Tractor overheats when mowing. No dealer actions fix it. Any ideas?

[aczlan]

OK, but if the thermostat went bad, and was removed to fix the problem, the engine should run on the cool side and not overheat.

Since it is/was overheating without the thermostat in place there is another issue.

Thermostats are used to raise the engine temperature to a desired level as quickly as possible. Not to enhance cooling.

That depends on how coolant flow is set up, coolant will always take the easiest path available to it, generally speaking there is a tee after the water pump with one side of the tee going to the head and the other side of the tee going through the thermostat and to the radiator.
if the path through the radiator is less restrictive than the path through the head, (without a thermostat in place), the majority of the flow will go through the radiator rather than through the head and so the head will not get enough flow through its to cool properly.
There will be flow through the radiator and the water pump, but not through the engine itself.
The restrictor or "racers washer" that was mentioned earlier is just a disc with a hole through the middle of it to restrict flow going to the radiator and force more of the flow to go through the head.

Aaron Z

 

[Henro]

Do you run any of yours engines without thermostat?

No. But they do not have issues.

And I would only do it for troubleshooting purposes.

 

[Henro]

That depends on how coolant flow is set up, coolant will always take the easiest path available to it, generally speaking there is a tee after the water pump with one side of the tee going to the head and the other side of the tee going through the thermostat and to the radiator.
if the path through the radiator is less restrictive than the path through the head, (without a thermostat in place), the majority of the flow will go through the radiator rather than through the head and so the head will not get enough flow through its to cool properly.
There will be flow through the radiator and the water pump, but not through the engine itself.
The restrictor or "racers washer" that was mentioned earlier is just a disc with a hole through the middle of it to restrict flow going to the radiator and force more of the flow to go through the head.

Aaron Z

Aaron,

That is interesting and could be correct.

I think the bottom line is there is a system that is likely properly designed, but develops a problem where it overheats.

A thermostat is there to get the operating temperature up to the desired point quickly and maintain there.

If the tractor overheats something is wrong.

If the thermostat is removed, it will take longer for the engine to reach desired operating temperature, a d may never get there on cool days.

But if the thermostat is removed for test purposes, and the tractor still over heats, there is an issue seperatefrom the thermostat. Blocked radiator? Collapsed hose? Whatever.

Point is the root cause needs to be identified.

There is no argument that if flow through the radiator is restricted, the engine will run hotter, and heat transfer at the radiator will increase. BUT since flow has decrease through the radiator, the net result is the engine will run hotter, not cooler.

I am starting to lose sight of why we are even talking about this...

 

[3gunr]

I started brushhoging a ten acre field yesterday that was about 3 to 4 ft tall ragweed and grass the tractor never got hot but after an hour or so i stopped and lifted the hood the oil cooler and radiater were caked with yellow pollen. took 20 minutes to blow it all out.

 

[Cat_Driver]

Guys even if the OP walks away from a good thread keep it going as other (LIKE ME) are here to gather information / solutions for similar issues.
Just because the OP is long gone shouldn't prevent good conversation on the issue to help other years down the road.

So what I'm saying IT DOES MATTER that we keep tossing out solution for others even if the OP is long gone.

 

[randyjs]

I had a '64 Corvette that ovheated without a thermostat, I figured the coolant was passing thru so fast that it wouldn't loose the heat.

 

[rademamj1]

I had a '64 Corvette that ovheated without a thermostat, I figured the coolant was passing thru so fast that it wouldn't loose the heat.

Just my thoughts. The coolant passes thru the radiator, from top of the radiator downward to the bottom of the radiator by gravity. Whether a thermostat is present or not, will not change the rate fluid drains downward inside the radiator. In fact, I cannot see anyway to over heat an engine without a thermostat unless the radiator cores are plugged, typically with scale deposits.

If anything occurs in a tractor without a thermostat, its going to be the coolant will stay much colder than normal, and not allow the engine to reach the optimum performance temperature. The onboard computer senses this colder engine and runs an over rich fuel mixture, which is going to increase fuel consumption and probably overtime leads to shorter regen periods and potential DPF emission problems. So removal of the thermostat should mainly be done to troubleshoot the cooling system, to determine if indeed its a thermostat or radiator core issue.

 

[LouNY]

Just my thoughts. The coolant passes thru the radiator, from top of the radiator downward to the bottom of the radiator by gravity. Whether a thermostat is present or not, will not change the rate fluid drains downward inside the radiator. In fact, I cannot see anyway to over heat an engine without a thermostat unless the radiator cores are plugged, typically with scale deposits.

If anything occurs in a tractor without a thermostat, its going to be the coolant will stay much colder than normal, and not allow the engine to reach the optimum performance temperature. The onboard computer senses this colder engine and runs an over rich fuel mixture, which is going to increase fuel consumption and probably overtime leads to shorter regen periods and potential DPF emission problems. So removal of the thermostat should mainly be done to troubleshoot the cooling system, to determine if indeed its a thermostat or radiator core issue.

Your water pump provides the motive force for all the coolant flow in your tractor,
the exception being some of the older lower hp ones that used a thermosyphon and the old hit and miss engines.
I did see a 1086 one night that ran in sub zero temperature and didn't over heat running a generator,
I wouldn't recommend it being done.

 

[pmsmechanic]

Just my thoughts. The coolant passes thru the radiator, from top of the radiator downward to the bottom of the radiator by gravity. Whether a thermostat is present or not, will not change the rate fluid drains downward inside the radiator. In fact, I cannot see anyway to over heat an engine without a thermostat unless the radiator cores are plugged, typically with scale deposits.

Just so you know the coolant comes out of the water pump into the bottom of the radiator, flows up through the radiator and then through the thermostat housing back into the engine. It does not flow by gravity. In a thermo siphon system it flows up due to hot coolant having a different density than cold coolant. In a water pump system it flows up because the water pump is pushing it up.

One of the purposes of a thermostat is to slow the flow of the water through the radiator so that the radiator has time to remove the heat out of the water. That's why race cars without a thermostat install a flow restriction in place of the thermostat.

I hope you don't feel like I'm picking on just your post. There has been so much misinformation posted in this thread that I couldn't keep quiet any longer.

 

[randyjs]

Just so you know the coolant comes out of the water pump into the bottom of the radiator, flows up through the radiator and then through the thermostat housing back into the engine. It does not flow by gravity. In a thermo siphon system it flows up due to hot coolant having a different density than cold coolant. In a water pump system it flows up because the water pump is pushing it up.

One of the purposes of a thermostat is to slow the flow of the water through the radiator so that the radiator has time to remove the heat out of the water. That's why race cars without a thermostat install a flow restriction in place of the thermostat.

I hope you don't feel like I'm picking on just your post. There has been so much misinformation posted in this thread that I couldn't keep quiet any longer.

I have to disagree with this, every vehicle I can recall the water goes into the water pump through the engine out the thermostat housing then out the top hose to the radiator. If it entered through the thermostat you would overheat when you were a quart low on coolant because it couldn't flow to supply the pump.