NO, this is a residual pressure valve in the link, not what you need, or want on a road car.
All these do is let most of the pressure out back down the pipes after you have applied the brakes, but not all, it keeps a very small amount there to minimise brake pedal travel etc.
The valve you want is it near the rear wheels like a cylinder, not uncommon for these to leak, any rear disc equiped sierra one should be ok.
tabetha