I have a 93 Toyota pickup. a few days ago the temperature gauge quit working. I now, have it overheating and shutting down. Could it be the thermostat stuck open/closed? or sending unit? or....PLEASE help. I am female but not totally mechanically illiterate. I have done a lot of maintenance on my vehicle, and usually can handle the issues but my time is limited to work on it right now and i need help. Thanks a bunch in advance. oh, and there is plenty of coolant in the radiator. and everything else was going good until a few days after the gauge stopped.
It is possible the thermostat is stuck closed.
You can test the gage by taking the wire off the temperature sensor and grounding it, the gage will move from cold to hot when grounded. If this happens change the temperature gage sensor. If the gage doesn't move then it may be the gage or related wiring causing the problem. The wire should be a single yellow and green wire on the sender.
If you take the radiator cap off and insert a thermometer into the neck of the radiator (one that can read about 260 degrees and can get wet). A cooking thermometer for oven meat can be used if you can't find the proper one. You can monitor the temperature of the coolant. The temperature should rise quickly when the thermostat opens.
If the engine is clearly ready to overheat and the gage is just warm then I recommend you look into the thermostat being stuck closed.
If the clutch on the fan fails it can give you a overheating condition when driving around town or in traffic.
With the radiator cap off always stay clear of the opening of the radiator when running the engine to avoid any coolant that may shoot out if the system is malfunctioning.
Try these few suggestions and let me know how you make out.