So, since I am going to go through the normal litany of possible causes, I thought it might be fun for members to throw out their best guesses as to the problem and see how well we do. My radiator froze and cracked when we had unusually cold weather and I had no anti-freeze(my bad). So it had been leaking 1 quart a day driving in and out of town-20 miles. It never over-heated, ever. So I replaced the radiator yesterday and topped it off and power-burped it. I used a flusher to force fluid through the system to get all air out of the system. Now when I run the car it overheats and starts spewing coolant out the overflow reservoir as soon as it reaches running temp. The biggest clue is the fan is no longer running-it ran yesterday before the radiator change and even when the car is boiling the coolant out, the needle never raises above the middle of the gauge. I have checked all connections and have verified the fan is still operational, connecting it directly to the battery. My guess is the CTS has gone wiggy, but I find it hard to believe the CTS would just crap out at the exact same time the radiator is replaced. Anyone care to take a guess? 94 Plymouth Acclaim 3.0L 200k miles-all original. I have bought a new thermostat and CTS to start the project.

 

My car was doing this when I had an air pocket in the system, they're a pain to get bled completely.

 

You know, before I put the new parts on, I think I'll drive up on ramps to get the radiator to the highest point see if that will do it.

 

I actually also had a bad radiator cap and my system couldn't build proper pressure. Wasn't overheating though.

 

So I replaced the radiator, coolant temp sensor and thermostat. When I ran the car, I heard the fan relay "click" when it got up to temperature but the fan never came on. So the problem is in the wires to the fan or the fan itself. Any ideas on what I can directly wire the fan to that only has power when the ignition is on? I was thinking the line to the coil pack(yes it has a coil pack and not a coil-it's a Mitsujunki engine).

 

The reason for the over-heating is simple: the connector for the radiator fan can snap together even if it is slightly cocked to the side. The 2 prongs were not sliding into the female side. After ensuring the proper connection, everything works as it should and no overheating. But I still believe the CTS was bad because the gauge never showed hot even when the coolant was gushing out the radiator and reservoir. But altogether, it was $73 incl tax to replace the radiator, tstat and CTS. And it wasn't even the Mighty K's fault. I only had water in the system during winter. Thank God it didn't damage the engine, just a cracked radiator.

 

Long live the Mighty K!

 

Good to hear all's well. Gotta love the K's