Have 93 Dakota 3.9 that the engine will not warm up. Replaced thermostat, flushed cooling system. Putting cardboard in front of the radiator helped. Any suggestions for a more permanent fix?

 

A few question:
- What is the temperature outside where you live?
- How long do you usually drive your truck one way?
- Are you sure the engine is not getting warm, or is the temperature gauge (you mightnot have a temperature gauge)or sending unit (on the engine) just bad? Also, do you get heat out of the heaters?

Do the following:
With the engine cooled off, take the radiator cap off. Start the engine up, and go back out front. See if there is water running out from the top raditor line. Since the engine is cold, there should be no flow. If there is, the thermostat is bad. After a few minutes (I can't give an exact time, it can vary a lot) the engine will get warmed up. Than, you will start to see flow. When you start to see flow, go back in the truck and check the temperature gauge (if you have one) to see if its showing the engine is warmed up. If not, either the sending unit is bad, the wiring is bad, or the gauge is bad.
Also, after a couple minutes after the water starts to flow through the radiator, turn your heater on. If you don't get warm air, its probably because the heater core is plugged up (here is a how-to). Also, feel both line running to the heater core (located near the brake booster, two lines running through the firewall), both lines should be warm. Again, if one isn't warm, your heater core is probably plugged.

 

Once they are plugged they are a bear to get them to work right. It seriously sounds like your heater coil is the problem as mine did the same thing twice.

 

Is the motor actually not warming up or are you talking about the gauge not indicating same. The engine has to warm up when it runs, theres fire in them holes????????

 

You need to back flush the heater core. I installed two prestone flush tees inline with the core on the input and out side of the core.I clamp the hose on the radiator side of the tees and flush the core with fresh water every year. For some reason this design lets the gunk in the system settle at the heater core.