Vacuum pump question

Discussion in '6.9L IH & 7.3L IDI Diesels' started by mexicanjoe, Dec 7, 2018.

  1. mexicanjoe

    mexicanjoe Registered User

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    i used a vacuum gauge to measure my 89 7.3 n/a pump. Turns out it topped (bottomed) out at 22" of vacuum. Is this sufficient for this unit? The reason I ask is because I can get 2 good stops on my brakes before it starts to get difficult to depress the brake pedal again. New master cylinder/brake booster , or is this normal? I have everything to do a rear brake job in the future including springs..... let me know your thoughts....... su amigo:
    mexicanjoe!
     
  2. riphip

    riphip Supporting Member Supporting Member

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    Joe, do you have someone that can press the brake pedal 3-4 times and hold while you check the vacuum?
     
  3. austin92

    austin92 Full Access Member

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    Did you check right off the pump or at the brake booster? Was the needle jumping on your gauge or steady?


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  4. mexicanjoe

    mexicanjoe Registered User

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    I checked it with engine running at the firewall. And if held the vacuum for several minutes afterward...
     
  5. austin92

    austin92 Full Access Member

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    You could check it at the booster and see if there’s a leak between it and the firewall. Does all your vents change ok and cruise work?


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  6. Macrobb

    Macrobb Full Access Member

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    Probably the pump can make vacuum, just not move a high volume of air(needed to "recover" the vacuum quickly) anymore.

    I'll bet it's the vacuum pump being fairly worn and the reed valves inside it not sealing correctly.
     
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  7. mexicanjoe

    mexicanjoe Registered User

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    All the vents work, the cruise does not. I have to find an adapter to check the booster though
     
  8. Oledirtypearl86

    Oledirtypearl86 Full Access Member

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    I'm with @Macrobb I. Think the vac pump is in failur mode if you are unable to maintain enough vacuum during high demand kind of like a small air compressor you can run that 3/4 inpact gun just fine but you. Loose all your power fairly quickly but give it a few and it's right back to full power
     
  9. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    Good description.
     

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