A "bad" thermostat is probably one that is sticking. If it sticks open, the engine coolant will circulate through the radiator at all tiimes, making the car hard to warm up in the winter, and slightly less efficient according to the laws of heat engines. If the thermostat is stuck closed, the coolant will never circulate through the radiator, which could cause the engine to be damaged by overheating.
If your vehicle is running too cool, you have a bad thermostat. You need to replace it.
Vehicle will run without a thermostat - however will not run as efficiently and will have not heat
Yes
the temp gauge will run ot then cool that is when the thermostat is opening again
Yes It Can.
A Thermostat enables the engine coolant to heat up quicker. One of the advantages is that the vehicle heater will get hotter faster. When the temprature of the engine reaches about 92 degrees f the thermostat opens to allow the engine coolant to circulate to the radiator which maintains a safe temprature for the engine to run at. A vehicle will run without a thermostat fitted. But it is not recommended on some engines as it may cause a hot spot which could cause the head gasket to blow. A typical example being the Leyland O series engines from the 1970s
Could be a bad thermostat.
Plugged radiator Water pump Bad thermostat
If stuck open the car will run cold. If stuck closed the car will run hot.
It could be you have a stuck fan relay, a contactor that is sticking, or your thermostat is bad.
A bad thermostat or a bad clucth on the fan. Could be timing but not likely.
bad thermostat or water pump