What is the black box on the passanger side of my firewall. it has a knob on the top that you can turn. its on a 90 5.0
is this a brake proportioning adjuster?
If you're referring to a part located on the back of the passenger side shock tower vs. the firewall and it has a 2 wire plug in as well as a couple of vacuum lines going to it, that is the e.v.r. ( e.g.r. vacuum regulator)
Held down by 2 bolts as well. The top is supposed to turn too.
Absolutely nothing. Its designed to act as a vent and release pressure when necessary, therefore the cap has to be slightly loose. You didn't damage anything if thats what you mean. In fact, the cap can be popped off too if you really want to see what it looks like.
No i dont have rear disc. i dont think its a brake regulator. but the brake lines do run right under it. but i can exactly see whats going into it cause of my a/c lines