Is my iMac getting too hot?

Yes it appears to be running pretty warm. I would recommend doing a SMC reset and also a PRAM rest, this may help. You may need to do each multiple times. You didn't say what you're doing with the computer to get it so warm but I'm guessing some serious music production or 3D Graphics. Fortunately the machine will shut down if it senses it's running too warm but I'd recommend trying to cut that off at the pass. Make sure it has adequate ventilation and it wouldn't hurt to have an external fan blow on the back however away from the exhaust vent. This will help dissipate some of the heat.

SMC RESET

• Shut down the computer.
• Unplug the computer's power cord and all peripherals.
• Press and hold the power button for 5 seconds.
• Release the power button.
• Attach the computers power cable.
• Press the power button to turn on the computer.

PRAM RESET

• Shut down the computer.
• Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
• Turn on the computer.
• Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
• Hold the keys down until the computer restarts and you hear the startup sound for the second time.
• Release the keys.

Believe it or not watching videos is taxing on a computer however I think it should run cooler than that. Also when you notice high temperature open Activity Monitor (Applications - Utilities - Activity Monitor) and look for any processes that are using a large %CPU (look in the columns) and if you see a process taking a large percentage that is probably the reason for the high temps. Also while you are in AM click the System Memory tab and see how much FREE RAM it has. Do this when the temps are high, as a general rule if a system has 500MB or less of RAM then it could benefit from a RAM upgrade.

excuse me for intruding in here but i have a similar problem with my imac (3.06 ghz intel core i3, 8 go 1333 mhz ddr3, macintosh hd) where did you get all those temperature readings? i cannot find this feature on my machine. thank you.

It's OK, but next time please create your own post. Download and install iStatPro, you can use Google to find it.

thank you sir!

RvdH wrote:

I know nothing about the inside of the iMac 27" (late 2009 model). Is it possible that while replacing the LCD panel the mechanic has misplaced a piece of plastic eg that now blockes the airflow? Or could it be that the panel is hotter than the original one?

Would it be a good idea to have the planel replaced by another one again?

Any other suggestions?

It's not likely any air flow was obstructed however it is possible that when the computer was put back together a temp sensor cable was not connected. If you noticed the problem immediately after the repair then you should have take it back immediately. I would recommend taking it back to the same AASP or Apple Store to have it looked at.

I doubt the LCD is causing the problem. However when you get the system back make sure you have it looked at before taking delivery to monitor the temps.

Wow glad that was it, first time I've seen that issue!

I agree with your observations. Changing the LCD does lower temperatures to normal.

My 21.5" iMac 2.5 GHz Intel Core i5 was experieincing high temperatures under 100% load on all cores. I used iStat Pro to increase fan speeds to 2200 RPM in order to lower secondary heatsink temperatures below 80C.

Last week, the iMac showed signs of LCD persistence as a smudgy dark vertical line under the Apple logo. It took almost 3 days before it cleared despite using every trick to reverse LCD persistence. In the meantime I request Premium Serivce and the LCD was replaced. Secondary heatsink and power supply temperatures are now 10C cooler and I no longer need to increase fan speeds. Maximum secondary heatsink temperature is 80C, primary heatsink 65C, power supply 70C, all CPUs below 60C. Fan speed is default 1200 RPM.

I cannot explain why this works. I did have the fans vacuumed while the LCD was removed but there was very little dust after 10 months. Dust does not seem to be a factor. I can only add that the solid desktop colours are now lighter than before even after lowering brightness to 50%.

Here's data from my 21.5" Imac after changing out the LCD. 4 cores running 84% doing a sustained photomerge. Fan speed 1200 RPM. Previously, I would need to use 2200 RPM to effect the same cooling and also use additional external cooling on the secondary heat sink.