this can either be your thermostat or the water pump is not moving enough water. Check the weep hole to see if you have any residue there. THe only other thing is maybe the fan clustch is having problems. If you drive it hard does the temp rise?
2005 320 CDI
2006.5 VW Jetta TDI
1991 560SEL (179000 Sold)
1972 280SEL 4.5 ('The Lead Sled' 320000 miles when sold.)
1972 220D (225000 when sold)