Thermo Siphon

[atk_man]

Does anybody have any idea how the thermo siphon cooling system works? I do my best to keep the rad full and clean. I do see the odd drip coming out of the overflow every now and then. I don't necessarily want to wait until it overheats to discover any problems. How often should it be flushed? How do you flush it? Is it as reliable as a water pump?

Thanks.

 

[RobertN]

As the water heats, it rises. After is rises up to the radiator, it cools and falls down. It creates a cycles that works really well. My old Farmall has that system; it could plow all day in hot weather without a problem.

It's important if you mix anti freeze in with the water, that it is well mixed. Otherwise the unmixed vs mixed will have different specific gravities, and will not flow properly.

If it is really down, then the best thing is to completely drain it, mix the water/antifreeze, and then fill all the way up.

From my Farmall A service book:
"Cooling water is circulated through the engine block, cylinder head, and radiator by thermosiphon method. As the engine warms up the water is heated, expands,, and circulates down through the radiator where the water is cooled before again circulating through the engine."

They do note that to clean the system you drain it, and then fill with a solution of "two pounds ordinary washing soda" with water. Run it till hot, then drain and refill. However, this is for a 1941 year tractor

 

[Worksmart]

Henry - Beside Robert's Farmall A, I have 2 of the over 300,000 Farmall/International Cubs made between '47 and '79. They also used the thermo-siphon system. So I guess it was an acceptable method of cooling. The only change I'm aware was made over the 32 years was from a 0lb cap to a 7lb cap. That only change raised the boiling point and had nothing to do with the theory of the thermo-siphon system.

Like RobertN mentioned, just make sure you pre-mix outside of the tractor. No water pump=no mix. Chuck

 

[Bird]

<font color=blue>I do my best to keep the rad full and clean. I do see the odd drip coming out of the overflow every now and then</font color=blue>

I'll assume your tractor has no "coolant recovery jug" since my B7100 did not. Therefore, if the radiator is full, as the coolant warms and expands, it pushes some out the overflow tube, then as it cools and contracts, it will be down a little bit if you check it cold. In other words, there's no way you can keep it full to the top, it isn't necessary for it to be full to the top, and it sounds as if your situation is normal.

Personally, I was concerned about the lack of a water pump, lack of a temperature gauge, and lack of a coolant recovery jug when I had a B7100, and I considered adding a coolant recovery jug so it would stay full on the theory that not letting any air into the radiator would reduce the chances of rust forming. However, a Kubota factory service rep told me that IF it started to overheat, I would hear it "whistling" and it never did that. I didn't think to ask him at the time, but wondered later if adding a coolant recovery jug might prevent that audible warning in the event of overheating, so I never did any modifications at all to it and never had a problem.

 

[Egon]

Bird:
I have had the "Whistle" blow two or three times on my 7100. Once was when the dynamo siezed and broke the fan belt, the others times the rads became plugged with poplar fuzz. The overflow from the rad ends with the whistle.

It's quite audible and visible as a cloud of steam appears at the right front wheel.

Egon

 

[Bird]

Egon, I'm glad to know the "whistle" works, but also glad mine never whistled./w3tcompact/icons/laugh.gif

 

[Egon]

Bird:
Your maintenance schedule is better than mine.

Egon