Thermostat siphon systems

Mark Poss · Apr 11, 2017

Started a couple of tractors today that don't have water pumps and they were running hot after a short while. Can the water and antifreeze separate during the winter causing a block and keeping the system from circulating? thanks Mark

kcm.MN · Apr 11, 2017

Never heard of anti-freeze and water separating. As far as I know (which isn't much), the only thing that can cause something like that is a malfunctioning thermostat. These 2 tractors you mention "do" have thermostats, don't they?

Mark Poss · Apr 11, 2017

No they don't. I meant to type in thermo siphon systems and it. came up thermostat. One tractor is a 28 regular the other a35 John Deere b

robgIN · Apr 11, 2017

Define running hot , were they boiling over , water coming out overflow ? They have to heat up to function, the coolant will not circulate until there is enough temperature differential for the process to start, the hotter water rises up until it enters the radiator where it is cooled and the cooler liquid sinks down to be drawn back into the bottom of the engine to start the process all over again, pretty much the same as ocean currents. Generally speaking if a thermo syphon system is not pushing coolant out the overflow or boiling over , it is working properly . It does not circulate fast like a pump system , that's why they have a larger volume of coolant capacity vs a water pump system of similar size engine.

Mark Poss · Apr 11, 2017

The radiator on my regular was steaming after running for five minutes

Russ from MN · Apr 11, 2017

I didn't think a tractor with a thermosiphon cooling system had a thermostat, shouldn't need one.

OldFarmall450 · Apr 11, 2017

A thermo syphon system (aka evaporative cooling system) runs better when using straight water. The water has to reach boiling or vey near it for the steam to rise up the pipe to the top of the radiator. Then the cooler air from the fan converts it back to water and so it goes.
We farmed with a JD A, and never used anything but well water in it. Had to drain it in winter, but no problems boiling over. We didn't even have a cap, used a rag and a tomato sauce can. It would run away with a 2 bottom plow, but the 4x14 had to cut shallow and in low gear or it would boil over.

Janicholson · Apr 11, 2017

Sorry to need to deny Old Farmall 450. The system is not evaporative at all. The coolant does not evaporate, it circulates from convection currents caused by hot water being less dense than colder water. The hot engine water flows into the radiator as the colder radiator water drops through the hoses into the bottom of the engine. They work well when clean. The tractor will warm up faster than one with a water pump, but they should not overheat.
The level of coolant (always use 50 50 mix, it does not separate or reduce coolant flow, it does prevent freezing, rust/corrosion, and is proper to use. The level of coolant in the system is about an inch above the top of the core in the radiator. Put a clean stick down the hole till it stops. pull it out one inch is perfect. Over filling as you would fill a modern car with a separate reservoir, is not correct. Jim

OldFarmall450 · Apr 12, 2017

Jim, no hurt feelings here. I thought the system worked like a moonshine still; the water turned to steam and moved up the pipe, then reached the fan where it cooled down, condensed, turned back to water. The old man we got the JD from said using antifreeze raised the boiling temp, which caused the motor to run hotter. It sounded good to me at the time, always accepted it as gospel.
I know it DID get hot quick, and stayed hot. Hot enough to run diesel in it and pull a plow.
I bow to your wisdom, as always.
ET

FBH44 · Apr 12, 2017

I don't think separation is possible, I think they go into solution. Otherwise the entire nation would be full of frozen-up-busted-up cooling systems, with the water separating out and freezing all the time.

D beatty · Apr 12, 2017

The old tractors thermosiphon systems used shutters to obtain the temperature you wanted. Permanent anti freeze will not separate but the old methanol anti freeze could freeze if you didn't keep track of it.

BarnyardEngineering · Apr 12, 2017

Cooling systems probably haven't been serviced in a while, right? It wouldn't hurt to drain, flush, fill with white vinegar, run a while, drain again, flush again, and refill with fresh 50/50 mix.

I worked on a Cub a couple years ago that the lower radiator tank was full of slime.

tn terry t · Apr 12, 2017

(quoted from post at 03:15:47 04/12/17) The old tractors thermosiphon systems used shutters to obtain the temperature you wanted. Permanent anti freeze will not separate but the old methanol anti freeze could freeze if you didn't keep track of it.

nope your thinking of Distillate tractors thermosiphon sure don't need help heating up you ever see a cub with shutters on it?

D beatty · Apr 12, 2017

I have one of the last Farmall Bs made and it is gas and has shutters. The shutters are used in winter to get and keep engine at running
temp. Thermosiphon systems have a tendency to run cold cold in winter and shutters are use to maintain engine temp.

robgIN · Apr 12, 2017

you may have plugged radiator , or enough restriction somewhere that it is not circulating. They have a tendency to accumulate a lot of sediment over time . You could have a head gasket issue or a cracked head also . Might be time to take the lower radiator fitting off and the elbow on the side of the block off and see how much crud you have in there. Start with the easy stuff first. I know a couple of my F-20s have had a lot of crud built up in the block and bottom of radiator.

F-Dean · Apr 13, 2017

If the radiator leaked or gasket was not tight or the gasket was a little off, the Regulars and F-20s would loose water. Solution, carry a gallon-can so you could refill with water from the creek. This is the most common way they got clogged with dirt from the muddy water.

SMX7090 · Mar 12, 2018

Hello,

I'm writing from Belgium. I am rebuilding a 1948 Farmall Super A C113 without waterpump. I have no experience with thermosiphons and I am facing a problem. After having checked and flushed both the engine and radiator I started the engine. It runs perfectly ! But... it tends to overheat, well, in my opinion... After a 5 minute run, water starts gurgling through the inlet on the radiator. Measuring the water temperature : (90 degC - 195degF) Measuring cylinder head temperature (with IR pistol) : 110degC (=230degF). Water seems to boil out of the radiator instead of circulating properly. As I have no experience with thermosiphon, I don't know if it is normal or not. In a waterpumped engine, water tends to be still... Here it seems to be boiling. Then I stop the engine, not wanting to harm it.

Can someone help me ?

Thank you

Serge Marcoux

BarnyardEngineering · Mar 13, 2018

First thing, 90C is not boiling. If you are using a proper 50/50 antifreeze/water mix, the boiling point is 106C. You have a long way to go.

Second thing, if you are filling the radiator to the top, you are overfilling it. The coolant expands, and has nowhere to go, so it will "boil" out the top. Only fill the radiator to just above the top of the fins to allow for some expansion.

Third thing, there will be air in the system if you just recently filled it. The air will come out in bubbles, making it look like the system is "boiling" when it is not.

Fourth thing, the thermosiphon systems will run a little bit hotter than a system with a thermostat and water pump.

Do not panic right away. Let the engine run a little longer to see if things stabilize.

There may be other factors causing your engine to run hotter than normal, such as timing and fuel mixture.

SMX7090 · Mar 13, 2018

Thanks for your quick answer ;-).

1st : I am using water and will replace it with proper coolant mix.

2nd : Fuel used is Euro gasoline 95RON. Don't know if I can use another fuel maybe 98RON...

3rd : Timing "should" be correct regarding specs in the manual (set at 8deg). Will try to vary it.

4th : What is the highest temperature of the cylinder head (measured externally with an IR pistol) before having real overheat issues ?

Thanks again. Will give you feedback.

Serge Marcoux (Belgian fries eater ;-)

oldhammerhead · Mar 14, 2018

(quoted from post at 20:59:20 04/11/17) Started a couple of tractors today that don't have water pumps and they were running hot after a short while. Can the water and antifreeze separate during the winter causing a block and keeping the system from circulating? thanks Mark

ark check overflow tube for blockage, My 10 20 had same issue.

Thermostat siphon systems

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