Fan whirr, 75% idle and 5300rpm -- help!

Use iStat Pro or iStat Menus to see the CPU and HDD temperatures?

Have you tried an SMC reset?

Have you reset the SMC yet?

64°C shouldn't let the fans spin that high. Have you installed any fan control software?

radicaldog said:

Will try the reset tomorrow. Recommended fan control software?

Click to expand...

http://www.macupdate.com/info.php/id/23049/smcfancontrol
http://www.macupdate.com/info.php/id/23137/fan-control

You might have a faulty internal temperature sensor. If the Mac detects no reading from a sensor it can go into fail safe mode where it runs the fans at full speed.

Run Hardware Test (on the install DVD). That will show up any faulty sensors. Sensors are quite cheap to fix.

edit: I would not install fan control software yet. I think you may have some kind of problem. IMHO you should try and resolve the problem rather than just masking it with fan control software. Otherwise you might cook some internal component.

You might want to take a look at this thread - very similar symptoms
https://forums.macrumors.com/threads/954136/

What are your temps and fan speed at idle ie all programs closed, Activity Monitor showing <2% CPU?

If your fan always runs at 6200 rpm that's the symptom of a bad temperature sensor. But from your earlier post it seems to vary from 5300 up to 6200. Therefore I don't think it's the temp sensor (sorry, I should have read your post properly).

Could you post all your temperatures when the fan is at 6200 rpm? You can take a screenshot of iStat and post it here. (reason - it's possible that some other component is hot & the fan is working to cool that. Your HDD is warm but not amazingly so).

Blocked air path? When the fan is at 6200 rpm, you should feel a strong air flow out of the hinge.