Was looking under the hood today and noticed this tube that says vac but isn't hooked up to anything. It goes into the firewall. Anybody know what this is and what should be hooked up to it.
The a/c and heater are long gone and the only vents that work are the ones for the defroster. A mechanic told me another cable under the hood that was cut was for the cruise control and that cable looks like a pic of a cruise control cable. Hopefully that makes sense
The vacuum line is to provide vacuum to the cruise control actuator so it can pull on the cable, not to tell it when the brakes are applied - that's done by an electrical switch on the pedal. Vacuum (the reduced in pressure in the intake manifold relative to the atmosphere) changes with throttle position, not braking. The power brakes just have a vacuum-actuated booster; vacuum's doing the same thing in both cases there - providing force to power something. Regardless, if you don't need the cruise control, no need to worry about it.
^you sure that's correct? When I pulled mine out of the fender the other end was hooked up to a mini box pump coming off the brake pedal. When you depress the pedal it would actuate a small plastic arm pumping air to that. Would make sense that it provided signal to disengage the CC.
OK, I double-checked in the service manual and there is a redundant safety system I'd forgotten about. My description above is correct, so far as it goes, and the vacuum line under the hood that he was asking about is the one that would normally go to the distribution manifold on the firewall and provide vacuum to the speed control actuator.
However, there is also a mechanical vacuum dump valve on the brake pedal as a fail-safe. The brake light switch should deactivate the speed control electronically (as does a clutch switch), but in case that were to fail for some reason, there's also a mechanical vacuum dump valve on the pedal that will release the vacuum from the speed control actuator servo motor, mechanically releasing the throttle regardless of what the speed control computer is telling the actuator to do. That's the second vacuum line you saw going into the car.