Temp gauge/water pump

[Daryl]

Was plowing the garden a couple of days ago and noticed the temp gauge had stopped working. Did a search here and found to ground the wire going to the sensor and watch the temp hand. Mine went to the red so I guess the gauge is all right, if I read the other forum correct. I don't know what to check now. It seems like I can hear a rattle in the water pump not bad and maybe I am imagining the noise. Could this be the cause? Is there a way to check the water pump? Could it be the thermostat? What should I check now?
This is on a TC30-- with 250 hours.

 

[jinman]

Daryl, there is a very good chance your problem is the thermostat. It could be staying open and keeping your engine so cool that the temperature gage does not work. It could also be the actual temperature probe, but not the wiring or the gage as you proved by the grounding test.

Several of us have had thermostats fail. There is a little bleed valve that gets stuck in the open thermostat (bad design problem). It holds the thermostat open and the engine never heats up.

You can measure the resistance of your temperature probe by removing it from the engine and placing its tip into hot water. You have to measure the resistance from the connection that goes to the gage to the outside threads surface while dipping the tip into hot water in a pan on the kitchen stove (or something similar if your wife revolts). The probe should read around 700 ohms at room temperature and drop to about 50 ohms at boiling temperature.

That's also how you check the thermostat. It should open in hot water and close when you remove it.

If you just want to see the resistance change on the probe, you can hold a match under the probe end for just a short time and watch the resistance drop, but you have to be careful and not overheat the probe.

 

[Daryl]

jinman
You are talking about the thermostat sensor? Sorry but not sure if you are talking about the temp gauge or thermostat.I took the panel off but getting to the gauge to remove it is going to be a pain. Hope I don't have to do that.

 

[Doc_Bob]

jinman
You are talking about the thermostat sensor? Sorry but not sure if you are talking about the temp gauge or thermostat.I took the panel off but getting to the gauge to remove it is going to be a pain. Hope I don't have to do that.

He is talking about placing the thermostat in hot water, bring it to a boil and see if it works.
Bob

 

[jinman]

jinman
You are talking about the thermostat sensor? Sorry but not sure if you are talking about the temp gauge or thermostat.I took the panel off but getting to the gauge to remove it is going to be a pain. Hope I don't have to do that.

Yes Daryl, I'm talking about the thermal sensor (temperature probe) that fits into the engine. That's what you disconnected the wire from to ground it, I think. It should have a spade type connection and be very near where the thermostat is on the tractor. It should be about as big around as a nickel and around 1-1/2" to 2" long when removed from the engine (about the size of a small spark plug). That temperature probe is what the 700 ohms cold and 50 ohms hot readings refer to.

I think your wiring and temperature gage on your instrument panel are just fine. If you grounded the wire and the gage went up to red, then I would concentrate on the probe or the thermostat.

DocBob is also right about checking the thermostat. If you take it out and can't see the "stuck pin" problem, then you can put it into boiling water and watch it work. That method works very well for testing thermostats.

BTW: You may need a new thermostat gasket when you remove it. If the gasket doesn't tear, you might get away without the gasket, but the safe method is to stop by your dealer ahead of time and have a spare thermostat gasket. The way I'd do it is to drain about a gallon of coolant (all drained is not necessary). Then remove the thermostat and check it. If you need a new one, you can go get the gasket and the new thermostat at the same time. If the problem is the "stuck pin" you can just cut the pin off and put the old thermostat back into your tractor. It will work fine without the pin.

 

[BobRip]

When you put your hand on the radiator hose is it hot (don't burn yourself). If it is only warm the most likely cause is the thermostat is stuck open. This is fairly common. When you pull the thermostat you can set that it is open. I would get a new one and replace the old one anyway if it has any age on it. You have to pull it to check it and you might as well put a new one in at that time. They do wear out.

 

[jinman]

Here is a picture of the problem many of us have had. The little stuck pin is highlighted in orange and you can see it is holding the thermostat open.

 

[Doc_Bob]

When you put your hand on the radiator hose is it hot (don't burn yourself). If it is only warm the most likely cause is the thermostat is stuck open.

Funny you should mention "touching" the tractor. As part of my preventive care on my TN, I routinely "touch" the machine when hot. I want to find out what is normal. How hot is the tranny, the radiator, turbocharger, hydraulic hoses, etc. I use common sense and never get burned, but maybe in the future, when I think something is "broken" I will have some idea of what is normal. Maybe I am just wasting time and risking a 3rd degree burn?
Bob

 

[Daryl]

I took the thermostat out today and the "ball" did have it locked open. I clipped it off ,put a new gasket on and refill with antifreeze. started it up and let it idol for maybe 30 min. The temp hand still only moved maybe an 1/8 in. Talked with the dealer and he said a new thermostat was $30. I hate to pay that for one if that is not the problem. It is in the mid 40's here so surely in 30 min it should be up to temp. Where should I go next. Does it sound like the sender now or still maybe bad thermostat. I took the rad cap off and could put my finger in after 30 min. It was warm but not hot.I could hold my finger in it.

 

[randy41]

it sounds like the thermostat if you can touch the coolant like that after running it for a while. i dont really know that you could do this but if you know what your thermostat is rated you might be able to find one at an auto parts store that fits and would be cheaper. you could take out the one you got and bring it with you...i think its rating is shown on it.
i live near you...what tractor store do you deal with?