2011 iMac Reboot Loop

[pricklypete]

I'm hoping someone can offer me some advice on a problem I'm having with a 2011 27" iMac.

I bought the machine with video not working. I replaced the video card, and installed an SSD, and the machine seemed to be working fine for a couple of days.

I started to notice that the fan seemed to always be blowing, so I took it apart again and put some new thermal paste on the processor (Artic MX-4). Now, I'm in a constant boot loop- sometimes I will get to the login screen followed by an immediate reboot, sometimes it will reboot before it gets there. The fans run normally throughout the process, not blowing hard.

I'm not sure if this latest problem is a direct result of the work I did with the thermal paste, or just a coincidence. It seems that if it were a thermal issue it would take longer to overheat before a reboot?

Can anyone give any suggestions on anything I could check that could be causing this? Thanks for looking!

 

[pricklypete]

I'm hoping someone can offer me some advice on a problem I'm having with a 2011 27" iMac.

I bought the machine with video not working. I replaced the video card, and installed an SSD, and the machine seemed to be working fine for a couple of days.

I started to notice that the fan seemed to always be blowing, so I took it apart again and put some new thermal paste on the processor (Artic MX-4). Now, I'm in a constant boot loop- sometimes I will get to the login screen followed by an immediate reboot, sometimes it will reboot before it gets there. The fans run normally throughout the process, not blowing hard.

I'm not sure if this latest problem is a direct result of the work I did with the thermal paste, or just a coincidence. It seems that if it were a thermal issue it would take longer to overheat before a reboot?

Can anyone give any suggestions on anything I could check that could be causing this? Thanks for looking!

[doublepost=1557343890][/doublepost]After reading some more, this may be another video card crapping out (seems to be very common for this model year). I'm going to boot in verbose mode to see if I get any messages indicating video bombing.

 

[AlaskaMoose]

[doublepost=1557343890][/doublepost]After reading some more, this may be another video card crapping out (seems to be very common for this model year). I'm going to boot in verbose mode to see if I get any messages indicating video bombing.

I replaced the SSD on my 2011 iMac. On this one there are two ways to control the hard drive fan speed after removing the har drive, since the SSD does not have a temperature sensor:

a. You can use one of several apps to control the fan speed
b. A temperature sensor and wire harness (a kit)

I used the app to control the fan (s) speeds while I waited for the sensor kit to arrive, then opened the iMac again and installed the sensor (problem solved)
https://eshop.macsales.com/item/OWC/DIDIMACHDD11/

I have never had a video card problem with mine.