"Suction Noise"

Discussion in 'General Ranchero Help' started by Matt Winters, Jan 23, 2020.

  1. Matt Winters

    Matt Winters In First Gear

    Messages:
    15
    I recently started working on a 1976 Ford Ranchero GT. She's got the 351 Windsor and the C6, as well a 4.56 posi rear end my grandfather put in it. It then sat for 25 years. There is a suction type noise that can be heard when you are inside. It sounds like it is coming from the dash/firewall area. Any suggestions on what it could be?
     
  2. Boiler92

    Boiler92 In Third Gear

    Messages:
    126
    Location:
    Indiana
    Air door vacuum leak?

    Our jobs going to Mexico?
     
  3. 72GTVA

    72GTVA Administrator Staff Member

    Messages:
    9,755
    Location:
    Chesapeake, VA
    On the left side, right side or center of the dash?

    Two Possible culprits: The easy one - does it have the vacuum actuated parking brake release? (This isn't too common but possible).

    The multi-point one: Heater/A/C/Defrost controls are controlled by vacuum, if the noise is to the left, check for a loose or missing hose set connection at the heater A/C control panel, if the noise is to the center look for a detached or leaking hose at the air conditioning plenum in the vicinity of the ash tray, if the noise is to the right look for detached or leaking hose at the control motor vicinity of the right kick panel.

    Does the noise change or stop if you change the position of the heater/A/C control?
     
  4. Matt Winters

    Matt Winters In First Gear

    Messages:
    15
    Hmm. Well, the car is unfortunately 3 hours away on a farm, so I cannot check immediately. However, if I recall correctly, it is on the driver side, or center. Thank you for the help. I appreciate it. How could I check if it has the vacuum operated brake release?
     
  5. 72GTVA

    72GTVA Administrator Staff Member

    Messages:
    9,755
    Location:
    Chesapeake, VA
    Inspect your parking brake assembly to verify that it does or doesn't look like the one HuevosRanchero refurbished for his car as detailed in this post (click to expand and then click on the photos and you'll find one that shows the vacuum motor you are looking for):

    Otherwise, it is likely a dislodged vacuum hose group that has come loose from the heater/A/C control panel.
     
  6. 65restomod

    65restomod In Overdrive BRONZE MEMBER

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    674
    Location:
    Danville,VT left NJ forever
    In very rare cases a bad vacuum brake booster leaking
     
  7. 72GTVA

    72GTVA Administrator Staff Member

    Messages:
    9,755
    Location:
    Chesapeake, VA
    That is a good one to check out as well, does the sound change when stepping on the brake?
     
  8. Matt Winters

    Matt Winters In First Gear

    Messages:
    15
    I do not recall. The brakes are really not functional. Only one works: the rear passenger side. It was also the only one we could successfully bleed. I think it is probably the AC line or parking brake release though. The noise it really only audible inside the car.
     
  9. Matt Winters

    Matt Winters In First Gear

    Messages:
    15
    Is the dislodged hose easy to fix? Or will I have to disassemble the dash to get to it? My grandfather tried to test the heater and the switch broke so now the fan is stuck on. Lol. So if it is near there, I'll probably fox it when I fix that.
     
  10. 72GTVA

    72GTVA Administrator Staff Member

    Messages:
    9,755
    Location:
    Chesapeake, VA
    Space in that area is limited, however you can reach up and locate the hose group perhaps. Access is a little easier if you remove the instrument cluster. The control unit removed looks like this:
    iu-4.jpeg

    The vacuum control manifold looks like this:

    s-l300.jpg

    And the vacuum hose group looks very similar to this (this is from a Crown Victoria, not a Ranchero/Torino but it is similar):

    iu-5.jpeg

    On the Ranchero/Torino hose group there are metal clips that help the hose group remain attached to the control panel. If that is where your leak is it could be the hose group molded connector may have come loose, or you may have a split hose, or the vacuum line from the engine may have come off, or the manifold (center picture) may have a crack and will require replacement.

    It is possible to remove the screws holding the control panel in the dash and work it out and pull it down to below the dash to work on it. While it is doable, be warned that it is an exercise in frustration with some dirty words and scratched hands almost an absolute guarantee.

    Check the brake booster first, then move on to audible detection of the area of the vacuum leak to isolate location, and then work that area. It is probably something simple, but we have had a fairly recent group of failures of that manifold on top of the control panel. People have found new manifolds to resolve that issue.
     
  11. 72GTVA

    72GTVA Administrator Staff Member

    Messages:
    9,755
    Location:
    Chesapeake, VA
    The fan in these will always be on if the mode control is moved from the "OFF" position, even if the fan switch is all the way to the left, the fan blows (that is the low setting).
     
  12. Matt Winters

    Matt Winters In First Gear

    Messages:
    15
    Thank you so much! What is the best way to test the brake booster?
     
  13. Matt Winters

    Matt Winters In First Gear

    Messages:
    15
    Yea. It was off, the he "tested it" and it broke in the defrost position. I wouldn't mind, but the fan squeals super loudly.
     
  14. 72GTVA

    72GTVA Administrator Staff Member

    Messages:
    9,755
    Location:
    Chesapeake, VA
    Start the car, listen for the "suction noise", step on brake pedal - it should change. Or start car and stick your head under the dash near the brake pedal and see if you can determine if the suction noise is from the firewall area or the dash.

    Without looking at it, would guess that he may have either removed the control lever from the manifold/switch assembly or broken the manifold/switch assembly. Afraid that you will just have to dig the control panel out of the dash to the point where you can inspect it.
     
  15. Matt Winters

    Matt Winters In First Gear

    Messages:
    15
    Yea, I'll probably pull the fuse for it for now. But eventually I'm probably going to have to pull the most of the dash apart. I have several guages that either don't work or work poorly. Probably just a matter of cleaning contacts. Unfortunately for me sitting for 25 years does some damage
     
  16. handy_andy_cv64

    handy_andy_cv64 In Maximum Overdrive SILVER MEMBER

    Messages:
    10,333
    Location:
    Seguin, TX
    Pulling the fuse won't stop the 'suction' sound; like looking for an engine noise, use a length of heater hose by starting the engine, put the hose to your ear, and use it to 'echolocate' the source.
     
  17. Matt Winters

    Matt Winters In First Gear

    Messages:
    15
    Let me clarify: I am going to pull the fuse to stop the fan from squealing. As of right now, the suction sound will have to wait until I rebuild all four brakes and suspension components, as well as a carburator.
     
  18. 1979 RANCHERO GT

    1979 RANCHERO GT In Overdrive

    Messages:
    952
    I doubt that many 72s if any had auto park brake release. The cars that have them do not have a handle that has "brake release" written on it. My thoughts are it is the heater control leaking. The instrument cluster voltage regulator (on the back of the cluster housing) could be some of the gauge problem. The gauge housings are very brittle and do not take much to break them and replacements are hard to find..
     
  19. handy_andy_cv64

    handy_andy_cv64 In Maximum Overdrive SILVER MEMBER

    Messages:
    10,333
    Location:
    Seguin, TX
    Ah, somehow I missed that. Nobody likes a squealer.
     
  20. LSChero

    LSChero In Maximum Overdrive PLATINUM MEMBER

    Messages:
    2,178
    Location:
    Area 6 NV
    Fan power runs off circuit breaker at fuse block.You can also unplug wires at blower motor or disconnect heater cable at box and move switch to off position.
     

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