Increased RPM on 2002 Ford Explorer XLS

[jdp12678]

I have a 2002 Explorer XLS that has approx 125,000 miles. Recently the RPM's at Idle are running around 1,200 - 1,500 during the hot part of the day, I am not sure but I believe that normal RPM at idle would be 700 - 800. This is causing some worry as I do not want the vehicle to overheat, the increase in RPM has resulted in rising temp but not redline. I replaced the radiator about 1 1/2 years ago. I know the pump is working properly b/c I can see the coolant cycling in the fill tank. Any thoughts on why the RPM are running high would be greatly appreciated.

 

[E.B. Cornburner]

You most likely have a vacuum leak somewhere. Listen carefully under the hood while it's idling, and you might be able to pinpoint it. If not, have a helper shut the engine down while you listen under the hood. Might have to start and stop it a few times to find it, but it'll hiss for a second or two as the engine shuts down, and it's sometimes easier to hear with less other noises intruding.