Temperature sensor reading too high?

   / Temperature sensor reading too high? #1  
Oct 11, 2022
Bobcat Ct225 John Deere b early 1940s 1973 129 cub cadet
I figured I'd start a new thread since the head gasket and radiator have been addressed.

The gauge on the dash stays in between the two dots at idle, once I work the machine or even drive it, it rises up to just below the red. I took a caibrated IR temp gun and took measurements from all over the block, head, radiator and coolant neck. came back at 130-160 despite the gauge on the dash reading just under the red. I ordered a new sensor and will know once it comes in the mail, in the meantime, has anyone experienced this? Am I wrong to assume checking the temp as described is a good indication the engine is not actually over heating?
   / Temperature sensor reading too high? #2  
I would feel very safe with the readings you described.
   / Temperature sensor reading too high?
  • Thread Starter
An update:

The gauge is still indicating the machine is over heating. The new temperature sender was not the move I was hoping for.

I guess my next step is cleaning all the grounds. I am also curious if I can thread an aftermarket sender into the factory location and use my own gauge or maybe use the factory sender and hook an aftermarket gauge up to it. I could also just buy an inline temp sensor.....
   / Temperature sensor reading too high? #4  
I would say the gauge, not being highly precise, is the culprit. You could put a mechanical gauge as you were inquiring, in the current sensor location.
   / Temperature sensor reading too high?
  • Thread Starter
Reporting the results of my trouble shooting, I sure hope this benefits someone, some day.....

I left the tractor with a family member whom has been suing it for months. Every time the gauge creeped up to the "H" he would either shut it down or idle it till the temps lowered.

Step one was to make sure the gauge is indicating that the engine is over heating. I was able to replicate that, and as usual, I when I hit the rad, coolant neck, engine block and head, the temps were all under 160

Next I tried running it without the outside air filter. I was hoping that it was just that choked for air. No change without the filter

Next I added a mechanical gauge where the factory gauge goes. It never rose above 150. Being a little hesitant about the accuracy of the cheapest temperature gauge at Auto Zone, I hit the engine and rad with the IR temp gun and a thermal image camera. Same results, normal temperatures.

Gauge or wiring issue? I took the gauge cluster and gauge shroud off the tractor and traced all the grounds to make sure they were clean. Next I took a ohm meter and made sure there wasn't any resistance on any of the wires that are connected to the gauges. All the grounds were clean and I had good continuity on all the circuits that I checked. I was confidant that the wiring was working as it was designed.

After a few cold snacks, I started looking at the gauge. It was getting 12.6v from the fuse panel, and putting 10.3v out to the sensor. The schematic that Bobcat puts in the manual is okay at best, so I could not figure out if 10.3v is normal. I had another few gold snacks and decided to microwave a mug of water and dip the factory sensor into the hot water. The water cooled to about 150 by the time I remembered that the sensor housing needed grounded to send the signal and rig that up. At 150 ish the gauge was almost at the H. I didn't think to take some pictures till it cooled to 130ish, the gauge was still showing above normal operating temperature.

I tried taking the gauge apart to see if I could calibrate it, I could not. I decided to clean it up and put it back. Whilst cleaning the gauge I managed to break it.

Bobcat and Kioti will not sell me the temp gauge only. Both will sell me the entire gauge cluster. Kioti wants about $640 and Bobcat is asking $540. I am on the fence about buying the gauge cluster. I already have over $13,000 into this $10,000 tractor.... I think it's cursed and want to get rid of it, but in the same breath will not sell it knowing it needs any work, like happened to me.......

Sensor rig.jpg
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   / Temperature sensor reading too high?
  • Thread Starter
I ordered a new instrument cluster and cover from BestLine, with the $28 shipping fee, the total came to over $750. I asked why I would be charged shipping when ordering from the dealer when the bobcat website offers free shipping, the parts lady just said "thats what they charge us".

I work during the day and spend my evening with my two young boys, so by the time I get out to the garage, it's late. I have installed the cluster, but haven't had a chance to test it. I will report back when I get the time to let it run and get up to operating temperature.