After numerous calls to Newell today I got my leak fixed (I think)! It turned out to be the stop valves. Had some scale deposits in them. I took them apart and soaked for +/- 1 hr in CLR. Rinsed them & wiped clean. Next step was high temp stem grease for reassembly. I did not change "o" rings, I left the old ones in place as they did not seem to be cut or scuffed on visual inspection. Plan "B" was to buy new assemblies from Grohe. My main problem was having a REALLY old Grohe valve. Dwight at Newell finally remembered the old ones made with brass instead of plastic. Followed his instructions to get it apart. If anyone needs help with these older valves drop me a note & I will be glad to try & talk you through it.