Steve, you have a Caterpillar C-9 what is your engine serial number. Is the prefix start with
9DG, the engine serial number is ever so important to assist you with problem. Let’s first go
with prefix 9-DG . You indicated heating problem. Heating up running the flat roads or steep
long grades, are you losing coolant if so what are you adding, maybe this will get started with
taking a shot on guessing on serial number. Your engine has ( 2 ) temperature regulators
that will start to open at 191 Deg F and Full open at 208 Deg F. Next coolant loss looking at
Little rubber hose just under the radiator fill cap, than follow hose down to end of hose. What
you are looking for is the little wet on outside of hose about 1 to 2 inches, than tip hose so you
can see inside of hose ( is it dry and dusty inside or wet from coolant escaping) this is real
Important to determine your problem. This is a very common question I ask to determine
Stuck temperature regulator it faulty heat indicator bad connection or bad indicator. Last
question technical Cat information recommendations change out temperature regulators every
two years. Dave Atherton Retired Cat Mechanic