I apologize for the long post in advance. The issue isn’t with my truck, it is with my commuter car. It’s a 2002 Taurus with the 3.0 DOHC (Duratec) V6 engine. Issues started last year when the water pump began leaking out of the weep hole. I replaced the water pump with a new unit, changed the hose assembly, thermostat, flush/back flushed the system, and replaced the coolant. I had some issues with getting an air bubble out of the system and the motor got hot a couple of times. During the process I lost the reservoir cap, and replaced it with one from the junkyard.

As soon as the repairs were completed and the air bubble was out, the motor starting getting very warm – not all the way to hot but about 3/4s of the way to H when idling after I got off the interstate. I could rev the engine to about 1800-2000 RPMs, and the needle on the temp gauge would drop to about half way with in ~15 secs. A buddy was headed to the junkyard, so I told him to grab a water pump off a junker just to experiment. The car ran fine with the junker water pump…except sometimes the low coolant light would come on, even though the coolant level was full.

Back in May I was out of town for the night, and my wife drove my car. To make a long story short, I came back to find the hose assembly had a pinhole in it; I replaced the assembly (~$125!) under the part’s warranty. At that time I noticed the car was getting hot again while idling, after it had been driven for a while. Again, if I revved up the motor, the temp would drop. I replaced the water pump (again) with a new unit. Same thing – it gets very warm, though not quite all the way to hot, and I can rev the engine and the temp will drop; however, the low coolant light no longer comes on. Also, both cooling fans are running.

So what do you think is the problem – an air bubble? Bad thermostat? External fins of the radiator clogged? Internal radiator issue? Something else I haven’t thought of?

Thanks in advance!

 

Air bubble is still in there somewhere.

 

I guess I should've also mentioned I've been parking on the side of hill where the reservoir is the highest point, to try to get the air bubble out (if present). The coolant level hasn't changed.

 

Park it with the reservoir at the high point, remove the cap, and let it idle for 20 minutes.

 

I thoroughly flushed the cooling system, paying extra special attention to flushing the radiator. The temp is behaving again; however, the "low coolant" light has a come on a couple of times, even though the coolant reservoir is filled to the appropriate level. The light has come on a few times after driving ~20 min, then it is off again after the car is started the next time.