Comment 38 for bug 213818

Ok , I just realized that by setting the fan to "disengaged" makes it spin with up to ~4500 RPM after a minute or so. I'm pretty sure it never reaches that speed when its controlled automatically.
This is probably the problem: When controlled automatically, the fan is never disengaged, and does not even reach its full controlled speed of 3800 RPM, even when the CPUs are already overheating.
I think keeping the fan disengaged manually (echo "level disengaged" > /proc/acpi/ibm/fan) should prevent any overheating problems for the time being. Lets hope this gets fixed soon.