xps 8300 starts clicking after a couple of hrs

It is important to isolate where the sound is coming from.  If it is your drive clicking, it may die completely any time.  If it is a fan, it's not much to worry about, but something you would want to contact Support for eventually.  Make sure you have any important data/settings backed up, then I'd recommend running diagnostics on the drive (probably F12 when the system is powering up - or you might have a utility disk that came with the PC).  If it passes or you are pretty convinced it is the fan, open the case (with the PC off), and reseat the fan(s).

Thanks for the suggestion. I'll run the HDD diagnostics right away. I am pretty sure it is a fan but I'll try and rule out the HDD first.

If it is a fan how do I re-seat it? I have never heard of doing that before and have no idea how it is done.

Thanks for your advice.

Some fans connect directly to the board, others have cables.  The 8300 has cables for the fan.  Reseat the cable connector for the fan on the board.  Remove the fan to make sure nothing got lodged in the fan itself. support.dell.com/.../fan.htm

The diagnostics show the HDD to be perfectly fine. I was able to remove the board fan and dust it off. But the CPU fan was too tight for my tools. I was going to start stripping the heads if I tried any more force. This was just for the screws connecting the fan to the heat sink. I didn't want to remove the entire heat sink assembly as I don't have any thermal grease and have never had to do that before. So I simply dusted it off in situ.

I did find a loose connector clamp that I was able to reseat.

But it appears that none of these helped. I can hear the light click occurring again. When I look at the spinning CPU fan it appears to me that the center of the fan is not spinning exactly centered. I wonder if the spinning pin is slightly off?

Sometimes there is a sticker on the fan that can have a sort of "spiraling" effect, making it look like it wobbles when it spins.  I would call Dell support on Monday for further instruction and possible fan replacement.  If you could isolate exactly where the sound is coming from, it would really smooth the way for when you talk to them about it.  You wouldn't want to run without a fan for an extended amount of time, but several minutes will not damage anything.  You might disconnect a fan, rotating through all of them that you can disconnect, to see if you can isolate which is making the sound.  If you can call Dell and say such-and-such fan is making a sound, and that you already reseated and cleaned it out, their next step should be simple and quick ... replace the fan.

I think it must be the hardrive. When either fan is unplugged the vibration sound still occurs. I cannot think of anything else it could be - the two fans and the HDD are the only moving parts (when the optical drive is not in use).

Guess I'll have to call in. What a pain - I am rarely at home when their hours are open.

Is is more of a clicking noise or more of a vibration?  Vibration could be anything within the frame (probably connected to the drive cage).  If it is more vibration than clicking, try touching various parts of the chassis to see if you can absorb some of the vibration.

Phone is one option, but they also have chat (although not sure if their hours are any different), and email support.

support.dell.com/.../contact_technical_support

I would describe it more as a vibration.

I spent a few minutes (close to an hour) on the phone with a Dell tech tonight. He walked me through re-seating both fans and re-seating the cables for the HDD and optical drive.

However, after a couple of hrs the vibration noise is back.

Dell Support is going to call me tomorrow night to follow up but maybe if it is simply vibration there is nothing they can do about it? That would be so sad because I was so enjoying a silent computer for a change. My last computer the fan sounded like a plane in comparison. This Dell XPS 8300 has been so silent up until now. Would be disappointing to lose that.

The clicking sound is called 'the sound of death'.So your hard drive is dying.You had better backup all your data in case it die and you lose all data.