Hi, I have a 1982 Recaro T/A (WS6, 4 wheel disc brakes) and recently discovered a leak coming from the bottom port of the original proportioning valve. I decided to have the local GM dealer replace the valve with an aftermarket one I purchased, but after just a few short drives, I noticed that the aftermarket valve is leaking as well. The aftermarket valve does not have the lower port (as the original one does), but instead, has one on the upper part from which brake fluid is leaking at an even greater rate than before. (See photo of leaking port.) I am not a mechanic, but guessing that these ports serve the same purpose; just in different locations on the valve.

What could be causing both the original and aftermarket valves to leak? Is there some other problem in the brake system that I should consider?

Thanks in advance.