How hot is cool enough?

[Steve Jelf]

Argument on FB.
Other guy: The thermosyphon system is designed to boil.
Me: No, boiling is a sign of something wrong.
Blah, blah, blah...
Is one of us right?

[Norman Kling]

`No! It is devised to cool the engine. The engine will get hot without any coolant or water but the coolant gets hot as it circulates through the engine and then as the radiator cools it, it will flow downward through the radiator and cycle through the engine again. If it is clean and full it works very efficiently. A water pump will circulate the coolant through the system too fast and needs a thermostat to keep the temperature at the operating temperature. Henry designed the Model T to save money by using the law of thermodynamics to cool the engine and did a very good job at it.
Norm

[Wayne Sheldon]

The remarkable and incredible thing about the thermosyphon system is that if the engine is cold, there isn't enough temperature difference between the engine and the radiator, causing the water to move slowly, which in turn allows the engine to warm up to a more efficient operating temperature. While it may not be as accurate as a thermostat, it does a remarkable job of regulating the engine's temperature and keeping it at a fairly efficient operating temperature at most common weather conditions. In extreme cold, it is necessary to restrict the air flow through the radiator to prevent freezing of the water inside (modern antifreeze also helps!). Pretty much just like a modern engine with a thermostat.

[bobt]

I say no boil but right at the point of boiling. I judge mine by always being able to hold my hand on the water return pipe going back to the block.

[Charlie B in N.J.]

Pretty much an open to the air system so boiling would cause coolant to leave in the form of steam. Boiling is a no no.

[Loftfield]

But when? On an average day after an average drive, no boil. However, if air temp is very high, or after a long slog up a good hill, the system may boil if the engine is stopped, hence the advice to not shut off at the top of the hill but let the engine idle until the temp comes down.

[NealW]

Argument on FB.
Other guy: The thermosyphon system is designed to boil.

IMO, people need to look at the Ford owner's manual and/or the service manual FIRST if they have a question and then pose the question on FB or the forum site IF their answer can't be found. The original manual is very unique in that so much of it is written in a question and answer format that answers most major questions and provides basic troubleshooting methods that are still helpful today.

Here's what the owner's manual says about the cooling system and boiling:

[Kaiser]

Water is excellent at transfering heat, which is what you want, get the heat out of the engine to the radiator. Steam not so much, so boiling is not good as the pockets of steam occur first at the hottest spots in the engine, just where you need heat transfer the most.
Hope this helps to 'win' the argument Steve.
By the way; good to see you here on the forum regularly again !

[DanTreace]

And with a low cost infrared temp gauge, you can test the system for efficient cooling, did that on a typical warm 90 degree FL day.

Pointed the infrared at the upper tank under the hood, and on the lower metal return pipe from the radiator.

Start point, T in garage, upper tank at temp of around 82.

Drove around to warm to operating temp, about 2 miles and stopped with engine idle and pointed infrared at backside of the upper tank , right at normal operating temp.

Then pointed at the lower pipe and temp was much lower, about 62 degrees difference, can touch that pipe as not too hot, of course don't touch that upper tank

Added bonus, with running also a motometer, that confirmed the operating efficiency too, normal reading for summer!

[TXGOAT2]

The system should not boil, for reasons cited above. Proper use of the spark and mixture controls under demanding conditions will prevent boiling. The system will continue to circulate coolant when it is hot, even with the engine not running. Most all boiling situations are due to a dirty system or defective radiator or oiling issues. An exception to that is operating at higher altitudes, which will allow coolant to boil at a lower temperature than otherwise. Reducing the load on the engine under extreme conditions is always a good idea, where practical. Almost anything that reduces the engine's power, such as leaky valves, ignition problems, worn rings, or improper use of spark, carburetor, and throttle controls will promote overheating. Anything that adds to the engine's load, such as dragging bands, under-inflated tires, overloading, oversize bodywork, or pulling a trailer will increase the chances of overheating. Keeping the engine and radiator clean helps prevent overheating. Late timing will cause the engine to run hotter and will promote "afterboil" due to the exhaust manifold running even hotter than normal. It will cause the exhaust valves to run very hot, and will put needless thermal stress on the exhaust valve seats.

[TXGOAT2]

180 to 195 F is a good operating range when using plain water. With 50/50 green antifreeze and modern, quality motor oil, plus 80+ octane fuel, the T engine can safely run at higher temperatures as long as the coolant doesn't boil. 200 to 220 F at the water outlet will not harm the engine when using modern motor oil. Higher running temperatures reduce carbon deposition in the combustion chambers and prevent sludging in the crankcase.
Ideally, a T running at high altitudes or under very heavy loading would be equipped with a custom radiator and a 10# pressure cap with an overflow tank.

[John Codman]

There is a reason that modern automotive cooling systems are pressurized. That reason is to keep the coolant from boiling. Boiling coolant doesn't remove heat efficiently. A model T with a properly operating cooling system should never get even close to boiling. My 27 doesn't even get to 180 Deg here in SW Florida. If all of the components are in good shape, a T shouldn't boil.

[signsup]

To answer the OP's question . . . yes, one of you is right.

Now, my question . . . which one?

Wonder what temp's the motometers are set to read?

[TRDxB2]

The thermosyphon action is based on a density differential. As water is heated it becomes less dense. Example: the air bubbles that begin to form in a pot of water on the stove. In the cooling system the hot fluid begins to rise and float above the cooler fluid. This action, in effect pushes the fluid into the radiator where gravity and capillary action causes the fluid to fall as it cools in the radiator. The action is also dependent on atmospheric pressure.

If the water turns to steam its supposed to condense in the tank on top of the radiator...but some may leak out through the overflow tube. The loss of fluid will eventually stop the flow reaching the radiator.

The greater the density differential the faster the flow. I couldn't find what "density" differential would trigger the thermosyphon action.
12°C = 53.6°F

[Norman Kling]

Some people remove the fan belt. As long as you are running at speed into the wind, the radiator will work fine without the fan but if you idle for long, it will overheat. The fan is necessary for stop and go driving. A good radiator with clean engine and radiator will not overheat in hot weather. Even the paint on the radiator should be a very thin coat so it does not affect the cooling. On a hot day going up a steep hill the engine should not overheat but if you turn it off right after pulling the hill it might gurgle for a few minutes.
The first T I got had a water pump on it when I bought it. One of my first tours we took into the mountains. There was some snow on the ground and quite cold. When we parked many of the members were standing in front of their radiators to keep warm. My car was still cold! Later I removed the water pump and it worked like it should.
Another problem is the honeycomb radiator, which is not Ford but aftermarket. It must be kept clean and sediment free because it can only be boiled out. It is impossible to rod out a honeycomb radiator.
Norm

[Steve Jelf]

...people need to look at the Ford owner's manual and/or the service manual FIRST if they have a question and then pose the question on FB or the forum site IF their answer can't be found.

Guilty as sin, Your Honor. I can be as lazy as anybody else.

[TXGOAT2]

The T system is NOT designed to boil and it does NOT depend on boiling, bubbles, or any such thing to circulate the coolant.
Some old stationary engines were "hopper cooled", which used an open water jug cast with the water jacket and no radiator. These would boil under load, and water had to be added frequently when the engine was working. Another type of system was very similar to the thermo syphon, but differed in that the water outlet to the water tank was above the level of the water. These systems would typically boil under load and "burp" water and steam into the water tank. Another type of system added a condenser to the hopper cooled arrangement. The condenser typically looked much like a radiator, but it was not filled with liquid. Steam from the hopper would rise into the radiator-like condenser and condense back into water and drop back into the hopper. This saved water and reduced mineral deposition and oxygen entrainment. Screen-cooled systems were also used, where hot coolant ran down over a screen and back into the cylinder. These probably needed less water than a tank cooled system and thus weighed less, making them better suited for a portable engine. A tank cooled engine of any size needed a fairly large water tank. The thermosyphon system with a radiator is the only one of these systems suited for use in an automobile.

[NealW]

Guilty as sin, Your Honor. I can be as lazy as anybody else.

My response was meant for the "other guy" type of posters!

I still learn things from the T owner's manual every time that I reread it. It's 110+ year old information that still will help keep current Model T owners out of trouble if they take the time to read it!

[bobt]

My 1915 T touring came with a water pump. I removed when I replaced the round tube radiator with a Brassworks flat tube radiator. The water pump didn't have an impeller but it had a little S shaped paddle. There is no way in the world that it could have pumped water. I does make a good wheel chock though.

[TXGOAT2]

It probably moved some water, at least at higher engine speeds. A real water pump with a larger impeller would risk causing cavitation and could cause the radiator to overflow, especially if the radiator was restricted. On the Model A, the water pump was meant to assist the thermosyphon flow in what amounted to a hybrid system. A Model A in good condition could run indefinitely at moderate speeds under most conditions with no fan belt. It's best to pull cool water from the radiator outlet and pump it into the block rather than pull hot water from the cylinder head outlet, but Ford under Henry's control wanted to maintain at least some thermosyphon action. Up through 1948, the V8s had tall radiators and very large water hoses with the water outlet located at the upper center of the cylinder heads, which could provide some coolant circulation if the water pump drive belt failed.

[RajoRacer]

Water pump is a bit of a misnomer - they're more of a circulator than a pump.

[TXGOAT2]

More of a "booster" meant to "pep up" the water flow... not needed on a *Model T in good condition under any but extreme conditions. As I understand it, they were as much a cold weather accessory as a hot weather one, since a water pump could prevent the radiator from freezing when out on the road in bitter cold weather... as long as the engine was running. A water pump might be useful on a TT in a hot climate.

The Model A Ford of 1928-31 had a rudimentary water pump in what amounted to a hybrid thermosyphon-pump system. The majority of the 15 million Model Ts had no water pump and no need of one.
It's worth noting that the Model A engine made twice the power of the T engine from about the same displacement, and the Model A cars outweighed the T, and were capable of sustained higher road speeds.

[Jerry VanOoteghem]

On the Model A, the water pump was meant to assist the thermosyphon flow in what amounted to a hybrid system.

....Ford under Henry's control wanted to maintain at least some thermosyphon action.

Pat,

You seem to state these points as fact. Are they actually supported by the historic record, or are they your conjecture?

[jiminbartow]

IMG_1256.jpeg (65.05 KiB) Viewed 5722 times

[John E. Guitar]

Neil's post covers the original question, but it's worth remembering that when the radiator boils you are getting nucleate boiling which gives very good heat transfer.

[Kaiser]

John, I don't know where you found that picture but your graph is for a very different situation, i.e. a drop of water dropped on a surface of a certain temperature, it has little relation to a motor and radiator system filled with water that heats up while under power. What it does show however is that as soon as the water comes up to a fierce boil (transition boiling), heat transfer from metal to water drops off sharply.
The 'film boiling' part does not occur in an engine filled with water, at that point it is allready a lot hotter than it should ever get. it only happens when you drop some water on a hotplate, it is the droplets sizzling and scooting of in all directions. It could happen if most water in your engine boiled off and you re-fill the hot and dry engine with water without waiting for it to cool off, not a good thing to try, you might crack a head or a block.

[John E. Guitar]

Here is some more information on nucleate boiling in an automotive context.

https://archive.org/details/introductio ... 6/mode/2up

[TXGOAT2]

Anyone who has access to a Model T in good operating condition can prove that the cooling system circulates water or other suitable coolant WITHOUT boiling. The T system will begin to circulate coolant at about 180F, according to Ford, and coolant circulation will prevent boiling anywhere in the engine if the system is operating properly. An exception might occur at very high altitude and full power operation, however, altitude would also reduce power output and thus reduce demand on the cooling system. Anyone operating a T at high altitude would do well to add green antifreeze to raise the boiling point of the coolant to prevent steam bubbles around exhaust valve seats.

The Model A system will perform the same way as the T with the fan belt removed, and can adequately cool the engine at lower power output levels absent the fan belt. Murray Fahnstock, a period expert and advocate on Ford cars, discussed this and other virtues of the Model A in a book about the Model A. Model A owners can demonstrate that the cooling system can function, at a reduced level, without the fan belt in place.

How a drop of water behaves in a hot skillet does not correlate directly to how coolant behaves in an atmospheric thermosyphon system.

[TXGOAT2]

Unlike a hopper-cooled system, the Model T system does not depend on vaporization (boiling) of the coolant to function. It depends upon the thermosyphon principle and the high heat-carrying capacity of water to transport heat from the engine to the radiator, where the heat is dissipated into the flow of air through the radiator.

The hopper cooled system depends primarily upon the very large amount of heat required to vaporize water under atmospheric conditions to rid the engine of waste heat, and boiling under sustained load is expected. The advantages of the thermosyphon system with a "radiator" in automotive applications are obvious.

[Craig Leach]

I do not want to contradict anyone or add to the controversy on the principles of thermosyphon but I discovered something earlier this year
when running in a engine refresh. ( was not bored & no rebabbitt ) Ringed, valves & trans replaced. I run everything for 2-3 hours on the test
stand to make sure everything is ready to go & broke in when installed. I have a piece of clear hose on the upper radiator hose. I run water
circulators on my engines because I expect more out of my T 's engine than most do. The last engine the one mentioned does not have a water circulator on it. I noticed @ about 180* it started to form bubbles in the upper hose by 190* they were rather large & plentiful. I don't run in
engines over 200* so I shut it off. The bubbles continued to rise into the radiator for a minute or so with the engine off. There was no gurgling
or steaming as it never reached boiling. This is not seen on a engine with a water circulator that I have ever noticed ( previous 3 anyway )
I have a video but I have not been able to edit it enough to post it. When I first seen this I thought I must have had a lot of air in the system
but this occurred every time it was run over the next 3+ hours. One would suspect that these bubbles are formed by small pockets of water
coming to a boil in the engine before the majority of the water does but these bubbles move a a very rapid speed & I would think they would
carry cooler water with them aiding in the cooling prosses. So the thought that boiling water aids in the thermosyphon process may hold water.
Pun intended.
Craig.

[TXGOAT2]

Heat will drive dissolved gases out of water, and probably out of dry iron, too. That effect shouldn't last long, however. Higher altitudes reduce the boiling point of water substantially and can allow boiling well below 212F, which is pure water's boiling point at sea level. Some water contains more dissolved gases than other, and some water contains minerals that may react when it is first heated. The slightest leak of combustion gases will cause bubbles, both by entrainment of bubbles and by chemical reactions.

[jiminbartow]

Craig. Did you have a high speed hurricane fan set up in front of the radiator to simulate the forward movement of the car? If not,I would be interested in knowing if it makes a difference on your findings.

[Craig Leach]

Hi James,
This particular engine is out of a single seat racer that has a unique ignition system that fits were the fan would be & has a electric fan on the
radiator. My test stand has a old round tube low radiator that is not that great. I did have a pedestal fan in front of the radiator. I have found
many fresh engines run a little warm @ first. so there was no concern about the temp other than not letting it get over 200* so when the out
coming water was @ 200* the water returning to the engine was 160* - 170* I would shut it off let it cool down & check & retorque as needed.
The last run it reached 195* & stabilized there for 20 minutes @ that time I had more than 3 hours on it so I shut it off drained the oil, when it
cooled down drained the water & put it away till the car is ready to have the engine installed. I just never seen the bubbles in the upper hose
like that with a water circulator so I figured that is just part of the thermosyphon process & was wondering if that had been observed by anyone
else. The perception everyone has seems to be a homogenous flow of coolant. I guess no one has tried a clear hose for testing or just for
curiosity.
Craig.

[varmint]

Oh my! Guys, tell me no one has ever seen a pot of water on the stove, forming bubbles at the bottom, long before a hard boil. A cooking thermometer clearly shows what's going on. Some of those tiny bubbles make it to the surface. Can you see water flow? Yes, sometimes as surface wakes.

[TXGOAT2]

The water will begin to stir even before the bubbles form on the bottom of the pan. Most water is not pure, and most people do not live at sea level, and most water contains at least some dissolved air, which heat will tend drive out of it in the form of bubbles. So 212F as the boiling point will not strictly apply. The water in a pot or skillet will not heat evenly, especially in a lightweight vessel. It will be hottest at the point where applied heat is greatest, and the heated water will rise and be replaced by cooler water. Once boiling commences, mechanical agitation will disrupt the thermosyphon action. Boiling is to be avoided in cooling systems, except for the hopper type and the "Geyser" type, where boiling is expected to occur.

[Drkbp]

Vernon,
Yes you are correct. Here is a 1914 that sat idling on my driveway for an hour.
Kitchen thermometer.

[TXGOAT2]

Even in August, ponds and lake around here will have much cooler water in the deeper parts. This is true even when the surface water is quite warm. Diving to eight or ten feet will usually put you in water that actually feels cold. The cold water stays on the bottom because it is denser and heavier than the warmer water near the surface.

[TRDxB2]

The thermosyphon action is based on a density differential. As water is heated it becomes less dense. Example: the air bubbles that begin to form in a pot of water on the stove. In the cooling system the hot fluid begins to rise and float above the cooler fluid. This action, in effect pushes the fluid into the radiator where gravity and capillary action causes the fluid to fall as it cools in the radiator. The action is also dependent on atmospheric pressure.

If the water turns to steam its supposed to condense in the tank on top of the radiator...but some may leak out through the overflow tube. The loss of fluid will eventually stop the flow reaching the radiator.

The greater the density differential the faster the flow. I couldn't find what "density" differential would trigger the thermosyphon action.
12°C = 53.6°F

Just to review what I had posted earlier. I used the air bubbles as an EXAMPLE to show how the water was becoming less dense as the temperature increases. For thermosyphon to cause "flow", the fluid being heated needs to expand. As the heated fluid expands, the fluid level in the engine determines the point at which circulation actually occurs as it needs to flow into the radiator. A second effect also occurs as the surface tension of the heated fluid is lessened making it easier to flow through the radiator core.

[nsbrassnut]

Just a comment, similar to those posted earlier.

I was out on a 90 km (about 50 mile) tour on Saturday. About 20 miles out, heard a big rattle under the hood and car and pulled over to see what happened. Turned out the fan threw a blade that cracked and came off. And shear luck, no damage to the Brassworks brass rad or the hood. Removed the fan and ran the rest of the day with nothing. Result, no boiling, no spitting, not even a gurgle when shut off. And a good temperature differential from top to bottom that you could feel with your hand.

Combination, block and head boiled during the engine rebuild. Brassworks round tube factory style core. About 500-600 miles running so far.

I'm a fan of the original round tube core design. Thermosyphon works on a low pressure differential and round tubes have a lower flow friction than the flat tubes and are a good match for thermosyphon systems. Yesterday supported that choice.

Something to think about.

[TXGOAT2]

Interesting point... and probably valid. At best, the thermosyphon circulating pressure is very low, and a clean radiator is a must.
The flat tube dissipates heat into the air better, all else being equal, but the round tube would probably flow better, all else being equal. However, proper design could make either configuration perform well. The flat tube makes the tube itself into a sort of fin, and it gets a lot of tube surface into contact with the fins.

[TXGOAT2]

I ran my car today with no fan belt, but the fan still installed. No problem with heat in 93 to 96 F temperatures and speeds up to 47 MPH. Belt-less cooling would be better with the fan removed entirely. Green antifreeze may have a surfactant effect which could improve flow through the radiator at low pressure differentials.(I have a Berg's flat tube radiator)