MBP case temperature vs. internal temp

[ryanrul]

I am in the process of exchanging multiple MBPs because of the yellow tint issue and i've noticed that between the two units i've had so far iStat pro is only showing a slight difference in temperature at the CPU (about 5 degrees) and yet the difference in temperature of the case of the laptop is extreme. The first unit ran a little warm, but even when watching video didn't get excessively hot. The second unit is so hot i can barely touch it on the left side even when i'm just browsing the web and typing this message.

Running smcFanControl brought the temperature of the new MBP down to the same reasonable levels of the first MBP. But i'm still curious ... What factors could cause such a big difference in temperature on the outside of the unit when there doesn't seem to be much difference around the CPU?

thanks in advance

 

[Jurwin]

Excessive thermal paste...
That said my 2.5ghz mbp running many apps open never gets above 55*C.

 

[ryanrul]

Interesting.
This second MBP will get 5 degrees hotter than that when mostly idling.

Is there any danger in always upping the fan speed with smcFanControl? I've found that a small increase in fan speed can make a big difference in the temperature but i don't know whether the fans are built to e spinning at higher rpms all the time. Has anyone used smcFanControl consistently for a long time (ie: more than a year) and been able to see whether they run into problems down the road?