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My Yanmar Tractor Appears to Be Overheating – Now What?

The Yanmar tractor cooling system is excellent --- yet can still overheat.

Let us take a moment and discuss how to determine if your tractor is overheating and what you should do next.


First, you need to determine if it is overheating. For instance, if all your water is boiling out of the radiator --- it could just be a blown head gasket.

Check the water temperature with a thermometer or mechanical temp gauge. Be sure it is too hot. Many times, people mistake overheating with a blown head gasket.

Here is how to test it.

Cool your tractor completely. Fill your radiator with water. Start the engine with the radiator cap off. If you see consistent bubbles in the radiator when the tractor is running, then you likely have a blown head gasket.


The temperature light may be on. But that may not mean the engine is too hot. Occasionally temperature switches get weak. When this happens, the light comes on too soon.

Purchase a cheap thermometer. Place it into the water in the overflow bottle. This will tell you the temperature of the water and rule out electrical problems. The temperature light should come on around 220 degrees. If the thermometer is under that temperature you may need to replace your switch or may need to look for other possible causes.


Yes, it is normal. This does not necessarily mean that it is overheating. This happens when the water heats up and expands. It just needs somewhere to go. Once the tractor engine cools down, the water should be pulled back into the engine automatically. Now, if the water is boiling out of the overflow bottle, it is probably too hot, or you have other issues.


Be sure your radiator is clean on the outside.

If you have tiny pieces of grass and straw plugging up the fins, then the air cannot pull the heat out of the radiator and the engine will get hot. Even having a small percentage of the radiator blocked can cause problems. Use compressed air to blow out the fins. Never use a pressure washer on a radiator. Also be sure that the outside fins are all open (not bent in or crushed) and the holes between the fins are all open and clear.

Be sure that the radiator is clean on the inside (flushed out).

Keep in mind that just because you can put a hose in one end and the water shoots out the other does not mean that your radiator is working correctly. There are many tiny passages inside the radiator. The water may not be passing through enough passages to cool efficiently.


Make sure your belt is tight. The belt drives the fan and water pump. If the belt slips, your water pump, and fan won't spin fast enough.


Remove your hoses and be sure the inner linings are still intact.

An inner lining can separate, causing a bubble. This can block the water flow.


A dirty or clogged air filter will cause the tractor to heat up faster and work harder.

If all the above checkout, you may be working the tractor too hard. In the summer heat, the tractor may not be able to perform at 100% for extended lengths of time. This is especially true if you have an old radiator that may not be working at 100% efficiency. If you find that you are still having overheating issues, contact your dealer or local mechanic right away.

If you need any further help or have any questions about tractor engine issues, or anything else, please contact your dealer, local mechanic, or call us at 602-734-9944. Please ask about our current new and used tractor supply.

Team Tractor and Equipment - #1 Tractor Dealer in Arizona. We sell and service most major brands of tractors including Yanmar, Kubota, John Deere, TYM, Mahindra, Kioti, Case, New Holland, Massey Ferguson, Ford, Deutz, Case IH, Farmall, International Harvester, Branson Tractors, LS, Shibura, Claas Tractor, McCormick Tractors, Valtra, Solis, YTO, Montana, and Nortrac.

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