1983 S-10 blazer porportional brake valve
 

I am having a problem with my porportional valve leaking fluid. The part is no longer made and I have installed 2 from a salvage yard that leak also. Any ideas on what is causing this? This is my 4 wheel drive for the winter and its not far from snowing here. Any help would be great

I think you can buy them new from LMC Truck, but they aren't cheap. I believe yiu're referring to the combination valve? I don't know for sure about an 83 but that's what my 84 has.