Mrspencer

Not sure if I'm missing the other end or if gets capped off, can't find any loose lines is it supposed to be bare like it is Trying to still source the root of a stiff brake pedal. 85s3 5 spd.
also is there a test for the venturi that leads to the booster.

GT6ixer

My '84 is exactly the same. Looks like a pop rivet shoved in there just like yours.

mkriete

I believe that is a test port, and no line is missing.
I have a Tee on my '80. One goes to the brake booster, one to the cruise control, and one to the HVAC. The other end is a capped test port.

hacksaw

I have an 84. mine only has 3 lines with 4th plugged.

drscottsmith

Yes you are all correct. 4th port is a test port and should be plugged with what you see in mrspencer's pic.

-scott

Mikebte

correct, test port. I hook my mighty vac in this spot to test operation. very good spot. One line goes to vacuum canister, other tees into the dash for AC and I forget the location of the third. At least on my 80.

If you remove it you may go back with new rubber. On mine the old rubber would not hold the plug once I got it removed.