MALIBU Location Vacuum Control Actuator

Ratchet

Greasemonkey
Jan 10, 2018
238
28
Where is the Vacuum Control Actuator located on my 80 Malibu, V6, w/AC? Here is a pic of the part.
 

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Ratchet

Greasemonkey
Thread starter
Jan 10, 2018
238
28
The only air that is coming out on my 80 Malibu is at the floor. The round disk at the dash control unit has been cleaned and inspected. It appears to be in useable condition. The under dash vacuum lines are in their correct locations. My guess is the problem lies in the engine compartment. Do you have any suggestions?
 

CopperNick

Royal Smart Person
Supporting Member
Feb 20, 2018
2,238
113
Canada
Couple of things here. First, the vacuum tank shown in the diagram is actually a globe or spherical plastic ball. The picture doesn't portray it all that well but if you look closely you can see the mounting tab peeking out from under the two air nipples shown.

Secondly, the picture you posted is, unless I am totally mistaken, which does happen at least once a minute, the actuator for a cruise control. On the motor, it is attached to a "Y" shaped bracket that bolts to one of the drilled and tapped 3/8ths NC holes located in the driver's side head and between it and the firewall. In the picture you can see the two mounting studs that attach it to the arms of the Y. The flat slide arm that protrudes from in between the studs is attached to a diaphragm that is inside the flying saucer shaped metal body. On the motor,. there is a short chain that runs from the end of the slide to a pivot point on the throttle lever on the carb or TBI.

As for your air flow issue, the diagram shows the upper and lower mode valves and, just a thought here, it could be one of them that has malfunctioned. There is also a flapper panel in the ducting that is mechanically adjusted by means of a lever/cable mechanism that is part of the control head. Using the lever to move the panel modifies the air flow from down low to the upper vents. On the control body it might show as a horizontal slot with a small knob sticking out of it. Sometimes the actuator cables jam or break.



Nick
 

Ratchet

Greasemonkey
Thread starter
Jan 10, 2018
238
28
Couple of things here. First, the vacuum tank shown in the diagram is actually a globe or spherical plastic ball. The picture doesn't portray it all that well but if you look closely you can see the mounting tab peeking out from under the two air nipples shown.

Secondly, the picture you posted is, unless I am totally mistaken, which does happen at least once a minute, the actuator for a cruise control. On the motor, it is attached to a "Y" shaped bracket that bolts to one of the drilled and tapped 3/8ths NC holes located in the driver's side head and between it and the firewall. In the picture you can see the two mounting studs that attach it to the arms of the Y. The flat slide arm that protrudes from in between the studs is attached to a diaphragm that is inside the flying saucer shaped metal body. On the motor,. there is a short chain that runs from the end of the slide to a pivot point on the throttle lever on the carb or TBI.

As for your air flow issue, the diagram shows the upper and lower mode valves and, just a thought here, it could be one of them that has malfunctioned. There is also a flapper panel in the ducting that is mechanically adjusted by means of a lever/cable mechanism that is part of the control head. Using the lever to move the panel modifies the air flow from down low to the upper vents. On the control body it might show as a horizontal slot with a small knob sticking out of it. Sometimes the actuator cables jam or break.



Nick
Actually, the photo above is off of Ebay. My car does not have Cruise Control.
 

CopperNick

Royal Smart Person
Supporting Member
Feb 20, 2018
2,238
113
Canada
Wee-elll, the caption on the sale picture does say that it is an A/C control vacuum actuator. And it does bear sort of a passing resemblance to the upper and lower modules shown in the diagram. Unhappily, the caption does not include the description of the part and its application with respect to year and make/model. If you suspect one of the vacuum modules to be your culprit, you are still going to have to invade the dash spaces behind the control head and see if the problem is obvious or if you are going to have to sweat for it.


Nick
 

Ratchet

Greasemonkey
Thread starter
Jan 10, 2018
238
28
There does not appear to be any obvious problems. Is there a was of testing the actuator(s)?
 

ELCAM

G-Body Guru
Jun 19, 2021
709
93
Out of the car, compress the diaphragm and put a finger over the vacuum nipple, if it stays compressed it is air tight.

On the car use a mightyvac and apply vacuum and see if the vacuum leaks down showing a leak `in the diaphragm.
 
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Ratchet

Greasemonkey
Thread starter
Jan 10, 2018
238
28
Out of the car, compress the diaphragm and put a finger over the vacuum nipple, if it stays compressed it is air tight.

On the car use a mightyvac and apply vacuum and see if the vacuum leaks down showing a leak `in the diaphragm.
Thanks
 

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