thanks for info about upper intake manifold  on 3800 seriers 11  engine ... my 1995  pontiac bonneville  . developed  coolant leak  but not into oil  crankcase ..  removed both heads & had valves ground . new head gaskets & hoses replace  ..then  found out it was upper intake manifold  leakings /// total cost with me doing work was about  $660.00 dollars  .... if  i had your info before ... it would have save me about  $500.00 dollars.... ...pontiac bonneville is driven every day of the week..  as of now has  240 thousand miles on it .. so even with money spent .. not a bad engine .. thanks  GM ...