I have a quick question. In troubleshooting my heating system I have had to find the vacuum lines that go into the heat control head unit and have started wondering about how the entire system works. Mainly my question is, how is vacuum is generated. is there a vacuum motor in our engine compartments and if so where. I traced one of the vacuum hoses all the way to the fron driver side and goes into some kind of a box. Is this where the vacuum comes from and if so how is vacuum generated. It's got to be connected to the motor somehow, right?. Well I can't figure how the setup might be. I've looked at the vacuum diagram in a Chilton manual and for my 91 305 tpi car there's only a few places where vacuum goes into. According to the diagram, vacuum is needed for the MAP sensor, EGR valve, heater control valve and of course to the controls of the heater control unit. I think there are other places where vacuum hoses go into but i can't remember which where them. Still, according to this diagram there aren't as many vacuum hoses as I though there would. Could somebody explain to me where is the vacuum generated and which sensors or systems are critical to have vacuum going into them

 

Vacuum is generated by the throttle restricting the amount of air that can go into the engine. Idle or light throttle = high vacuum, wide open throttle = low vacuum.

The MAP sensor tells the computer what the engine is doing. Everything else is tapping a "free" power source.

Two other things that use vacuum are the power brake booster and cruise control.

 

The little black box is a vacuum canister of sorts, it get it vacuum from the engine. The vacuum from the engine operates the whole system.

 

vacuum motor

I have 5 of those right now (in vehicles anyway).

A 305 in my '83 P/U
A 1.8L in my '04 Vibe
A 2.5L in my '93 MX6
A 350 in my '71 Camaro
A 305 in my '92 Camaro



I have 2 other 350s and a 400 waiting to be put together.

 

You must never drive a WOT