System overload caused by erratic fan behaviour

I'm running Logic Pro X and processing audio with a combination of Logic Pro effects and a modest selection of third party plugins. A few days ago I started getting system overload messages on sessions that have previously been running without issue. CPU/HD both maxing out and refusing to play even 1 second of audio. I noticed my Macbook Pro (Early 2011) was getting extremely hot, but I wasn't hearing the fan. I checked the fan speed and sure enough, it showed 0RPM. So I shutdown, took off the back plate, removed the fan and gave everything a general clean (it was actually pretty dust and fluff free). There was nothing noticeably wrong with the fan so I put it back in, screwed the back plate on and fired up a moderate Logic session. Now the RPM showed readings between 2000-3000RPM on playback. So I commenced mixing... all was fine until about 6-7 minutes later when it started getting super hot again. I checked the fan and once again it showed 0 RPM. So I repeated the process - this time with a smaller session (only a few plugs engaged). But same thing happened; about 10 minutes of normal operation then heat and system overload. Something I noticed was that both times it seemed to start heating up after instantiating iZotope Neutron. I realise Neutron is loading up multiple effects, but I've been using this a lot without any problems and with much larger sessions with convolution reverbs etc... 

 

Is this typical behaviour of a fan simply wearing out over time? or could Izotope Neutron or even Logic be somehow interfering and cutting off the fan? Is that even possible? Are there any other diagnostics I can do to help isolate the problem? I use the laptop daily for work so sending it into repair/maintenance is the last resort. Thanks in advance. 

Fans can drop out at low speed if they are worn out. There might be an obstacle or barrier at a certain rotational angle that stops the fan at low speed and prevents it from spinning up even when the voltage or PWM active cycle is increased. I don't think it's a software issue.

if you can somehow manage to run the computer with the back removed, you can observe what's going on. If the fan stops at some point and the heat increases again, try to give the fan blades a nudge in order to see if it will run again. If it does it is definitely worn out and needs to be replaced.

I should mention you have to be very careful while trying this, avoid touching anything inside but the fan, don't use too much force and avoid short circuits by metal tools... It's on your own risk.

It sounds to me like you need to have the unit checked-over at a service shop ... very soon!  

Fans can drop out at low speed if they are worn out. There might be an obstacle or barrier at a certain rotational angle that stops the fan at low speed and prevents it from spinning up even when the voltage or PWM active cycle is increased. I don't think it's a software issue.

if you can somehow manage to run the computer with the back removed, you can observe what's going on. If the fan stops at some point and the heat increases again, try to give the fan blades a nudge in order to see if it will run again. If it does it is definitely worn out and needs to be replaced.

I should mention you have to be very careful while trying this, avoid touching anything inside but the fan, don't use too much force and avoid short circuits by metal tools... It's on your own risk.

Thanks. I started it up with the back plate off just to see if the fan was actually moving (which is was), but I couldn't really work out a way to put it into use safely and see the screen properly. I was a bit nervous about dropping the laptop or getting fried. I was hoping for some kind of diagnostics software that gives more information than simply if the fan is running or not and the RPM. I suppose I'll try and replace the fan as a first step. Cheers.

Fans can drop out at low speed if they are worn out. There might be an obstacle or barrier at a certain rotational angle that stops the fan at low speed and prevents it from spinning up even when the voltage or PWM active cycle is increased. I don't think it's a software issue.

if you can somehow manage to run the computer with the back removed, you can observe what's going on. If the fan stops at some point and the heat increases again, try to give the fan blades a nudge in order to see if it will run again. If it does it is definitely worn out and needs to be replaced.

I should mention you have to be very careful while trying this, avoid touching anything inside but the fan, don't use too much force and avoid short circuits by metal tools... It's on your own risk.

Thanks. I started it up with the back plate off just to see if the fan was actually moving (which is was), but I couldn't really work out a way to put it into use safely and see the screen properly. I was a bit nervous about dropping the laptop or getting fried. I was hoping for some kind of diagnostics software that gives more information than simply if the fan is running or not and the RPM. I suppose I'll try and replace the fan as a first step. Cheers.

Check out iStat Pro.  here! 

I've been monitoring CPU temperatures and fan speed while doing various CPU intensive tasks (thanks to cleamon for recommending iStat - it's great). Turns out my fan is shutting off once the temperature reaches about 70-80C (precisely when its needed). It's doing it with non-logic tasks like video too, so that eliminates my idea that it was an Izotope plugin that was somehow causing the fan to stop. So I guess the fan just needs replacing. 

Well, yes, you can try that... But it sounds quite absurd the fan stops running when high temperatures are detected. The fan doesn't know anything about temperatures, it is driven by a circuit on the mainboard that decides how fast the fan should be running, so I think some management chip/controller on the board is freaking out. Maybe resetting the SMC solves your problem, see https://support.apple.com/en-us/HT201295