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Farm Machinery Digest: Testing your diagnostic skills: Engine thermostats and BSFC

Ray Bohacz for Progressive Dairy Published on 08 November 2021

Situation No. 1

The weather is getting cold tonight, and you are glad the heater in the combine works well. You have about another 20 acres of corn to go, and harvest is complete. You can almost feel that warm bed and soft pillow now.

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Suddenly, the warning chime goes on, and you look at the engine temperature gauge. It is climbing with authority toward the red danger section of the gauge.

You kick the header off and throttle down the engine. The temperature is still going up, and the heater discharge is getting extremely hot. You shut the engine down, thinking you blew a hose, but you do not smell any coolant. You go and look, and everything is there. The belts and hoses look fine. Since it is not too late, you call four friends, and this is their advice.

A: Farmer A says the thermostat must have failed, so the temperature rose so quickly.

B: Farmer B says Farmer A is wrong; once the thermostat is open, it cannot close until the engine cools off, and then it could fail.

C: Farmer C is sure the water pump went, and the coolant is not being circulated.

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D: Farmer D says you ran the engine too long and hard, and it just needs to cool down.

Situation No. 2

Since you farm way into the Nebraska Panhandle and your ground is far off the two-lane road, there is no electric power, but you want to put in a center pivot to water some hay ground.

You need to buy an irrigation pump with a diesel engine and look at a few different brands. A potential brand lists one of the engine specifications as BSFC. You ask the salesman what that is, and he gives you some double talk and then admits he does not know.

The next week, you are at your niece’s wedding and, at the reception, you bring up the topic. This is what you are told.

A: Farmer A says it means brake-specific fuel consumption.

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B: Farmer B believes the term stands for bypass standard fuel control.

C: Farmer C says it has something to do with an emission control if the engine is polluting too much, but he cannot remember what the letters stand for.

D: Farmer D states it represents a bio-fuel diesel engine and can run on LP or diesel.

Situation No. 3

You are driving home from a growers’ meeting, and you get a flat tire. Your car only has a temporary spare. You put it on and drive to the next town to get the flat fixed with an inside patch. The repair shops state that their wheel balance machine is broken. So they will mark the tire where the weights and valve stem are and put it back in the same spot so it does not need to be rebalanced.

You are leery of this, but there is no vibration on the rest of the drive back to the farm. When you get home, you ask your friends if they ever heard of this.

A: Farmer A says that is nonsense – you must rebalance the tire.

B: Farmer B believes if you put the tire back on the rim in the same spot, it will remain balanced.

C: Farmer C states that the balance is really for the rim, making no difference in how the tire is put on.

D: Farmer D is honest and says he has no idea.

Answers

Situation No. 1: Farmer A is correct. Either the spring jammed in the thermostat or, more commonly, the seal for the wax pellet motor that opens the thermostat failed and the wax escaped. The molten wax works against the spring and forces the thermostat open. As the coolant warms, the wax melts, and as it cools, it solidifies.

Situation No. 2: Farmer A is correct. BSFC or brake-specific fuel consumption measures the fuel (usually in pounds) that it takes to make one horsepower for one hour. If the BSFC is 0.5 pound and the engine is developing 100 horsepower at that load, it would take the equivalent of 50 pounds of fuel for it to produce that power level for one hour, approximately 6 gallons.

BSFC changes with engine load and rpm.

Situation No. 3: Farmer B is correct. If you accurately mark the tire’s position on the rim and reinstall it in that orientation, the balance would be just as it was before the tire was removed. It would be in an acceptable range of tolerance. end mark

Email “The Hotrod Farmer” Ray Bohacz with your machinery-related questions. Visit his site – Farm Machinery Digest – for technical articles and to listen to his Idle Chatter podcast, which has listeners in 67 countries. Also tune into Farm Machinery Digest Radio on Sirius/XM Channel 147.

Ray Bohacz
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