling.
There is no such thing as having to let the water sit in the block to remove the maximum amount of heat. Fast turbulent flow with a minimum increase in temp per pass removes the maximum energy from the engine. This is because turbulent flow exposes more of the water to the hot surface and breaks up the film of water next to the surface. It flows in areas that might not if the volume is very low. It is also because maximum heat transfer occurs with the greatest differential in temperatures. This is basic physics. A hotter surface flows more BTUs to a colder fluid than to a hotter fluid.
Remember, we are not trying to heat the water, we are trying to cool the engine, that is once the engine is up to temp. The colder the outflowing water is, the more energy removed. You get cooler outflow by increasing the volume. BTUs is stated in volume and temp difference. Another way of looking at it is to imagine if the water enters the engine cool and exits hot. Some of the block is exposed to cool water and some of it is exposed to hot water. The hot water will remove less energy because the block and water are closer to each other in temp. The water can only go to it's boiling point and then it cannot except anymore energy (past the latent heat of fusion) before it simply becomes steam and practically worthless as a coolant.
Bottom line is the engine will run colder with no thermostat. Often much colder and not last as long or run as efficiently. It cannot ever come up to temp unless working hard. It's always running at max cooling.
I am responding to some of the statements about thermotats.
The thermostat "controls" the temp of the engine. If it ever does get fully open, it is a similar situation to not being there at all. In other words, no stat equals wide open stat, which equals maximum cooling.
There is no such thing as having to let the water sit in the block to remove the maximum amount of heat. Fast turbulent flow with a minimum increase in temp per pass removes the maximum energy from the engine. This is because turbulent flow exposes more of the water to the hot surface and breaks up the film of water next to the surface. It flows in areas that might not if the volume is very low. It is also because maximum heat transfer occurs with the greatest differential in temperatures. This is basic physics. A hotter surface flows more BTUs to a colder fluid than to a hotter fluid.
Remember, we are not trying to heat the water, we are trying to cool the engine, that is once the engine is up to temp. The colder the outflowing water is, the more energy removed. You get cooler outflow by increasing the volume. BTUs is stated in volume and temp difference. Another way of looking at it is to imagine if the water enters the engine cool and exits hot. Some of the block is exposed to cool water and some of it is exposed to hot water. The hot water will remove less energy because the block and water are closer to each other in temp. The water can only go to it's boiling point and then it cannot except anymore energy (past the latent heat of fusion) before it simply becomes steam and practically worthless as a coolant.
Bottom line is the engine will run colder with no thermostat. Often much colder and not last as long or run as efficiently. It cannot ever come up to temp unless working hard. It's always running at max cooling.
woodlandfarms
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On the thermostat issue, this is how I learned it from a NASCAR engine team (I have had the good fortune of being around them a number of times)...
The thermostat is designed to heat an engine first, then control cooling. All thermostats do not flow at 100%, they have a certain amount of restriction.
This restriction is beneficial at the coolant pump, it keeps the pump from cavitating. Yes, engine can overheat from not having a thermostat (but you would have to be running a very high RPM machine) none the less it can and does happen.
Carl
The thermostat is designed to heat an engine first, then control cooling. All thermostats do not flow at 100%, they have a certain amount of restriction.
This restriction is beneficial at the coolant pump, it keeps the pump from cavitating. Yes, engine can overheat from not having a thermostat (but you would have to be running a very high RPM machine) none the less it can and does happen.
Carl
kenstrac
Platinum Member, RIP
This restriction is beneficial at the coolant pump, it keeps the pump from cavitating.
It also keeps the engine flow from caviting and causing hot spots in the engine.
It also keeps the engine flow from caviting and causing hot spots in the engine.
rjkobbeman
Platinum Member
The backyard theories here are just priceless. An engine will NOT run hot if the thermostat is removed. Those stating the water pump will cavitate need to go read about cavitation. Cavitation, if possible in a given water pump, would occur when flow is restricted... not maximixed. Flow would be maximized if the thermostat was removed.
kenstrac
Platinum Member, RIP
BACKYARD? after rebuilding 3 different engines (block cracked from top to crankshaft) was told by service manager that engine cold not be run w/o thermostat internal cavitation caused hot spots in engine.
wvpolekat
Platinum Member
Ok boys and girls.
Just because YOU haven't seen something happen doesn't mean that I can't happen.
Just because YOU saw something happen, that doesn't mean that is what will always happen.
I have seen cars without a thermostat run just fine (cold), I have also seen cars that would overheat without one.
There are too many variables for any of us to make black and white statements about what will or will not happen without a thermostat. Load on the engine, overall condition of the cooling system, layout of the water jackets in the block/head, head/block material, mineral deposits, size and design of radiator. All of these things could have influence on how the cooling system acts when operating outside of how it was designed.
So, there is no "right" answer here.
Just because YOU haven't seen something happen doesn't mean that I can't happen.
Just because YOU saw something happen, that doesn't mean that is what will always happen.
I have seen cars without a thermostat run just fine (cold), I have also seen cars that would overheat without one.
There are too many variables for any of us to make black and white statements about what will or will not happen without a thermostat. Load on the engine, overall condition of the cooling system, layout of the water jackets in the block/head, head/block material, mineral deposits, size and design of radiator. All of these things could have influence on how the cooling system acts when operating outside of how it was designed.
So, there is no "right" answer here.
Cavitation is linked to the boiling point of a liquid at a given temperature and pressure. Water boils at 212 Deg. F at sea level, move to the Rockies and the boiling point falls to 198 Deg. F.
Now, how do we lower the boiling point of a liquid inside an engine? Simple, restrict the flow not by forcing the liquid through a small passage which will increases the pressure but rather drawing [suction] the liquid through a small passage reducing the pressure to below that which the liquid would normally boil. That is why the maximum lift on the suction side of a water pump is limited to 32 feet.
Yes, it is counterintuitive, however there may be locations in the flow path that satisfy the conditions for cavitation.
One way to offset a low pressure point is to raise the overall pressure within the cooling system, hence the pressure cap for the radiator, at 15 psi above atmospheric pressure the boiling point of water is 230 Deg. F. In addition, adding antifreeze to the water increases the boiling point too.
Now, how do we lower the boiling point of a liquid inside an engine? Simple, restrict the flow not by forcing the liquid through a small passage which will increases the pressure but rather drawing [suction] the liquid through a small passage reducing the pressure to below that which the liquid would normally boil. That is why the maximum lift on the suction side of a water pump is limited to 32 feet.
Yes, it is counterintuitive, however there may be locations in the flow path that satisfy the conditions for cavitation.
One way to offset a low pressure point is to raise the overall pressure within the cooling system, hence the pressure cap for the radiator, at 15 psi above atmospheric pressure the boiling point of water is 230 Deg. F. In addition, adding antifreeze to the water increases the boiling point too.
BSawyer
Member
Does this illustration make sense?
Say, you just finished mowing on July 3rd and you want some liquid refreshment. If you want to cool down your "room temperature" drink in a hurry, would you use one large cube of ice or crushed ice? answer: crushed ice. why? because it has much more surface area to allow the thermal transfer and cool down your beverage faster, right?
It is the same with the radiator versus engine block. All the fins and thin passages of the radiator are way more efficient at heat transfer than the passages and thick walls in an engine block. So whatever heat is created in the block is quickly dissipated via the radiator passages when it passes thru the radiator. The thermostat slows the coolant down in the engine (or stops it?) so that the engine can warm up to correct op temp.
Now say you like your drink really cold, do you get more thermal transfer by letting it sit still with ice in it, or stirring the crushed ice in the drink rapidly, as you might do with iced tea?
Ever used a hand crank ice cream maker? Do you just add ice and wait for ice cream to form, or crank and spin the cream in the ice mixture til your turn is over and you pass it to someone else for a while?
Wouldn't coolant moving rapidly thru a radiator act similarly? Hot engine block >--> cool radiator. Transferring heat.
I used to have one of the old (1980?) Oldsmobiles Custom Cruiser wagons that GM put their sorry designed 350/v8 diesels in, and when it died an early death as often happened, the previous owner replaced with a bolt in gas engine swap. When the thermostat was out in the winter, you could not get it to warm up or produce any heat from the heater core. I'm guessing, purely guessing, that GM must have put a HD radiator in those cars. (* quick search of AZ shows it was a bigger rad in the 350 diesel vs 350 gasser)
Long story short, the radiator was much too efficient for the engine without thermostat. The engine did not get hot, needle stayed buried on the cold side, without thermostat.
Just trying to add another .02 for the thread.
ChiefRichard, I hope you find it is just something simple as others suggested like paint or oil that was being burned off. Get a temp gauge to know for certain.
Say, you just finished mowing on July 3rd and you want some liquid refreshment. If you want to cool down your "room temperature" drink in a hurry, would you use one large cube of ice or crushed ice? answer: crushed ice. why? because it has much more surface area to allow the thermal transfer and cool down your beverage faster, right?
It is the same with the radiator versus engine block. All the fins and thin passages of the radiator are way more efficient at heat transfer than the passages and thick walls in an engine block. So whatever heat is created in the block is quickly dissipated via the radiator passages when it passes thru the radiator. The thermostat slows the coolant down in the engine (or stops it?) so that the engine can warm up to correct op temp.
Now say you like your drink really cold, do you get more thermal transfer by letting it sit still with ice in it, or stirring the crushed ice in the drink rapidly, as you might do with iced tea?
Ever used a hand crank ice cream maker? Do you just add ice and wait for ice cream to form, or crank and spin the cream in the ice mixture til your turn is over and you pass it to someone else for a while?
Wouldn't coolant moving rapidly thru a radiator act similarly? Hot engine block >--> cool radiator. Transferring heat.
I used to have one of the old (1980?) Oldsmobiles Custom Cruiser wagons that GM put their sorry designed 350/v8 diesels in, and when it died an early death as often happened, the previous owner replaced with a bolt in gas engine swap. When the thermostat was out in the winter, you could not get it to warm up or produce any heat from the heater core. I'm guessing, purely guessing, that GM must have put a HD radiator in those cars. (* quick search of AZ shows it was a bigger rad in the 350 diesel vs 350 gasser)
Long story short, the radiator was much too efficient for the engine without thermostat. The engine did not get hot, needle stayed buried on the cold side, without thermostat.
Just trying to add another .02 for the thread.
ChiefRichard, I hope you find it is just something simple as others suggested like paint or oil that was being burned off. Get a temp gauge to know for certain.
Jim Thompson
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Is the horse dead yet? :laughing:
Egon
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It may be Dead but still needs to be buried!:laughing:
some zilch
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i'll be that guy that keeps bringing it back.......
i take both (thats right, both) thermostats out of my 3406 powered peterbilt in the summer, both to help keep it a bit cooler, but mostly it really seemed to maximize a/c output. if it got chilly in the fall before they were back in, the engine would never warm up to op temp on the highway, even fully loaded.
i take both (thats right, both) thermostats out of my 3406 powered peterbilt in the summer, both to help keep it a bit cooler, but mostly it really seemed to maximize a/c output. if it got chilly in the fall before they were back in, the engine would never warm up to op temp on the highway, even fully loaded.
