Thermostat

[Bud Kaiser]

I have had trouble with my thermostat on my 450. First one stuck closed and blew my headgasket.I replaced the thermostat with a IH (high dollar) one this time along with headgasket.It was fine for a year now it is stuck open. I can tell it has circulation when cold and never warms up above 120 degrees. Have yall had similar problems. Which thermostat works the best for yall. I have never had any problems with my other(6) tractors in the last 20 years?

 

[David G]

I would expect you have a coolant quality issue.

 

[Bud Kaiser]

Nope fresh overhaul, block and radiator was cleaned 2 years ago I use a 50/50 mixture antifreeze and distilled water.

 

[old]

New stuff today is not made near as good as it once was so you may have just gotten a couple new junk parts

 

[CNKS]

If you mean in the winter those tractors will not get anywhere near running temperature without a load. As far as temperature, the clean block and radiator didn't help any, but is much better than running an old engine hot. I wouldn't worry about it.

 

[Janicholson]

Thee explanation is that the tractor was made when energy efficiency was pretty irrelevant. The thermostat housing is designed with a huge bypass port next to the thermostat connecting the engine to the top radiator hose. The flow rate of this bypass "bypasses" so much coolant that in cool weather, or winter, The thermostat never even thinks of opening. The simple solution is to restrict the passage with a thin stainless steel plate made in the shape of a standard gasket, except having only a 1/4" hole where the bypass is located. (This was dreamed up by another YTer this fall) in a discussion with me and the original poster (search if you wish to).
In all my experience with letter and up to 450 number series, they only work in the run range when pulling 50% power for more than an hour in 70 degree weather. Ignore it, or add the restrictor plate when doing work on it next.
It would sure make it easier to heat a heathouser, or keep the efficiency up a little if done. Jim

 

[Bob M]

Jim N hits it right on the head, both the problem and a good solution.

For a quick, low-cost alternative, use a winterfront over the grille to block most of the airflow through the radiator. It doesn't need to be fancy - a old poly feed bag with a couple bungees to hold it in place works fine.

 

[jdleach]

In addition to the above suggestions, go ahead and test the thermostat to see if it is indeed open. Take out the thermostat and check the valve. If it is closed, heat a pan of water and throw the thermostat in while the water is still cool. Using a simple kitchen thermometer, watch the thermostat operation as the water heats up. It should begin to open at around 160 degrees, and be fully opened at approximately 190 (these temperatures may vary dependent on the rating of the thermostat, but not by much). Of course, if the valve is visibly open when you remove the thermostat from the tractor, then it has issues and you will need another one.

If the thermostat operates as described, there is nothing wrong with it functionally. At that point, you can proceed to apply the fixes noted by the other posters.