Slimy water pump

Hey guys, just did a water pump, thermostat, air pump delete on an 87 Econoline 460 R.V. all looked
Good till I removed the water pump. Surface of the block area was kinda slimy. No water in the oil and did a pressure test after all was replaced. Anybody ever experienced something like this? Also what’s everybody’s preference on thermostats, had a 195 in it and I replaced with a 180. Was at A on Normal when running and never seemed to move, now it’s at O and moves up and down with opening of the thermostat. Thanks for the help!!

Sounds like someone at some point in time put that liquid "stop leak" stuff in there. You may want to flush the radiator out as good as you can too!!