A8 coolant circulation issues @#$%^&* !!

[Bing]

I recently replaced the the timing belt,t-stat,water pump,rollers and what
not on my 98' A8 4.2Q  and now running hot at stop lights...I have cracked
the bleed valves at the heater core to release trapped air, but not much air
purged..My t-stat housing is super hot to the touch but my lower radiator
hose is ice cold from rad bottom to t-stat housing while upper hoses are
hot..T-stat is operational,it opened in pan of boiling water.....What
Gives???

-- 
Bing
'01 A4 2.8QM 30v
'98 A8 4.2Q
'93 ur//S4
82 valves :-)