Hello . I'm back again after years of absolutely no problems with the truck . Vacuum pump went south along with drivers side head gasket . Replaced the gaskets and checked the heads for thru cracks and warp. All AOK . Test drove and it started to blow bubbles out the reservoir again . Ripped it apart again . No apparent damage to the gaskets best I could tell after dragging heads across the gaskets with the manifolds still attached while removing them . There are now gold outline of the intake valve deposits on the piston heads. What could this be from . Also has any not tried the copper tube trick between the intake and exhaust valve seats to cure the cracks between them .