Yes, low coolant will cause it to overheat without the AC; that is not the only reason that will cause overheating however.
Any coolant leak can cause an overheat.Any coolant leak can cause an overheat.
Air flow. Check the electric fan, check the coolant, and might be time to replace the rad. Does it overheat at idle, and/or on the hi-way?
YesYes
A leaking heater core will cause the engine to overheat because the coolant is leaking out.
We are afraid to use the unit 24 hours because it might cause to overheat .What is really the cause of overheating?
It willl overheat when it gets low on coolant.
it is possible for heat from combustion to cause an engine to overheat quickly depending on where the gasket is blown, but i would look for a lack of coolant circulation first. if your coolant is not getting out of the motor and into the radiator it will overheat very quickly.
Yes, if it is not holding pressure or is allowing a coolant leak.
It can prevent coolant flow, which can cause a catastrophic overheat.
a leak
If coolant is up to proper level and cooling fans are working - should not overheat
If by water you mean engine coolant, yes. Loss of coolant, antifreeze, is a major cause of overheating.