know what try this company Norwesco Industies in Edmonton 780-437-5440

 

http://www.foambymail.com/ lots of goodies here

 

If you can get an MSDS on the product it would be a good idea to check the max operating temp since it is going under the hood... what is the max expected temp under the hood? I would guess ~90 degrees C or say 180 F?
I think you are speaking of neoprene and it might be OK...
I am thinking of hitting mine with the truck bed liner spray (polyurea)

 

http://modena.intergate.ca/customgasket/elastome.htm
Link has a lot of thermal parameters of various rubber/silicon/neoprene materials.