Radiator fan loud

[rock9021]

I'm currently driving a 2007 Grand Marquis LS. I've noticed after driving for about 20 minutes the radiator fan kicks on high speed and it will not turn off until I shut the car off and let it cool. The car temp gauge sits consistently at half way point before fan kicks in. The main issue is the noise of the fan, it sounds like a jet plane or a loud vacuum. The noise is constant and doesn't change. Ive taken the vehicle to a Ford dealer with no success in pin pointing the cause. I was told the fan is just loud but its working fine. I acquired the vehicle about 6 month's ago and ive never heard a cooling fan stay on constantly. I was thinking about replacing the fan or possibly the water pump. I'm not sure if the car is suppose to run this hot. Any suggestions?

[sly]

what area do you live in? Here in Texas, that's normal in the summer.

[rock9021]

I'm in MD but even when it was cool outside I had the same issue.

[sly]

in that case... the temp sensor may be bad. It should be on the coolant crossover to the left of the alternator (looking at the engine from the front of the car) with 2 wires going to it. Test the resistance cold and at operating temperature (thermostat open) and see if it matches up to the chart here: http://oldfuelinjection.com/index.php?p=28

You can also backprobe the SIG RTN wire without removing the plug if you have those pointed probes, just slide it in next to the wire. If both wires read zero, you're either not making contact, or the sensor is shorted.

[rock9021]

I'll look into it, somebody suggested relay switch.

[sly]

the PCM controls the fans... so check the relays in the under-hood power box as well. I don't know how many it has as I have never dealt with the newer models. The switch for the system is programming in the PCM but it reads temps from that temp sensor.