How to clean sealant stuck in pump head? I have a old trusty pump that over the years has the presta head filled with tubeles goo. Noways it pumps the tires very slow. Is there any chemical way to remove it without melting the plastic?
You should be able to disassemble the pump head and clean out the blockage manually. 

I’d try 70% isopropyl alcohol as a solvent to help remove sealant.