The engine seems to be running too cold?

Based on the information you've provided, it appears that your 1996 Ford Ranger is running at a lower temperature than normal. There are a few potential causes for this issue:

Thermostat: The thermostat plays a crucial role in regulating the engine temperature. If it is stuck open or opening too soon, it can cause the engine to run cooler than normal. Consider replacing the thermostat to ensure it is functioning properly.

Cooling system blockage: Even though you have blocked off the radiator, it's possible that there may be a partial blockage elsewhere in the cooling system, such as in the heater core or coolant passages. This can restrict the flow of coolant, resulting in lower temperatures. Flushing the cooling system or having it professionally inspected may be necessary.

Coolant temperature sensor: The coolant temperature sensor provides information to the temperature gauge on the dashboard. If it is faulty or reading incorrectly, it can cause the gauge to display inaccurate readings. Consider having the coolant temperature sensor tested or replaced.

Heater control valve: The heater control valve regulates the flow of coolant to the heater core. If it is not functioning correctly, it can impact the performance of the heater and engine temperature. Inspect the heater control valve and ensure it is operating properly.

Engine management system: It's also worth considering the possibility of an issue with the engine management system. A malfunctioning sensor or incorrect calibration can affect the engine's temperature regulation. Having the engine management system scanned for any error codes and performing a diagnostic check can help identify any underlying issues.

Considering the range of potential causes, it may be best to consult a professional mechanic or Ford dealership. They can conduct a thorough inspection of the cooling system, perform diagnostic tests, and provide a more accurate diagnosis and solution for your specific vehicle.

Pat: Thank you for the suggestion. I did replace the thermostat... the old one was in pieces when I took it out. Installed the hottest one I could get (192 deg F). This didn't fix the problem. The problem is not one of heat in the passenger compartment but rather one of the engine not heating up. When it did on an earlier occasion heat up I had lots of heat in the cab. After replacing the thermostat: The engine temperature now rises at an even slower rate than before. It also does not get any hotter than before. When I touch any of the hoses under the hood they are barely warm. When the engine is at its hottest I removed the radiator cap and the coolant was just warm. I once again blocked the radiator off, turned off the interior heat, and drove the truck around the city for 30 minutes. The engine temperature went up some. The included drawing shows the maximum that the temp gauge roses to when the engine was at its warmest. Any suggestions will appreciated. Thank you. ~ Ray