I good pal of mine was chiding me gently last Saturday for using anti-freeze/coolant in my radiator. He mentioned that this sort of a solution raised the boiling point and that meant the the thermo syphon would not work until the motor got too hot. He uses nothing but water soluble oil.
I thought that the anti-freeze/coolant would be good for several reasons.
1. It would protect from corrosion with the AL Z head.
2. The coolant would more readily remove heat than the oily liquid would.
3. The rise in boiling point would keep the thermo syphon working longer before it did boil.
My assumption is that heat drove the thermo syphon and that it would work with any difference in temperature. I believe my buddy thought that the bubbles of steam drove the system. In any case it occurred to me that I really didn't know which assumption was correct.
I have nothing agin the water soluble oil, I use it in the 20s Hudsons & in the'39 Cadillac as waterpump lube. It just seems to me that the Flivver (with no water pump) would like coolant better.
You pal is incorrect if he thinks bubbles of steam make the water circulate. I run 1 gallon of antifreeze and top off with water and thermo siphon works just fine in my cars.
He didn't actually SAY that the steam bubbles drove the system, I inferred it from his statement. He is a very knowledgeable T guy but as most of us are has very strongly held opinions.
Great to hear you are not having cooling system troubles.
Thermo-syphon works because heat rises.
(I cannot explain why it works in OZ)
Other posts pontificate on the heat transfer capabilities of various additives (anti-freeze).
Put "antifreeze MTFCA" (without the quotes) in your Google search box and you can read numerous theories....among the posts is this one:
as water heats it expands and weighs less so it goes to the top of the radiator, just like your water heater as the water trickles down through the radiator it gets cooler and heavier so it goes to the bottom, it is a constant cycle of expansion and contraction that makes it work.
Technically it is density that drives the thermosyphon. And density is inversely proportional to temperature. As heat goes up, density goes down. So the water heats up in the block and rises to the top water outlet. This draws in cooler water from the bottom of the radiator to replace it, which draws the hot water from the top radiator tank downward through the fins.
The question of whether antifreeze would help or hurt would depend upon what it's density to temperature graph looks like (along with its ability to shed heat in the fins).
Thermo-Siphon just means that hot liquids rise and cool liquids sink. It doesn't matter what the liquid is. This phenomenon happens in the bowels of the earth all the time --- hot magma rises from the depths of Hell, gets cooled near the surface of the earth and sinks back into the depths. Just like in a Model T.
Using antifreeze will not stop the thermo-siphon effect. Any fluid will work. The only thing which might not be good is if you use too viscous of a fluid which would slow down the fluid motion. But conventional antifreeze isn't even close to that. Honey might be too thick. Don't use honey in your Model T.
Actually antifreeze which boils at a higher temperature might even work better since the uniform fluid motion will continue longer than if the engine is percolating like a coffee pot. Has anyone tried it both ways and can say which is better --- antifreeeze or plain water?
or too much soluble oil coating the inside of the block and radiator reducing the heat exchange between the water and engine/radiator.
Does soluble oil have a greater affinity for the water or for metal?
Rick Bob and Scott all have it correct that heat makes the water (or other medium) expand and weigh less therefor being displaced upward by the heavier water from the radiator. The radiator conversely cools the water and the water contracts making it heavier for the same volume.
The difference in a cooling system that contains ethylene glycol is that there is much less water in the mixture. It is the water that carries the heat. Ethylene glycol does little to transport the heat away from the engine and to the radiator.
You will read on the container to not use large percentages of anti-freeze with little water.
Ponder this: when cars started using ethylene glycol from the factory the water pumps were made larger with larger hoses etc. to circulate twice as much coolant because the new coolant carried only half as much heat per volume as water did.
Thus the engine heat of a Model T will be carried away better with plain water ( or with soluble oil added for corrosion protection) than with anti-freeze.
I have used Evans coolant on a race car and it needs a pump. The density it unchanged by the temperature so themosyphon does not work with that coolant.
I am not sure about modern antifreeze liquids, my recommendation if you use antifreeze is to us a water pump.
If you use water, the themosyphon definitely works but it runs very lose to boiling point, especially at higher altitudes!
We've all heard all our lives that "heat rises", and we all just kinda take it for granted and assume it's some magical phenomenon that we never question, but never really understand either. The fact is, heat doesn't rise per se. Cold falls. It's gravity. That's all it is. Gravity. You cool a liquid and it becomes more dense. Gravity takes hold of it and pulls it down. The only reason the warmer liquid rises is because the cooler liquid is being pulled down by gravity and displacing it. It has to go somewhere and "Up" is the only place for it to go. Same thing happens with gasses, too. Hot air wouldn't rise unless there was cooler air falling due to gravity and forcing it to come up.
If there are any steam bubbles in the system, it's too hot.
Geez, I've put antifreeze in every one of my Farmalls and all three Model T's for years. None of the tractors or Model T's had water pumps. If they had them when I got them I took the water pumps off and threw them over in the corner where they belong. All of them ran very cool and efficiently. Thermo-siphoning works very well with antifreeze coolant. And as explained it works so well because hot liquid expands and rises while cold water condenses and sinks. Most thermo-siphon systems run cool enough without a water pump and in many cases a fan and fan belt aren't necessary.
The hot water rises, but don't forget the layout. The design of the head and piping allows it to rise to the top of the radiator. If the top hose was flat, or even pointed down to the radiator it would not work, at least not work near as well.
The old heating systems in houses worked the same way. Furnace was in the basement, near the center of the house with a big register for the heat to come out. Around the outside of the house were floor registers with rather large pipes leading back to the furnace. Hot air rose in the middle of the house and flowed back to the furnace via the floor registers at the outside.
Just a quick comment about antifreeze and pumps - with the mix I use of about 1/3 antifreeze and 2/3 water, my cars run nice and cool without any water pump. True for my 26 Coupe with stock or Z head and a round tube radiator and for my Fronty powered speedster. Both radiators are in excellent condition. No heating problems even with temps in the high 90's. If you have an overheating problem, it's probably something other than antifreeze.
Right on Walt. I normally run a 50/50 mix. This is the mix that works best for me with my T's sitting out in -30 degree F winter weather. Any less mixture creates a risk for freezing and cracking the block and/or radiator.
I'm with Walt on this subject also - I use 1 gal. antifreeze to 2 gals. water.
Well that's because of that tropical climate you live in.
Compared to the rest of the country ! We've been setting record "highs" in the Pacific Northwest the last couple days - went razor clam digging yesterday on the Pacific Ocean at Grayland in t-shirts - 62 degrees !
Not really "off topic" as these clams have a "syphon" to jet out the water & sand !
Dang, Steve, that's one of my favorite foods! Too bad I can't eat anymore.
Do you use guns or cannons?
Of all places, the Shilo Inn restaurant at PDX was one of the few I found in the PNW that had razor clams. I tried to eat there at every chance.
Well isn't there some kind of apparatus that's used to "suck" them out of the sand?
It's true that antifreeze has a lower thermal conductivity than pure water. From the standpoint of the ability to pick up heat, water is superior. But there are a lot of variables to consider in the whole system: optimal engine block temperature, optimal heat drop across the radiator, ambient temp, ambient humidity, fan speed, fan efficiency, vehicle speed, resistance to coolant flow in the block, etc. etc.
In the end, what's best is whatever works for you. And keep in mind that overheating can be affected by fuel mixture issues as well.
The one thing that does seem universally a good idea for improving heat transfer is water wetter.
My house was built the same year as my T - 1924. I have a large boiler in the basement and a radiator in every room. Originally coal-fired, it was converted to oil at some point. The water in the house circulates just like the water in the T. The pipes get hot to the touch, but the water doesn't boil. Even without the boiling, it moves up and down the pipes just fine.
So stick with me here: the heat makes the water rise and go upwards, right? That means in Australia all of the Model T's thermo-syphon action runs backwards! Up through the radiator and then down through the block. Since the water is pushed through the radiator it ends up working either way. Pretty crazy. =)
I second Mike's opinions. Except I run an even "stiffer" mix of antifreeze in my car adjusted to -47. Yeah, it can get darn cold around here. My problem was that the car ran so cold in all kinds of weather that I had to put a 160 degree thermostat in the system just so it would hit operating temp on the motometer. Even then it only ever hits the bottom of the circle on a warm summer day. I might need to put on water pump just to make it run a little hotter (just kidding!).
I use a gun (long tube) and my wife still digs with a short blade shovel - easier to "feel" the size of the clam before withdrawing it.
Limit is 15 clams no matter of condition (fragile shells) or size.
So Paul, now you know what drives thermo-syphon AND how to harvest razor clams. I'll bet that was more than you bargained for. I'd call that a good day.
Here's my experience. For many years I had Model A's and used California tap water in them and they got full of rust and the radiators needed to be cleaned from time to time. Then I tried "rust inhibitor" It helped some. I never used anti-freeze, because it rarely gets cold enough to freeze a radiator here. On those rare occasions when the weather bureau predicted freezing, I would drain the radiator. Did this with my other cars as well, and all had to have radiators cleaned every few years.
Then someone told me, probably through the club or on the forum to use the green antifreeze. I have been using it in all my T's and have not had radiator problems. I also use distilled water with the antifreeze, not tap water. I have gone over 20 years without radiator troubles. Just change the antifreeze every few years. It also does less steaming with loss of coolant. The thermo-syphon has been explained very well above.
This is what I do when I remove the radiator, head or hoses. If the antifreeze is fresh, I catch it and re-use it. If it has been used for a couple years or more, I discard it. After I re-assemble the car, I fill with tap water and warm up the engine. I check for leaks, and fix all leaks first. When I get the leaks fixed, I drain the tap water completely, and after it cools off, fill with 50-50 antifreeze and distilled water. If I need to add water from time to time, I use distilled water.
Dave said it right - Heat rises and cold settles downward.
The simple explanation is that hot water expands and thus has less density.
Then the lower density water rises to the top as the colder heavier water sinks to the bottom.
The motor heats the water and it flows upwards into the radiator where it cools and settles to the bottom where it is returned to the motor.
Antifreeze or any other additive may change the temperature but the liquid still expands when heated and contracts when cooled
As usual with Model T folk, we seem to have some disagreement on this subject. To complicate matters further, some anti-freeze/coolant mixtures advertise that they cool BETTER than water. Those are the ones I seek here in sun bleached SoCal where freezing is only something we see only on the TV news.
I have a Motometer, one of the chrome plated repop jobs and have installed it on a couple of drives. The red reads right at the line just below the circle no matter how long the drive was. It seems to rise there and stay. I'm not sure what would happen if it ever got cold. Saturday the temps were in the high 80s & low 90s and the car never seemed to get hot. I had the motometer with me but for some reason it decided to tighten fore & aft rather than athwartship so I left it in the trunk.
I seems that everyone has discounted the steam bubbles as a part of the thremosyphon process. I have found that if the engine temperature gets to boiling, around 200 degrees around here, that the coolant can flash to steam, this bubble rises quickly up the hose to the radiator, and increases the coolant flow, working as a secondary pump if the engine is creating heat faster than the temperature difference will do it.
Gustaf, I think you have distilled the thoughts my pal had. Model Ts often seem to bubble & steam a bit and even after the motor is switched off the ear can detect boiling sounds in the motor. I have not yet heard my own car do this but have often heard other Flivvers gurgling away after a run.
Probably the steam bubbles just helps a process that was already going on.
After I swallow too many clams soaked in butter my stomach tends to gurgle. too. No bubbles, thankfully. Guess the stomach flap (lower esophageal sphincter) acts like a thermostat in a T and keeps things under control.
(Yes, cabin fever is settling in here!)
Geez Dave, I've drank cheap beer and have had my lower sphincter gurgle and bubble at the same time. Then it doesn't take long and everything heats up. The worst is the corrosive overflow that...
The reason the car bubbles after you turn it off is that the car is no longer moving into the wind, and the fan is no longer turning, so the cooling process in the radiator slows down, causing a temporary rise in engine temperature. It usually only lasts a few seconds unless the engine was already overheated when it was turned off.
"...causing a temporary rise in engine temperature."
It's not a temporary rise in engine temperature. It's a temporary rise in coolant temperature. The thermosyphon process ceases and coolant stays in the block long enough to absorb enough energy to bring it to a boil. It is therefore a DROP in engine temperature, as heat is transferred from the block to the coolant, eventually causing it to briefly boil.
Gustaf & Paul,
Steam bubbles are not part of thermosyphon process. If anything they impede it by creating turbulent flow. Consider also, if big bubbles of air are partially filling the head & radiator hoses, that is volume NOT occupied by coolant. Coolant transfers heat, not air bubbles, (o.k. steam bubbles).
Check the layout of the water passages and the location of the water connections to the engine. The cooled water comes in at the mid point between cylinder two and three. The water absorbs heat and gets pushed up when the new cooled water in the radiator is getting heavier. The exit from the head is at the front and the main flow of water goes the shortest way from the inlet in the block to the water outlet in the head. To cool the rear cylinders the water needs to make a detour - why would it? I think the flow of water is lower in the rear of the engine and the coolant there may reach boiling temperature momentarily, causing the barfing and gurgling sounds we hear from a model T when it's just been stopped.
Maybe one of the reasons for cold running in #1 cylinder (resulting in a sooted spark plug) is the layout of the cooling system that cools the front cylinder almost too good while the rear cylinders runs hotter?
Some engines like old mopar 6 cyl flatheads had sheet metal parts inside the water channels directing the coolant flow. Maybe a sheet metal diverter in the water inlet of a model T engine could direct the flow more to the rear for a more even engine temperature?
Jerry, what stops thermosyphon when the engine stops?
Retarded timing will cause thermobarf.
The loss of the cooling fan or forward movement of the auto, thus no air flow over the cooling fins of the radiator.
I'm far from sure the thermo syphon stops when the motor does. I have noticed that the engine cools rapidly (compared to other cars) after the motor stops.
The thermosyphon circulation system will work just as well with the engine running as not as long as there is a temperature difference and there is some air flow through the radiator. The more temperature difference and more air flow through the radiator the better it works.
Actually some bubbles of steam, as long as the volume of steam does not become a problem, is a very efficient method to transfer heat. It takes one BTU to raise one pound of water one degree Fahrenheit. However to change one pound of water from a liquid to steam it takes 970 BTU/lb. In an engine the heat to change water to steam comes from the engine and then when the steam is transferred to the radiator where is condenses it gives up the same 970 BTU/lb.
Based on weight of material transferred from the engine to the radiator, the transfer of heat with steam rather then water is 970 times more efficient then plain water.
Not only does the transfer of heat because of the phase change of water to steam and back work, also the weight of water with bubbles of steam in it weighs much less then plain water and this weight change increases the circulation caused by the thermosyphon effect.
The bottom line is that the cooling system becomes much more efficient with a little bit of steam. That is the reason an engine will come up to the boiling point and them continue to run at that temperature for an extended time without getting hotter.
I agree with Jim,
My car tends to run hot enough to vent a bit of steam after a long drive on a hot day, even before it is shut down. The steam bubbles in the head or outlet pipe can in no way impede cooling as the bubbles will be at the top of the head, and coolant will be at the bottom of the cavity in the head where the heat is, as those bubbles move up the outlet hose, they are going to cause movement, much like the air pumps that we have used to pump water from 200 feet down, just by pumping air into a special coupling, water can be raised with nothing but bubbles.
If your car makes steam, there is no doubt it will flow upwards into the radiator. But I am still of the opinion that if your car gets hot enough to make steam, it is because the cooling system is not doing it's job.
I used to get the gurgling after shut down, but not since I put a new radiator on it (Them).
O.K. I can see your point about the steam question.
However, you state, "That is the reason an engine will come up to the boiling point and then continue to run at that temperature for an extended time without getting hotter." Well, unless you're now making superheated steam wouldn't that be normal, since water can't exceed 212F without changing phase? So, as long as you have water in some quantity, it can't go over 212.
That is true, Jerry, but I don't think it would be abnormal for a car to reach some 'operating temperature' even if that temperature was something below the boiling point. The thermosyphon system is kinda self regulating. If the temperature tries to get above the 'operating temperature' if flows faster and cools more and brings itself back down to 'operating temperature'. So I can see it staying within a fairly narrow temperature band.
In my 24 touring Distilled water Or distilled water & water soluble oil run at 190 deg. +-
50/50 distilled water antifreeze run 210 deg.+-
Temperature sensor in water outlet.
Great to hear about your results from experience, Dean
Did you notice any difference in performance like gas mileage when running with the different coolants?
(Adding to my post aimed at Dean Y)
..And 210 F+/- is very close to boiling.. Did it boil much?
You're a man with many heads - have you noticed any difference in boiling tendencies between different heads?
I would suspect higher compression would get more useful work out of the gas and less excess heat to cool off + better mileage, but you'll know the real data
Dean, what does the temp run on a cool day?
You are correct, as long as there is water you are pretty much limited to 212°. That is the way hit and miss engines work, just keep water in them and they run at 212°.
Run a light mix (less than 50 percent) of Prestone and distilled water.
Temp sensor in water outlet. High compression head, coils on magneto, Champion X plugs.
At road speed stays constant 180. Can bump 200 on hard run of 45+ or long haul up a hill. When throttled down, back to road speed, within one minute or a half, the temp drops back to 180.
Normal reading on tour, easy cruise @ 30-35
Warm summer day run on fast highway...
the type of head does not seem to make any difference. The age of the radiator does when my radiator was new I ran at 160 Deg. I now run at 190. The right gage is oil temperature it usually runs 10 deg. lower than the coolant. In this photo I was pushing the heck out of it and my oil level was above the top petcock. When my oil temperature is more than 10 deg. lower than the coolant it is time to add oil.