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

Reb954 · Sep 2, 2020

I would have to argue that too. Every engine I am familiar with, the coolant flows into the top of the radiator and out the bottom to the water pump. That is why the thermostat spring is on the engine side so the hot water will heat it causing it to open the thermostat which lets the coolant run to the top of the radiator. If the spring was on the cold side (radiator side) it would be slower to open causing more dramatic changes in temperature.

pmsmechanic · Sep 2, 2020

randyjs said:
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.

You are correct. I'm going to look at a few more engines though.

Egon · Sep 2, 2020

pmsmechanic said:
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.

Misinformation?

Pretty standard configuration.

pmsmechanic · Sep 2, 2020

Interesting article. I thought it made more sense for the coolant to flow through the head first and then the block as the head is the hottest part of the engine. Normally that is not the case. It flows through the block first and then the head. But apparently some engines are designed for reverse flow. Head first and then the block.

I also didn't realize that the thermostat on some engines opens up an internal coolant bypass when it's closed so the coolant can circulate. When the thermostat is fully open this bypass is fully closed and all the flow is directed through the radiator.

Coolant Flow—Normal and Reverse Flow

pmsmechanic · Sep 2, 2020

Egon said:
Misinformation?

View attachment 668402

Pretty standard configuration.

I'm guilty of it myself!

metalbender · Sep 2, 2020

Read the post about coolant flow. As far as I can remember the water pump draws from the bottom of the rad. That basic diagram looks like it's right out of my old text from 1967.

Tinhack · Sep 2, 2020

That "standard configuration" will work with or without a water pump and thermostat. As the coolant cools, it sinks to the bottom of the radiator and draws more hot coolant into the top. This cycle will continue on it's own as long as the engine is creating heat. There were no water pumps or thermostats on early cars. Look at the Ford Model N, R and S from 1906 to 1908 and the old Model T from 1909 until end of production in 1927. Higher horsepower and heat created the need for a water pump and thermostat.

GSVette · Sep 2, 2020

pmsmechanic said:
Interesting article. I thought it made more sense for the coolant to flow through the head first and then the block as the head is the hottest part of the engine. Normally that is not the case. It flows through the block first and then the head. But apparently some engines are designed for reverse flow. Head first and then the block.

I also didn't realize that the thermostat on some engines opens up an internal coolant bypass when it's closed so the coolant can circulate. When the thermostat is fully open this bypass is fully closed and all the flow is directed through the radiator.

Coolant Flow—Normal and Reverse Flow

Corvette LT-4 would be at least one of the reverse flow designs

rademamj1 · Sep 2, 2020

My understanding of cooling systems is also influenced by misinformation. Radiators are offered in a number of different configurations. These varying configurations are offered to influence; coolant movement and coolant plumbing methods. The most popular designs are down-flow and cross-flow. Each design carries its own advantage. Tractors use mainly the down flow radiators.

In the down flow radiator design the tanks are located at the top and bottom of the radiator core. The fluid enters through the top tank and moves downward through the heat transfer tubes with the help of gravity easing the work load of the water pump.

On the cross flow design used mainly by high performance and luxury vehicles, the tanks are located on the sides of the radiator's core, requiring the water pump to fully push the coolant across the core from right to left. Cross-flow systems are offered in a single pass, double pass orientation depending on performance and cooling needs. These cross flow orientations give the radiator the ability to cool the fluid multiple times, resulting in 12 to 20 degrees lower coolant temperature than a down flow radiator. Fluid movement within the cross flow radiator core is achieved only by the water pump. Since most overheating in tractors appears to be a limited issue, no tractor manufacturers have so far gone with a cross-flow design yet.