Had a flat in a tube that contained Slime. The Slime didn't stop the leak because the hole was rather large. I put a rubber patch over the hole and pumped up the tire with a mini pump . After I removed the pump, air kept leaking out of the Schrader valve. Apparently Slime had clogged the valve open.
Decided to replace the Schrader tube with a brand new Slime tube with a Presta valve. Same problem while airing up the tube. Valve stuck slightly open and let all the air out.
Has anyone else had similar problems with valves sticking open from Slime?