Exact same thing happened to me (in my oil leak thread). Turns out I was an idiot and had the breather tube disconnected and the crankcase pressure was building up (causing the abnormal heating, although mine never reached 100) and oil being forced up from the air filter/oil separator oil drain tube. I hope that's all it is for you.

Alex

__________________
1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside