No thermostat?

[Laneman950]

I just read that tractors don't need thermostats. It said none of the overseas models have them, only U.S. models. I have a John Deere 950 with a diesel engine. If the thermostat is not necessary I would rather remove it. I've heard that on gasoline cars they are necessary for some reason.

 

[montejw]

I just read that tractors don't need thermostats. It said none of the overseas models have them, only U.S. models. I have a John Deere 950 with a diesel engine. If the thermostat is not necessary I would rather remove it. I've heard that on gasoline cars they are necessary for some reason.

Where'd you read that? Gas engines don't need a thermostat either, they just won't run optimally at cooler engine temperatures, just like a diesel won't. The engine temp needs to get up around 190*-200* to run most efficiently. If your's will do that without a thermostat, take it out. It'll also take longer for the engine to warm up, and it'll run hotter and cooler as the outside temperature is hotter or cooler.

And depending on how cool it runs and the humidity outside you could possibly have moisture problems inside the crankcase if it doesn't run hot enough to purge all of the moisture out of the crankcase.

Monte

 

[CATMAN]

About 4-5 years ago, I read a good article in the John Deere magazine "The Furrow", it says the oil become acidic between 100F to 160F. It mentioned about proper maintanence of the cooling system also. You need that oil temperature to be hot enough to burn off the moisture/condensation in the crankcase.

The rule of thumb is that when a diesel engine is under a hard load that the oil temperature is 20-40F hotter than the cooling system IF the engine uses a water-cooled oil cooler. I run diesel engines on a chassis dyno and with 190F thermostat and the engine under load with a good cooling system, you will see about 196F coolant temp and 220-225F oil temp. This is normal. Every diesel engine I have worked on, from 1961 John Deere to current CAT engines have/require a working thermostat.​

Without thermostats in engines that where designed for a thermostat, you will see overcooling under light load conditions, and then you will see overheating under heavy load conditions. A better term for a thermostat is the word, REGULATOR. A regulator has a set opening temp(say a 190F) and then after that is varies its opening clearance to either send coolant to the radiator OR back to the water pump(to cycle back thru the engine block again). Example: IF the regulator is 1/2 open(say at 198F), then 50% of the coolant goes to the radiator and the other 50% goes back to the water pump to be MIXED with the COOLED coolant coming from the bottom hose out of the radiator. Now, lets say it is really hot outside and you are working the engine really hard, the regulator would be wide open(206F) and that forces 100% of the coolant thru the radiator before it gets back to the water pump, then the cylinder block. I hope this helps you understand the need for a thermostat/regulator.

 

[Egon]

Some engines run on a thermosiphon principle that does not include a water pump.

Perhaps do some googling and all will become clear.

 

[skipmarcy]

Monte & Catman are both correct. Alot of uneducated people will remove a thermostat trying to fix a overheating problem and just cause themselves more grief. To clarify why an engine would actually overheat with a thermostat removed - at higher operating RPMs the water pump is circulating the coolant too fast for proper heat transfer, first the heat from the engine to the coolant, then the heat from the coolant to the radiator cores, it's not staying there long enough for the heat transfer to occur. Now if you have a radiator that's half clogged it might cut the flow enough to fool you into believing you've "fixed" the problem by removing the thermostat, but all you've done is mask the real rpoblem and it's going to bite you in the...

Running the engine too cool cause several different problems, especially in automotive with computerized systems. One critical problem it causes in any engine is "fuel quenching". This is when the cylinder walls stay too cool and some of the fuel condenses on the walls and isn't combusted. This fuel washes oil from the cylinder walls & rings - not too difficult to see what that can do. This fuel ends-up in the crankcase with your oil.

If it was designed to operate with a thermostat, it needs one in there, and of the proper temp.

 

[Laneman950]

Thanks for the replies- thermostat stays, albeit a new one, since I don't know how old the "old" one is.

 

[SPYDERLK]

Quote skipmarcy: To clarify why an engine would actually overheat with a thermostat removed - at higher operating RPMs the water pump is circulating the coolant too fast for proper heat transfer, first the heat from the engine to the coolant, then the heat from the coolant to the radiator cores, it's not staying there long enough for the heat transfer to occur.

I would search for another explanation to this phenomenon that is sometimes observed because, increased flow causes turbulence which, like stirring, transfers heat better. What is probably happening, where worse overheating is observed w/o the tstat, is boiling of the coolant in the pump suction line. This will happen if the radiator cannot pass the increased flow freely. Bubbles in the coolant are definitely a problem. Another possible contributing detriment in some cases is collapse of an unreinforced suction hose.
larry

 

[skipmarcy]

Quote skipmarcy: To clarify why an engine would actually overheat with a thermostat removed - at higher operating RPMs the water pump is circulating the coolant too fast for proper heat transfer, first the heat from the engine to the coolant, then the heat from the coolant to the radiator cores, it's not staying there long enough for the heat transfer to occur.

I would search for another explanation to this phenomenon that is sometimes observed because, increased flow causes turbulence which, like stirring, transfers heat better. What is probably happening, where worse overheating is observed w/o the tstat, is boiling of the coolant in the pump suction line. This will happen if the radiator cannot pass the increased flow freely. Bubbles in the coolant are definitely a problem. Another possible contributing detriment in some cases is collapse of an unreinforced suction hose.
larry

No, this is not my theory. This I learned at the GM training center in Tarrytown, N.Y. back in the early 70's during my apprenticeship with Cadillac. I have seen this occur in virtually all types of autos over the years. Back when thermostats weren't quite the quality they are nowadays and failures were more common, a true mechanic would know to remove the thermostat and gut it (cut the harp and remove the central components) and re-install the flange body to create a restriction in the flow, thus bringing the temp. gauge back down closer to normal until a new replacement could be installed.

 

[Keoke]

You boys are right on, a thermostat is actually a tuned orifice between the suction and pressure sides of the water pump. And it has three jobs, to keep engine temp in range, to slow coolant down so that it spends enough time in radiator to effectively transfer liquid heat to air and to slow water flow enough to prevent cavitation (air bubbles) on the suction side of pump.
When buying replacement stats make sure the full open hole is the same as the OEM stat.

cheers,

 

[MJPetersen]

It said none of the overseas models have them, only U.S. models.

No one addressed this aspect of the question. Is this part true? I ask because my 1510D start blowing warm air back from the radiator shortly after starting and I figured that the thermostat was stuck open, but I did not see any obvious place for it. The top hose connects directly to water pump without any obvious flange and thermostat housing. I have a 186 repair manual and the pics in there show a different outlet and an obvious thermostat housing.

Mike

 

[skipmarcy]

No one addressed this aspect of the question. Is this part true? I ask because my 1510D start blowing warm air back from the radiator shortly after starting and I figured that the thermostat was stuck open, but I did not see any obvious place for it. The top hose connects directly to water pump without any obvious flange and thermostat housing. I have a 186 repair manual and the pics in there show a different outlet and an obvious thermostat housing.

Mike

I can't understand what difference it would make where the tractor was used in the world as to leaving the thermo. out. Different temp. ranges yes, but not controlling engine temp. at all seems very foolish. I can't think of a reason why they would leave it out of the system.

 

[Soundguy]

Any chance your yanmar was thermosyphon?

i know the 1700 is.. and can accept the pump from a 2000 as a conversion...

Soundguy

No one addressed this aspect of the question. Is this part true? I ask because my 1510D start blowing warm air back from the radiator shortly after starting and I figured that the thermostat was stuck open, but I did not see any obvious place for it. The top hose connects directly to water pump without any obvious flange and thermostat housing. I have a 186 repair manual and the pics in there show a different outlet and an obvious thermostat housing.

Mike

 

[john_bud]

I just read that tractors don't need thermostats. It said none of the overseas models have them, only U.S. models. I have a John Deere 950 with a diesel engine. If the thermostat is not necessary I would rather remove it. I've heard that on gasoline cars they are necessary for some reason.

Yeah, and I just read on the internet that politicians don't need brains!

Well, I guess some internet rumors are true after all....


But you do need thermostats, especially on diesels to get them up to correct operating temperature for complete combustion. Hot diesel engines run more effieciently than cold or cool engines.


Gas engines are heated up so that the emissions control equipment can be tuned for consistent operations.

Naturally, there are 3001 other reasons why thermostats are needed in both gas and diesel engines! But, reasons to remove one? Hmmm , nope don't know any of those!

jb

 

[MJPetersen]

Any chance your yanmar was thermosyphon?

i know the 1700 is.. and can accept the pump from a 2000 as a conversion...

Soundguy

Nope that is DEFINITELY a water pump. But it is curious as the Hoye parts manual does not show a thermostat anywhere. Guess some rumors are right. I wonder how they planned on getting the thing to normal temp in the winter? cover the rad I suppose, but they you need a gauge so that you know when it is time to open it a bit.

Hoye has a sale on the pumps right now for $116.
Mike

 

[dynasim]

<to slow coolant down so that it spends enough time in radiator to effectively transfer liquid heat to air>

is not valid. The amount of heat removed by the air passing through the radiator is directly related to the temperature of the water in the radiator. If you slow down the flow in the radiator, you will decrease the temperature in the radiator, and you will remove less heat.

If GM taught this concept, they had poor engineers. I can believe that.

There may be reasons to keep constrictions (open thermostats) in the line. Primarily, the pump was designed with that restriction. The reason is just not this one.

Chris

 

[3RRL]

The amount of heat removed by the air passing through the radiator is directly related to the temperature of the water in the radiator.
Ok, I agree with that.

If you slow down the flow in the radiator, you will decrease the temperature in the radiator, ...
So slowing down the flow in the radiator decreases temperature in the radiator. Yes, I agree with that too, but why? It's because it has time to dissipate the heat more effectively. That is THE big reason to leave your diesel idle for several minutes before shutting down. Especially on turbo charged units.

... and you will remove less heat.
Because there is less heat to remove because of the above.

In otherwords, what you said was "not valid" (<to slow coolant down so that it spends enough time in radiator to effectively transfer liquid heat to air>) is indeed a valid statement IMHO.

 

[SPYDERLK]

Quote 3RRL: So slowing down the flow in the radiator decreases temperature in the radiator. Yes, I agree with that too, but why? It's because it has time to dissipate the heat more effectively. That is THE big reason to leave your diesel idle for several minutes before shutting down. Especially on turbo charged units. " "

So youre describing cooling less water more. This is not necessarily better than cooling more water less. Faster flow increases turbulence which aids heat transfer. Admittedly, the water would not cool quite as much during its quick pass thru the radiator but it would be passing thru more often and would more than make up for it. The "not enuf time to transfer heat effectively" is an attempt to explain what has been seen when removing thermostats and seeing a detriment. Its not a correct explanation because it does not obey physical laws governing heat flow. I suspect what really explains it is that bubbles form in the coolant under flow conditions that are caused when the thermostat is removed.

The reason for idling before shutdown is not as much related to this as it is to reducing the amount of heat being produced. It lets the hot spots cool gently while the cooling system and oil continues to distribute and remove the heat.
larry

 

[skipmarcy]

Quote 3RRL: So slowing down the flow in the radiator decreases temperature in the radiator. Yes, I agree with that too, but why? It's because it has time to dissipate the heat more effectively. That is THE big reason to leave your diesel idle for several minutes before shutting down. Especially on turbo charged units. " "

So youre describing cooling less water more. This is not necessarily better than cooling more water less. Faster flow increases turbulence which aids heat transfer. Admittedly, the water would not cool quite as much during its quick pass thru the radiator but it would be passing thru more often and would more than make up for it. The "not enuf time to transfer heat effectively" is an attempt to explain what has been seen when removing thermostats and seeing a detriment. Its not a correct explanation because it does not obey physical laws governing heat flow. I suspect what really explains it is that bubbles form in the coolant under flow conditions that are caused when the thermostat is removed.

The reason for idling before shutdown is not as much related to this as it is to reducing the amount of heat being produced. It lets the hot spots cool gently while the cooling system and oil continues to distribute and remove the heat.
larry

There is no air to form bubbles in a properly filled, closed cooling system. Heat transfer from the coolant to the metal surface of the tube in the radiator - the longer it stays in contact with this cooler surface, the more heat is transfered away from the coolant. Same thing with the heat transfer from the iron cylinder wall to the coolant. Pour a cup of water in a hot skillet for 5 seconds or for 15 seconds - which one will produce hotter water? It's pretty basic. In the case of removing a thermostat in an engine, some systems can handle it better than others, depending on alot of factors, but in most automotive engines you will definitely see some sort of increase in operating temp. at higher rpms, some to the point of overheating especially if the radiator isn't 100% clean or a soft lower hose trying to suck shut etc. etc. It's still a good idea to gut a bad thermostat as opposed to removing it completely to get you by until a replacement can be installed.

 

[Tom_Veatch]

"It said none of the overseas models have them, only U.S. models."
No one addressed this aspect of the question. Is this part true?

Mike

No, it is not true. The YM2220, which is definitely a Japanese rather than an U.S. model, does have a thermostat. Or at least the one I own does.

(And as other's have indicated, physics is no respector of national origin. Physical principles are the same regardless of the language printed on the warning decals.)

 

[Egon]

Lets consider boundary layers, rate of heat transfer for ambient conditions, laminar or turbulent fluid flow and its impact on rate of heat transfer to fluid mass per given unit of time!