190 degree thermostat in TO35

Back in July I had a problem with overheating and changed the thermostat and antifreeze. I tested the thermostat that was in the 35 and it was only opening about half way so I replaced it and the antifreeze. Temp gauge always showed 200 plus degrees while bush hogging and thought it was because it was pretty hot this summer. Well I blew the head gasket. I realized it when I changed the oil and antifreeze came out first. I sent it to the shop and while it was there I was cleaning out the garage and notice the old thermostat. gave it a good looking over and saw the it was stamped 88 degrees C.. which is equivalent to 190 degrees F . The one I replaced it with is the correct one 160 F. Could that be the reason for the blown head gasket due to the thermostat not opening fully.
Heres a little conversion formula: Celsius temp times 1.8 plus 32 = Fahrenheit temp

It should work fine with 190 thermostat, you have another issue.

did you check the radiator
many times they are plugged up in the center and coolant has to go around the sides, best way to check is with a digital temp gun so you can check the temp at all corners and center also do a flow test.

I would have the radiator checked out by a radiator shop before you put the motor back together.

do you have the fan shroud in place around the blade,
may need to buy a debris screen for the front of the radiator grill

might as well change the water pump while you are at it.

have heard of the water pump impeller coming loose from the shaft, so its just spinning, but not pumping water or the pump impeller fins eaten away and not pumping the proper amount of water.

the coolant system on these tractors is right on the edge, you must have all systems on go or they can over heat and you blow a heat gasket.

let us know what you find wrong,
((do you have a manual for the tractor to determine the correct temp thermostat))?
do not guess, be sure

I just run the radiator cap loose on my old tractor, the radiator shop man said to do this as these old radiators cannot take too much pressure, has worked well for years.

radiator hoses can get soft and collapse stopping the flow of coolant, install new ones and a new fan belt,
should be good to go,

The radiator is okay. After I installed new thermostat I had excellent flow. I do have all the manuals and it calls for a 160 degree thermostat. The shop changed the water pump also, he had said it was loose. New fan belt also and there is a fan shroud. I did have a problem with the temp gauge. Last time back in July before I sent it out I used the tractor and the temp gauge didn't respond at all. On a good note, at first I thought it might have been the liners and O rings that were bad due to all the antifreeze in the oil but luckily they are in good shape. They also sent the head out to machine shop to make sure it wasn't warped. One thing I did notice is that when I put in the new thermostat before I had the service done the temp never went to 200 degrees but at that point the damage was done. He's dropping it off this Tuesday so I'll see how it goes. I did remember you saying a while back about not totally tightening the radiator cap and took your advice.

I'm thinking the other issue Dave mentions is the water pump possibly not pushing enough in combination with the bad thermostat. Any way got a tune up, gouvener adjusted and had the ignition put back to factory speck. The previous owner by passed the safety switch and had a remote hand held starter on it which I hated. I'll let you guys know Tuesday how it is.

Running with a loose cap can be a double edge sword. The closer you get to 212 degrees the more you need the pressure to keep the water from boiling. The pressure increases the boiling point, however if your tractor never runs above 170-180 then you probably would never need the pressure. I recently replaced the radiator cap on my TO-20 because it was starting to boil over while working hard on 98 degree days. The cap that was on it had no spring or washer. It was just a cap that someone had put on there. I put a proper cap on it and the problem went away. The reason you might have gotten a 190 thermostat in your tractor is because that is the standard temp for a Chevy thermostat and the Z134 engine uses the same style thermostat. I would say somebody at some point just went to an auto parts store and just purchased one and put it in.

That was my opinion also, but heck of a cost for a wrong thermostat. I don't think the previous owner was not to interested in proper maintenance. A lot of things he did were just so the tractor ran. I'll know Tuesday if all is well.