Mac Pro 3,1 crashes during sleep with fans going high

I have a Mac Pro 3,1 that works fine, but since I have bought it used it tends to crash every few days with fans on high. I have not see anything reasonable in the logs.

SMC etc. all have been reset. This has been an issues since Mavericks with new installs, new disks etc. memory checks out ok. And it does not happen, while awake.

Any ideas?