Loosening Bolts on 550 Coolant outlet

I am not much of a mechanic, but I like messing around with the tractor. I have a 550 that is not heating up to working range and my thought is that the thermostat is stuck open. I took everything off to allow me to reach the coolant outlet fixture where it attaches to the head with three bolts. They did not budge. I sprayed them with Kroil and am letting it set for a while before I try again. Any hints if this does not work? Thanks for your assistance.

Kevin R.

I got the bolts loose after 1 week of soaking with Kroil and keeping trying. I whacked them with the flat chisel. Now I am ready to put the beast back together. Thanks for your help.

Kevin

Kevin

Just check it out first. There should not be flow through the rad until up to temp. If you can see flow, or rad is warm soon after starting, that might confirm your guess. How hot is it getting? The guage may be incorrect. They are not precision instruments, even when new.
Does it heat up more quickly when the radiator air flow is blanked off?
Find out before you break anything.
May not even be a thermostat fitted!
Biggest mistake is to dive in and replace everything before diagnosing the actual fault and then finding the fault persists. That is how a lot of vehicle service centres work - they just guess and expect you to pay for their mistakes. It may even be the block filled with sediment and insulating the sender unit if it has the expansion type fitted to the back of the block.
Regards, RAB

Good comments and I appreciate them. The radiator does heat up soon after starting. I needed to replace the radiator hoses and wanted to wash and flush the radiator. This machine runs great and everything works, but it has not had much maintenance.

Kevin