VENT TO HEATER CORE IS NOT CLOSING................
The normal hot water heater temperature setting is typically around 120 degrees Fahrenheit.
This would indicate that the system is low on coolant when the gauge is hot. Not enough coolant to service the heater core.
Possibly a faulty coolant pump.
No. You may be leaking engine coolant from the heater core or leaking refrigerant oil from the AC evaporator.
Drain radiator RE-fill slowly to prevent and "air lock" Run vehicle to normal operating temperature with heater on Check coolant level
NO! 100-120F setting normal. 140F can cause accidental scalding.
If the coolant level is okay, I would suspect a restricted heater core. Try flushing the heater core.
Low coolant? Thermostat not closing allowing engine temperature to get to normal operating range? System air bound? Heater core plugged or restricted? Water pump not circulating coolant?
Open drain plug at lower end of radiator Run engine to Normal operating temperature with heater on -no higher When draining stops -- close drain plug Refill radiator slowly to prevent system from becoming "airbound" Start vehicle - bring up to normal operating temperature with heater and re-check coolant level
It is possible a little low on coolant and has an air bubble in the heater core.
No, I would suspect a stuck open thermostat, a failing (worn) water pump or clogged heater core. Also chedk for a sticking heater control valve in the coolant circuit if fitted. It could also be a internally swelled heater hose from the block to the heater core blocking proper coolant flow..
With engine coldDrain coolant from radiatorRemove hose clamps on defective hoseRemove defective hose and replaceRe-fill coolant slowly to prevent an air lockStart engine and look for leaksRun engine to normal operating temperature with heater onRe-check coolant level