How on earth do I access this thermostat??? (TYM 550)

[WranglerX]

True, the temperature sensor or gauge could be the problem, though the uneven heating in the radiator makes me question that possibility. Where's the best place to measure the temp and what should it be?

Old fashioned thermometer in top radiator tank...

Dale

 

[slimcity9]

I would try good radiator flush and new pressure cap before I brrow down layer by layer to get to thermostat...
...
Dale

Thanks for the suggestion. This is something relatively simple to try and if the thermostat is stuck it could even free it.

 

[slimcity9]

Old fashioned thermometer in top radiator tank...

Dale

What will results mean at this location? If the thermostat is stuck closed then the top of radiator is still getting a hard-to-predict amount of heat via convection. I was figuring a reading should be via IR right at the thermostat cover, which also seems to have the tractor's sensor. What are normal operating temps (180 F?) and what is the usual red-zone temp?

 

[Semper Paratus]

Similar problem a few years ago on my 89 Chevy 1500. Kept running hotter and hotter, at least by the gauge. No bubbling or gurgling when I shut down. I put a new thermostat in it did a coolant service. Old stuff looked like new. Borrowed a laser pyrometer (Snapon) from my mechanic friend let it heat up. Shot the thermo housing 190. Redlined on the gauge. Sender unit was bad. Replaced with a capillary tube temp gauge. All good.

 

[radios1]

Any idea if/how that pipe detaches? It's the rigid metal tube below the lower arrow in the picture. Even if it has a fitting that unscrews from the thermostat cover the bend in it will prevent any rotation until the cover is freed anyway.

it should have an un-boltable connection at the top most end of it. also, you could check for proper flow by leaving the radiator cap off, starting the engine, and look for flow in the radiator when it gets hot. an open thermostat with a good water pump will make a very noticeable flow looking into the radiator!..

 

[slimcity9]

... Borrowed a laser pyrometer (Snapon) from my mechanic friend let it heat up. Shot the thermo housing 190. Redlined on the gauge. Sender unit was bad. Replaced with a capillary tube temp gauge. All good.

Hopefully my cheap IR thermometer will do. Thanks...

it should have an un-boltable connection at the top most end of it. also, you could check for proper flow by leaving the radiator cap off, starting the engine, and look for flow in the radiator when it gets hot. an open thermostat with a good water pump will make a very noticeable flow looking into the radiator!..

I'm not sure what you mean by the "top most end" of the heating tube. One end enters the thermostat cover as shown in the picture, the other end goes around the corner where there's a transition to a rubber hose that I assume eventually enters the cabin.

Thanks for the tip about looking for flow during warmup. I will put things back together and try that along with measuring the temperature.

 

[slimcity9]

Similar problem a few years ago on my 89 Chevy 1500. Kept running hotter and hotter, at least by the gauge. No bubbling or gurgling when I shut down. I put a new thermostat in it did a coolant service. Old stuff looked like new. Borrowed a laser pyrometer (Snapon) from my mechanic friend let it heat up. Shot the thermo housing 190. Redlined on the gauge. Sender unit was bad. Replaced with a capillary tube temp gauge. All good.

Well it's looking as though it's the same problem you had. The temperature at the thermostat housing was 190 degrees after a full warmup and some mowing in the sun. The temperature gauge wasn't going as high this time, but still was 70-75% of full scale, higher than it should be for a normal operating temperature.

I had a little too much coolant in the radiator to keep the cap on long enough to see any flow. But the temperature measurements seem to say everything's ok.

Now I have to find a new sensor or retrofit a new measuring system. Thanks all for the helpful suggestions.