JD 5320: Any idea on the most likely cause?

ClemBert · Nov 30, 2012

While moving some large hay bales around today I noticed the temperature gauge was sitting in the red zone as high as it would go. I immediately stopped the engine to take a look under the hood. I noted that the radiator overflow reservoir was sitting below the "high level when hot" line. I opened it up and stuck my finger in the coolant. It felt like it was about 110-120 degrees. The fan belt is tight and operational. I did not attempt to open up the radiator fill cap as the gauge said the tractor was overheating. I did not note anything to indicate the engine was super hot based on observation and smell. The ambient air temperature today was around 75 degrees. Not a hot day at all and moving hay bales is light work at low RPM. I will have to wait for the tractor to cool off before I can flip the key to the run position to make sure it is sitting at "cold". I did however note that when the tractor was hot that turning the key to the off position the temperature gauge did fall back to the cold position but went back to the hot position when turning the key to the run position. Clearly, it is not stuck. The fuse associated with the instrument panel is good.

Just off the top of my head I would think that either the thermistor has gone bad or the tractor coolant really was hot and perhaps the thermostat has gone bad. Do any of you have experience with particular problem? If so, what should I look at and what is the process to eliminate potential problems one at a time to identify the problem?

Tx Jim · Nov 30, 2012

Possible faulty temp. sensor

greg_g · Dec 1, 2012

My 3720 overheated once. And I was a bit confused when I raised the cowl and saw plenty of coolant in the reservoir. I gave it an hour to cool down, then popped the radiator cap - and saw the fins. So for whatever reason, coolant was not being drawn from the reservoir to replace what was missing (for whatever reason) from the heat exchanger. I topped it up through the radiator opening, put the pressure cap back on. Never had a problem since.

//greg//

JD 4520 · Dec 1, 2012

Clean the outside of the radiator to make sure it doesn't have hay dusk and other debris the blocks air flow and once it cools down you can check the coolant.

Anytime that I have had an overheat problem on any vehicle - tractor included- I like to idle it at 1200 - 1500 RPMs to get the flow going and not just shut it down overheated. You can displace a lot of heat by doing this procedure first.

ClemBert · Dec 1, 2012

Yes, I forgot to mention that there wasn't anything blocking the radiator, grills or airflow.

ClemBert · Dec 2, 2012

I had a chance to diagnose the problem today with the tractor sitting cold. The problem is clearly the temperature sender (thermistor). The temperature sender on the Powertech 2.9L Diesel engine is located on the top-left-rear side of the engine block as show in this picture.

To test if the temperature gauge is bad you unplug the white wire from the temperature sender while the key is in the run position. If the temperature gauge shows "cold" (needle sitting to the far left on the stop) then this indicates the temperature gauge is working normally. Next, you short the white wire to ground. Again, with the key in the run position. The instrument gauge should show "hot" (needle sitting to the far right on the stop). This tells you the temperature gauge is working normally. By process of elimination the culprit is the temperature sender.

To verify that the temperature sender is, in fact, bad you remove the temperature sender then measure the resistance of the sender in different temperature water as shown in the chart below.

The part number for the temperature sender is RE51774. The cost is approximately $35.