1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

vacuum brake booster

Discussion in '6.9L IH & 7.3L IDI Diesels' started by mexicanjoe, Oct 2, 2019.

  1. mexicanjoe

    mexicanjoe Full Access Member

    Posts:
    94
    Likes Received:
    34
    Joined:
    Aug 4, 2018
    Location:
    texas
    Is thee one standard sized vacuum brake booster for F-250 with 7.3 idi? I get about one good stop out of my '89 before the pedal starts stiffening. The master cylinder is new so Im think along the line of a new booster....... any ideas from the gallery??? su amigo: mexicanjoe
     
  2. dgr

    dgr Full Access Member

    Posts:
    713
    Likes Received:
    97
    Joined:
    Aug 5, 2012
    Location:
    sac town
    Run a vacuum hose into your cab and measure your vacuum whole using the brakes. I would lean towards the vacuum pump not doing it's job.
     
    RetiringColt likes this.
  3. Randy Bush

    Randy Bush Full Access Member

    Posts:
    389
    Likes Received:
    202
    Joined:
    Jan 2, 2019
    Location:
    Great Falls, Mt
    Second the pump getting bad or a vacuum leak.
     
  4. Selahdoor

    Selahdoor How can I help you, or make you laugh, today? Supporting Member

    Posts:
    608
    Likes Received:
    311
    Joined:
    Oct 26, 2015
    Location:
    Index Wa
    Have you checked for vacuum leaks already? If your vacuum reservoir looks anything like mine did, you have zero or almost zero vacuum, no matter what the pump produces.
     
    RetiringColt likes this.
  5. mexicanjoe

    mexicanjoe Full Access Member

    Posts:
    94
    Likes Received:
    34
    Joined:
    Aug 4, 2018
    Location:
    texas
    i have 22" of vacuum with the engine running. im thinking a vac cum leak somewhere... It it appears the vacuum booster is OEM from 1989 so theirs that.... I cant a leak but my question is this: should the booster/ vacuum system go to ZERO as soon as the engine is cut off? secondly , how do you check for vacuum leaks? using sudsy water perhaps?
     
  6. arizhntr

    arizhntr Registered User

    Posts:
    7
    Likes Received:
    4
    Joined:
    May 29, 2011
    Location:
    Tucson, Az
    It should hold vacuum for a while, a visual inspection of the lines is about the only way you can check, Unlike a gasser where you can locate a leak with ether. But the good news is there are only a few systems working with vacuum - cruise control, a/c and brake booster. Check the vacuum check valve at the booster - where the line hooks on. They are plastic and are prone to failure.
     
    DaveBen likes this.
  7. chillman88

    chillman88 Supporting Member Supporting Member

    Posts:
    2,851
    Likes Received:
    1,799
    Joined:
    Feb 22, 2017
    Location:
    Central NY
    I've also heard of the fitting on the firewall leaking.

    Inspect the fitting and grommet on the booster, then isolate the system. Run a clean vacuum line from the pump directly to the booster. That way if it doesn't leak it can't be the booster. Likewise, if it does leak still, it has to be either the pump or the booster.
     
    saburai and Selahdoor like this.
  8. dgr

    dgr Full Access Member

    Posts:
    713
    Likes Received:
    97
    Joined:
    Aug 5, 2012
    Location:
    sac town
    If you want to use soapy water you will need to apply low pressure to the vacuum lines
     
  9. Selahdoor

    Selahdoor How can I help you, or make you laugh, today? Supporting Member

    Posts:
    608
    Likes Received:
    311
    Joined:
    Oct 26, 2015
    Location:
    Index Wa
    You could take the line off of the vacuum pump.... Apply pressure instead of vacuum. (I wouldn't go above say ten to 20 pounds of pressure.) Then use soapy water to test all the lines and such.

    And you might be wasting your time if you don't locate the reservoir and test it as well..
     
  10. hallgren87idi

    hallgren87idi Full Access Member

    Age:
    26
    Posts:
    95
    Likes Received:
    1
    Joined:
    Jul 10, 2013
    Location:
    gold bar, washington
    I would check the vacuum pump, sounds like it may be weak.
     
  11. Oledirtypearl86

    Oledirtypearl86 Full Access Member

    Age:
    33
    Posts:
    1,084
    Likes Received:
    525
    Joined:
    Sep 17, 2018
    Location:
    Whitehall MT
    @mexicanjoe I use a mightyvac that has the pressure option to chase vacume leaks by testing seperate systems it take a little more time but makes it easier for me and even after finding 1 leak I continue through the whole vac system
     
    RetiringColt and mexicanjoe like this.
  12. Slicknik

    Slicknik Full Access Member

    Posts:
    104
    Likes Received:
    45
    Joined:
    Apr 5, 2019
    Location:
    Burbank, CA
    @mexicanjoe

    you say you have 22” at idle but what happens when you press and hold the brake pedal? How much do you loose?

    Your booster check valve could be faulty , your booster could also be failing
     
  13. mexicanjoe

    mexicanjoe Full Access Member

    Posts:
    94
    Likes Received:
    34
    Joined:
    Aug 4, 2018
    Location:
    texas
    Oledirtypearl 86 and Selahdoor seem to have the answer...Im gonna try both and wee what happens....Can getting a bigger booster improve pedal feel???
     
  14. Cubey

    Cubey Full Access Member

    Posts:
    1,146
    Likes Received:
    220
    Joined:
    Oct 18, 2017
    Location:
    USA
    My RV's booster was bad despite under 100k miles, so they can indeed go bad.
     
  15. Desertfireguy

    Desertfireguy Full Access Member

    Posts:
    66
    Likes Received:
    8
    Joined:
    Sep 30, 2014
    Location:
    Northeast Texas
    Check that coffee can ( Mine is behind the DS headlight on my 92), your manifold, and one way check valves. Cheap replacement. New vacuum lines aren't that expensive either. Think I bought a 25' spool of motorcraft line for not much of anything.
     
    RetiringColt and mexicanjoe like this.

Share This Page