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