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Vaccum lines--where are they

mtnman210

mtnman210

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I have no idea when it comes to this, I'm trying to get the motor fired in on the project and still have to hook up the vacuum lines. How many are there and where are they/where do they go. it's the cad500 with a quadrajet on it, if that makes a difference.
 
I'm looking for the A/C and heater hose diagram, I can't get air from anywhere but the floor. Never any vacuum to the vac motor to close the door at the floor. I'm not sure if it's the switc or maybe even a broken hose somewhere. I just want to know where each hose goes from the switch.


And this is post number 100, do I get a prize? LOL
 
Sorry I can't really help on the specifics, but you likely have a vacuum storage container (typically a black, round plastic ball about 6"). Probably need to check that it's hooked up first, and that the supply line feeds your heater control head.

If it were me I'd probably plug every vacuum port there is (except what you KNOW gets hooked up and works, for instance the brake booster) and fire it up/break it in that way, then deal with the vacuum lines. Vacuum advance, modulator (if you have one) heater control, etc.
 
If you go to a large Public Library, they will have a section for automotive technical books. The books would be aranged by year for both domestic and import vehical. In the past I have found both wiring and vacuum diagrams. I realise that with the internet most people never visit the library. Make sure it is a large County library. I have found detailed information to rebuild engines, manual & automatic transmissions, and clutch repair. It is a nice place to visit.
 
mtnman210 said:
I have no idea when it comes to this, I'm trying to get the motor fired in on the project and still have to hook up the vacuum lines. How many are there and where are they/where do they go. it's the cad500 with a quadrajet on it, if that makes a difference.
Click to expand...

what year set up?

as mentioned you need full vacuum for your brakes, off the back of the carb, on the front side of the carb you have one that connects to your vacuum advance on the distributer, then one for the pcv.

you also may have one needed for your tranny that runs from carb


post up more info, year, trans, emissions stuff?
 
Now this is probably a dumb question, but where do the heater controls get their vacuum from?
 
jonathon said:
Now this is probably a dumb question, but where do the heater controls get their vacuum from?
Click to expand...


A/C & heater controls. They get their vacuum from a vacuum reservoir mounted under the master cylinder. The PO disconnected all the vacuum going to the controls and I'm trying to get the vacuum motors to work. He used cardboard in the heater vent to direct air flow to the dash vents.
 
supersize75k5 said:
what year set up?

as mentioned you need full vacuum for your brakes, off the back of the carb, on the front side of the carb you have one that connects to your vacuum advance on the distributer, then one for the pcv.

you also may have one needed for your tranny that runs from carb


post up more info, year, trans, emissions stuff?
Click to expand...

it's a 74 caddy 500 with an electric choke quadrajet and a th400 for a tranny. I have no heater/air or anything extra. There is nothing on the firewall except some wires and the fuse block going into the cab:D Also I have ZERO emissions stuff on this truck
 
then proceed as I mentioned,


3/8 full manifold vac to the brake booster
3/8 tot he pcv

the two small ones, one goes the the vacuum port on the tranny and the other to the dizzy
 
Hey folks, I have a similar vacuum question so I figured I'd piggyback (not hijack) it onto this thread. I have a 1991 blazer that has no heater controls, only getting slightly warm air out of the floor vent. The hot/cold mechanism on top of the heater box seems to be working. nothing looks broken. after reading some of the posts on here, I looked under the hood to check vacuum lines.

the line from the spherical reservoir is dry rotted, so that's not good. also, one of the lines going to the modulator (? - the device to the right of the distributor in this picture) is rotted. also, there is a smaller line that T's off of those lines that isn't attached to anything. it was hanging along the firewall. I pull it out for the picture. lastly, there's a device on the intake manifold to the left of the TBI that has a vacuum port with nothing attached. is this the PCV and should that empty line go to that, or should that one go to the tranny? all the hoses on the heater controls in the dash appear to be attached.

here are two pics, one with my notes, one without. feel free to use either for any future "this line goes here" reference post. (i tried to insert them as pics or links, but my noob status prevented it. maybe some other member can insert them for others to see.)

bloomautomatic(dot)com(slash)91k5vacuum(dot)jpg (with my notes)
bloomautomatic(dot)com(slash)91k5dist(dot)jpg (without)

thanks for your help. this is the first blazer i've owned.

Vince
 
British Slave said:
The hose to nowhere goes to the heater/AC control in the dash.
The rotted hose is on your cruise control, and since you have disconnected it you could plug those
Click to expand...


Thanks for the quick reply. Can you tell me about where the hose for the heater controls would go through the firewall?

Vince
 
British Slave said:
It's just out of the picture on the left. There should be a hard plastic line comming out of the grommet laft of the wiring harness going thru the firewall. Does your heater/AC work?
Click to expand...

Thanks again. The fan blows kinda warm air out of the floor vent only, no matter which vent the controls are set on. Haven't tried the A/C since it's winter here.
 
Success! I found the line coming out of the firewall and ran a new line to it. Works like a charm now. Took it for a drive, controls work and I'm getting heat.

Thanks for your help, British Slave!

Vince
 
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