Assuming it did not overheat before you replaced thermostat and water pump you may have installed the thermostat backwards. It is also possible the cooling system wasn't refilled properly and was air bound.
bad water pump or thermostat. check both.
because the water pump is not working properly....
If you are unsure if it is heating because of a water pump or a thermstat, you can find out by removing the thermostat. If it still heats without a thermostat, then you know it is the water pump. Without a thermostat, the water flow has nothing to cause it to heat unless the water pump fails to circulate the water. No circulation of the water would cause the over heating.
You need a new thermostat inside the electric hot water tank, as it is faulty. There is also a reset button on the thermostat that you could try. Does it heat up until the water boils?
Water pump not pumping or a pluged radiater
maybe low on fluid? or maybe bad thermostat? or maybe bad water pump?
Stuck thermostat, clogged radiator.
Not installed properly? operating water pump in reverse direction?
thermostat is more than likely stuck shut from the overheat. Have to be changed.
Bad thermostat, water pump not circulating, low coolant level, head gasket leak.
Try changing the themometer
A stuck or incorrectly installed thermostat.