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

[slimcity9]

My TYM 550 started overheating, so I'd like to pull the thermostat. But I cannot see how to get both bolts out of the cover, picture below. The arrows are where the bolts are. The upper right bolt has maybe just enough clearance from the exhaust connection for me to get a socket in there. But the lower left bolt appears hopeless, as it is directly behind the metal heater pipe. There must be some trick to it. Anybody?

 

[Alan W.]

Are you sure its the thermostat. I cant remember the last thermostat I had to change in any of my tractors or vehicles. Does it get hot from the start or does it rise while your using it. Have you checked to see that the radiator fins aren’t plugged with debris.

 

[slimcity9]

Are you sure its the thermostat. I cant remember the last thermostat I had to change in any of my tractors or vehicles. Does it get hot from the start or does it rise while your using it. Have you checked to see that the radiator fins aren稚 plugged with debris.

It's been gradually running warmer over the last couple years, in spite of regular cleaning of the radiator with compressed air. In earlier years the temperature gauge would always be around 50%, even during use. But 60-70% has become more common, and this last time I had just cleaned the radiator, gone out and started mowing when it kept on rising to 80+% or so. I think this tractor has its red band at about 90%. So I parked it and felt around. The top of the radiator was hot, but the rest of it was downright cool. The coolant looks to be in good shape: proper level and clear.

This model has AC, so the AC radiator catches the brunt of the crap that gets sucked in, mostly grass seed.

Because the exterior of the radiator looks ok, I figure the problem is down to interior plugging, a bad thermostat, or the pump. In many vehicles pulling out the thermostat for a quick test would be straightforward, but that doesn't seem to be the case here.

 

[RustyA]

Use an infrared thermometer to measure different spots on the radiator, guessing bottom of radiator internally gunked up making it harder to shed the heat. Thermostat usually works or it doesn't. I'm guessing if you open drain cock at bottom of radiator very little fluid flow due to gunk.

 

[radios1]

maybe the heater pipe has to be removed first, this reminds me of mercedes benz cars, where everything is close quarters, and you had to do a lot of disassembly just to do minor things!..

 

[Roadworthy]

I'd start with the infrared thermometer or some other cross check on your gauge reading. The gauge may be accurate but it would be good to confirm you HAVE a problem before seeking a fix.

 

[slimcity9]

Use an infrared thermometer to measure different spots on the radiator, guessing bottom of radiator internally gunked up making it harder to shed the heat. Thermostat usually works or it doesn't. I'm guessing if you open drain cock at bottom of radiator very little fluid flow due to gunk.

I had partly drained the radiator to remove the upper hose. Good flow and no gunk. After the overheating the top of the radiator felt to be around 150-170+ degrees F, while the middle and bottom were more like room temperature, 80-90 degrees or so.

 

[slimcity9]

maybe the heater pipe has to be removed first, this reminds me of mercedes benz cars, where everything is close quarters, and you had to do a lot of disassembly just to do minor things!..

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.

 

[slimcity9]

I'd start with the infrared thermometer or some other cross check on your gauge reading. The gauge may be accurate but it would be good to confirm you HAVE a problem before seeking a fix.

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?

 

[WranglerX]

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

Dale