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A/C vacuum problem need advice

Discussion in 'General Discussion' started by Turbo Zach, Jun 17, 2017.

  1. Turbo Zach

    Turbo Zach G-Body Guru

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    I have developed a vacuum problem. I have a 3.8 turbo engine. I have had some issues with my vents changing from floor to dash vents. Last winter I changed my rearend gear ratio to 3:42. The vents change ok at idle or low rpm. When I am going above 60 mph I am not running very much vacuum, under 10 psi. Do to the higher rpm and turbo. My vents switch back to the floor. Do I need a check valve on my round ball or is this the nature of the beast? The car does not get drivin in cold. Is there a good way to lock it in dash vent position? What are your thoughts on this problem?
     
  2. Turbo Zach

    Turbo Zach G-Body Guru

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    No one has any thoughts on this? My cruise dose not work now in high speeds either.
     
  3. Texas82GP

    Texas82GP Comic Book Super Hero
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    Maybe start with making sure the system holds vacuum with a Mighty-Vac. I'm surprised that 10 in. hg. is insufficient to operate the dash vents. I guess you could take the dash vents and cruise off of manifold vacuum and run them of an electric or belt driven pump. Those are the only ideas that come to my mind.
     
  4. BOXCARS

    BOXCARS Apprentice

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    Yeah, you need a check valve. My car was doing the same thing and I changed a check valve close to the firewall where the vacuum lines go into behind the dash.
     
  5. Turbo Zach

    Turbo Zach G-Body Guru

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    Dose any one have a part number for the check valves?
     
  6. foxtrot

    foxtrot Royal Smart Person

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    I believe that I have a Dorman 47149 Vacuum Check Valve installed for my HVAC vacuum. It's installed right before the HVAC hard line under the hood.. Good luck.
     
  7. foxtrot

    foxtrot Royal Smart Person

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    I was mistaken with regards to the install location, it's installed on top of the intake in the vacuum line that feeds the HVAC vacuum ball.
     
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  8. BOXCARS

    BOXCARS Apprentice

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  9. airboatgreg

    airboatgreg Master Mechanic

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    Start with check valve. You may think about a larger vacuum reservoir. Find a central vacuum source on engine. Ford actually make a decent check valve
     
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  10. foxtrot

    foxtrot Royal Smart Person

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    What's the Ford part number for the check valve? Thx.
     
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