Does the car have a control valve or does it adjust the heat by closing off the outside air? The valve if it has one would probably be under the hood in one of the heater hoses. If no valve, is the outside door closing? Control cable may be broken or have come loose on either end. I'm assuming the car does not overheat and the water is circulating. Get it warm and feel each hose where they connect to the heater core. If both equal, there has to be a door not closing somewhere. Too much outside air for it to heat up. Sometimes the simplest things are the hardest to find or see.
You need to check coolant temperature sensor and the water pump.
When the thermostat and radiator were replaced, coolant could have dripped into an electrical connector or a sensor could be disconnected or damaged. Check the temperature sensor and crankshaft sensors first.
Be careful there is a temperature coolant switch mounted next to the thermostat housing. I thought this was the sensor and replaced it by mistake. There is another sensor.
The temperature of the coolant entering the heater core is controlled by the engine thermostat. The engine coolant thermostat is generally located at the engine end of the upper radiator hose.
the hoses leading to and from your radiator might be clogged. If you had a rusty radiator, the rust may have clogged the hoses that carry the coolant. you should check all your hoses and even flush them out.
your thermostat is closed. needs to be replaced. inexpensive part but can save your engine from overheating.
The defrost is cooing your coolant by circulating the fluids through the heater core. Check the water pump to insure that its pumping and check the radiator for blockages in the fins. Also check for an air bubble that can happen when a thermostat is replaced.
likely possibilities are the following. Low or bad coolant , water pump, thermostat needs changing, clogged radiator or lines, coolant temperature sensor or radiator fans not coming on, head gasket Also check the radiator caps on the hose and the overflow container. That was my problem. One or both may have to be replaced.
Run engine to normal operating temperature witout radiator cap Observe coolant circulation If coolant blows out of radiator - could be a stuck thermostat If no circulation could be a bad water pump
The thermostat in a car regulates the coolant temperature inside the engine. When the engine is cold, the thermostat is closed, allowing the heat from the combustion chamber to heat the fluid (coolant) in the coolant galleys in the engine block. Once the engine reaches an optimal temperature, the thermostat opens, allowing coolant to flow through the radiator. The thermostat then controls the flow of coolant to hold the engine at its optimum operating temperature, irrespective of engine load and operating condtions.
If your radiator isnt leaking and car is having a over heating problem and coolant spewing out. Chances are your thermostat needs replaced. possible the radiator needs to be flushed. But more likley its thermostat
The thermostat.