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MacBook's fans are revving up in the heat

I

InfiniteLoopy

Cancelled
Original poster
Dec 14, 2010
366
5
It's summer and that means that my late-2008 MacBook has its fans revving.

I've been monitoring the different components and the platter hard drive is around 40C (100F), and the CPU around 70C (160F), which both seem to be within acceptable margins.

The MacBook (on an aluminium stand so it's properly ventilated) starts off with no audible fan noise and gradually ramps up until it's unbearable at nearly 6000rpm (this takes a few hours of use), at which point I put the MacBook to sleep, and the fans drop to being inaudible again. I then wake it up again, and the fans gradually ramp up again (over a shorter period of time), I put it to sleep, then wake, you get the picture.

So I downloaded a utility that allows the fans' settings to be changed based on the CPU temperature. I was amazed to see that the fans responded to on-screen operations. For example, they would be about 3500rpm, but if I clicked on a link (in Chrome), they would ramp up to 4500+ then drop down gradually by themselves once the page loaded. If I clicked on another link or loaded another page, they would ramp up again.

A few observations/questions:

- The fans seem worse when using a 27" ACD. Is this possible? Would lowering the resolution of the screen help solve the problem?
- Nothing is abusing the CPU in Activity Monitor.
- Is it normal that simply clicking on web links and loading pages has such an effect on the fans?
- Would an SSD solve this at all? I'm thinking that maybe the better read/write speeds may tax the CPU less?
- Is there any danger to the machine having software arbitrarily messing with the fans' speed?

Any advice would be appreciated.
Thanks
 
Tuning an external monitor drives the gpu harder hence the extra heat. You mention 70'c but is that load or idle?
 
I checked it when the Mac had been on for about 7-8 hours, with 3-4 self-updating Chrome windows open and apps like Messages and Mail open. So I'd say "usual load".
 
InfiniteLoopy said:
I checked it when the Mac had been on for about 7-8 hours, with 3-4 self-updating Chrome windows open and apps like Messages and Mail open. So I'd say "usual load".
Click to expand...
Ok firstly chrome is very resource heavy so it'll be adding load and heat.

When was the last time you opened your MacBook and cleaned it??
 
I thought that the Chrome issue was mostly solved now. Is that not the case?

It's been a while since I cleaned it but what makes me think it's not dust is that it takes a while to get into the revving fans state, which makes me think that blocked fans may not be the issue.
 
Cleaning won't hurt but you shouldn't sleep it to stop the fans that just saturates the device with the heat.
 
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2008 MacBook - it's probably a good time to redo the CPU heat sink compound. That can sometimes make a lot of difference in the heat produced by your system.
And, that would also get you to the parts that you need to check for lower airflow - the fan, the cooling vents on the back of the case, etc.

Also, expanding on what Gav2k posted - if you sleep your MacBook, it just shuts the fan off. That would be a worse affect than just letting the fan run for a while. You can also turn off the display, or temporarily unplug the ACD.
If you often use that external display, that's likely the biggest cause, too, and another reason to do whatever you can to control the temps, which would include replacing that old heat sink compound. :D
 
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Thanks for your replies.

I'm going to try using the screen less, and also not force it to sleep when the fans become unbearable.

Would reducing the screen's resolution be helpful?

Would an SSD?
 
InfiniteLoopy said:
Thanks for your replies.

I'm going to try using the screen less, and also not force it to sleep when the fans become unbearable.

Would reducing the screen's resolution be helpful?

Would an SSD?
Click to expand...
An ssd would be helpful in getting the info to the CPU quicker but your CPU would still heat up.

Lower res on the external would help a fair bit.
 
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I was using my 15 year old iBook G3 Clamshell yesterday. Just simple web browsing, and certainly no video clips. A little later I watched one of my favourite DVD's on the same Clamshell. The OAT was 33 deg C (91 deg F). The fan didn't come on once (there isn't one). ;)
I'm all for progress and also have a rMBP, but some of the older Apple technology is truly remarkable with individual components that one can change out if required.
 
Gav2k said:
An ssd would be helpful in getting the info to the CPU quicker but your CPU would still heat up.

Lower res on the external would help a fair bit.
Click to expand...

Thanks, so I gather that an SSD isn't really worth it then.

Regarding the screen, I'll try dropping it to 1080p resolution to see what that does.

What do you think about these fan rpm control utilities? Should I be using one?
 
When was the last time you opened your older Mac Book Pro and clear the years of dust out of it. Plus like others said if you plan to get it really consider an SSD upgrade.
 
satcomer said:
When was the last time you opened your older Mac Book Pro and clear the years of dust out of it. Plus like others said if you plan to get it really consider an SSD upgrade.
Click to expand...

It's been a while, years. But I'm not really comfortable opening it up beyond swapping the HDD.

But an SSD wouldn't solve my problem, would it?
 
Replacing your hard drive with an SSD won't hurt anything.
Your Mac will respond faster.
But, if you are looking at an SSD to help with your heat issues, that would be less likely to help much.

The best result with moving to an SSD, would be that you can take the time while inside to clean your cooling areas, making sure that the fan is clean.
Again, you should consider replacing the CPU heat sink compound. Absolutely worth doing on your 8-year-old MacBook, and may be the best effort that you can do to cool your MacBook effectively.
 
Thanks, I know an SSD would speed things up but I may see what I can do without getting one first.
I'm not going to dismantle anything as I'd be worried I'd break it.

What are your thoughts on utilities that change the fan speed?
 
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