It seems that you all are zeroing in on the problem. I had a lot of difficulty with the new replacement Teflon washers that seal the flow valve on the back of the group. The new replacement spec for model 85 did not fit the model 80 as well as the old ones...a different shape as the originals were slightly cupped and the new were kinof stepped. I too had to fiddle and tighten until I got a good seal but he metal rod goes through the Teflon seal while the nut hold the seal down and is supposed to squeeze it against the shaft. I think I ended up making a seal using sheet Teflon and center punches. The old way was to use strong and pipe dope...Teflon is cleaner but pretty fiddly.