Thermostats in Thermo Siphon Systems

The viagra tabs fact is, if you have an opinion it is going to be contrary to another man’s opinion.

There have been about four different people point out that there is a WEB SITE(s) that suggests having any kind of valve in the upper half of the thermo siphon loop is risky, and could cause problems if the valve sticks.

In the old days, this may have made more sense to me, an engine usually had an operator attending to the machine, he might be there to assure the engine warmed up, and was not run cold.

Fact is, any engine can benefit from a rapid warm up, and auto thermostats have been doing a great job for years. Engines that run cold burn excessive amounts of fuel, ring wear is accelerated, they form carbon deposits that can lead to burnt exhaust valves, and more! If you are worried about one sticking closed, ask for the safety thermostat, it’s a dollar or two more, but designed NOT to stick closed.

Closed thermo siphon loops accommodate antifreeze, anti rust compounds, and when a thermostat is added, the engine will run at a specific temperature and run more efficiently and live a longer life.  That’s why millions upon millions of engines use them, and it makes no difference if it’s a properly designed thermal siphon system or one that uses a pump. Of course we know, that pump will fail sooner or later, and I get reports of them going out more often than we’d like to hear about.

It’s all about risks and rewards, I’ll take the thermostat any day!

Check out the Utterpower thermostat housing.

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2 Responses to Thermostats in Thermo Siphon Systems

  1. david says:

    Wouldn’t a thermo siphon regulate itself? When the engine is cold there would be no heat difference around the system so there would be no flow. I imagine significant flow would not begin until the water in the engine was a least warm, then the hotter the engine gets the faster the circulation caused by the larger temperature difference. I imagine the same would happen in reverse if the engine was to go from high to light work load and so cooled down, slowing the water circulation. My question is how effective is this natural regulation? or how much better does a thermostat perform? or how big is the reward?

    • George B. says:


      This is a topic so large; many books have been written about it. If you have a six one, or any water cooled diesel engine, there are some experiments you can run yourself and become more confident in my Answer.

      When we start a diesel from dead cold, the combustion chamber is cold, there’s cold coolant on the other side of the cylinder liner. Combustion is poor at first, and the amount of fuel for a given amount of work is always higher than when the engine is up to temperature.

      Let me give you an example of my diesel pickup which has a very good onboard system for measuring fuel consumption. When I start the truck and head down the road, I see figures as low a 4 miles per gallon when cold, as it warms up, the fuel usage gets much better, typically 16 MPG or higher, but that first few miles I drive can be costly. It’s very similar to pouring water on a fire, you are robbing heat from the fire, and this fire is attempting to drive that piston down the bore and do some work for you.

      The cold metal and coolant literally quenches the combustion chamber, and cylinder and it is necessary to open up the fuel rack further to get the same power.
      A rapid warm up is assured with the thermostat, you want the engine to reach it’s operating temperature as soon as it reasonably can. The thermostat is not an on and off device, when the temperature is reached where it starts to open, it cracks open just a little, and if you study the amount of flow, it is very little at first.
      Without the thermostat, water circulates freely and the engine remains cold until we burn enough BTUs to heat all the coolant in the tank, radiator, block, whatever. IF that is even possible. A diesel that is lightly loaded may never be able to heat the coolant to a decent operating temperature if the ambient temperature is low, or active elements move the heat off.

      In a thermal siphon system without thermostat , you don’t need much heat to circulate the water. All you need is a temperature differential of a few degrees, water expands and is lighter even if it’s just a few degrees warmer than what’s below it.

      Indian farmers, use bleed water from water pumps to cool an engine, the smarter operator will adjust the water flow where it comes out of the engine not too far below boiling, since the engine is up against a steady load when pumping water, it is fairly easy to regulate this temperature, and if the pump doesn’t lose prime all is well. If the farmer runs water through the engine cold, fuel usage will be far greater, and engine wear will be severe.
      If you have a 6/1 with a generator, you have all you need to conduct your own experiment. Regulate the temperature around 200F and run a 2kw load for one hour.. measure the fuel usage.

      Now, disconnect your upper and lower cooling lines, and hook your garden hose to the lower port, let the water flow freely from the top cooling port and run the same 2kW load for an hour.. compare fuel used.

      Of course your second experiment is to see how long it takes to warm up a, engine using a cooling tank without a thermotstat, certainly, there are alot of small tanks at rallies that might heat up quicker, but they are not designed to work the engine, We are not interested in showing our engines here, we actually work them. Remember a diesel engine with no load doesn’t make much heat, engine wear could be 5 or more times greater because you are running it too cold.

      All the best,

      George B.

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