Vaccuum Hoses should not leak!!

Discussion in ''How To' & 'Handy Hints'' started by torquenut, Jan 28, 2008.

  1. torquenut

    torquenut New Member

    Messages:
    16
    Have had the 74 bus for 15 years. Recently noticed a lot of backfiring, and my brakes were fading. Basically needed to replace the master cylinder, (another story) and spent some time checking hoses and the One Way valve near the firewall.

    Those old hard plastic hoses have gotta go. I disconnected the vaccuum hose at the booster, and blew down the hose, (clean it first). You should have airflow in this direction. Then carefully apply vaccuum to the line. It can taste a bit yuck. If you have any leaks you can hear it. Basically you should not have any pressure loss at all. I had air going everywhere.

    So down to the hydraulics shop for 2 metres of 10mm air line, and a quick visit to our mechanic for a new one way valve (ours was not).

    This is a simple job, you remove your old hard non-sealing hoses, measure them against your flash new hose, add an extra 15-30mmfor good measure, cut and refit with new hose clamps.

    My brakes are excellent, and the backfiring has stopped, now just a low grumble during decelleration.
     
  2. Schmoburger

    Schmoburger Active Member

    Messages:
    4,431
    Location:
    Nowra/Jervis Bay area, NSW.
    Good post... the booster lines are a facet that are often overlooked when it comes to troubleshooting a rough running engine.

    I am even guilty of forgetting about em myself. Drove home on effectively 2 cylinders about a year ago after the left ahnd brake booster hose came off the manifold and escaped my attention. A leaky tract of hose as you found out, has similar effects. :)
     
  3. syncro

    syncro Well-Known Member

    Messages:
    8,526
    Location:
    Southern Highlands
    You should not use a pressure hose for vacuum.
    I know of a few cases of bad brakes due to the hose collapsing.
    Very common problem.
     
  4. torquenut

    torquenut New Member

    Messages:
    16
    Thanks for that, will keep an eye on it. The hoses we used are pretty thick, about 6mm, heavy duty.
    Another neat fix it is to check the vaccuum elbows on either side of the manifold, as thse rubber elbows are subjected to intense vibration and heat. They breakdown over the years but often are not noticed. Get your head in there with a torch.
     
  5. emby

    emby Active Member

    Messages:
    2,018
    Location:
    Wights Mountain, QLD
    I'm having issues with my elbows (the ones on the brake booster line, not the ones half way between my wrists and my shoulders). I've got some new ones as the ones in the bus at the moment are showing distinct sinzes of cracking, although not yet leaking. They're also very flexible, unlike the new ones I got from Roy.

    My problem is getting the little bleeders off. Has anyone got any tips on what to do or, more importantly, what not to do? If I pull on them, trying to loosen them of the brake booster line, the booster line is moving. I'm scared of causing damage here. Is the safest method just to take a stanley knife to the old elbows? Also, do you need to put any sealant on to ensure that there are no air gaps?
     
  6. emby

    emby Active Member

    Messages:
    2,018
    Location:
    Wights Mountain, QLD
    Thanks. It's better to make sure before I do something stupid :eek:
     
  7. Van Housing

    Van Housing Well-Known Member

    Messages:
    10,414
    Location:
    Williamstown Vic
    This thread would be better with photos! I should get the camera out, as this is a common issue that is easily solved. (unless someone else wants to do it, hint hint...)
     
  8. emby

    emby Active Member

    Messages:
    2,018
    Location:
    Wights Mountain, QLD
    OK.

    Hint taken Woz.

    Here's the vacuum lines with the air filter removed
    [​IMG]


    Left hand brake booster elbow in the centre coming off the inlet manifold and onto the brake booster line
    [​IMG]

    Right hand brake booster elbow...looks fine doesn't it?
    [​IMG]

    A little cut here, vertically, made it easier to peel off without leaving anything stuck to the booster line
    [​IMG]
     
    Last edited: Mar 22, 2010
  9. emby

    emby Active Member

    Messages:
    2,018
    Location:
    Wights Mountain, QLD
    Getting the elbow off the inlet manifold was a bugger. Must have been the heat from the manifold that gave it a nice seal.

    This is that booster elbow that looked fine....
    [​IMG]

    Check out all those hairline cracks :eek:

    New ones pushed on very easily.

    Other vacuum lines....

    The one from the preheater that goes to the air filter
    [​IMG]

    This hose, I'm lead to believe from Bentley, goes on to the brass connector on the "pizza" piece of the right hand side of the air filter....

    ....this one here
    [​IMG]
     
  10. emby

    emby Active Member

    Messages:
    2,018
    Location:
    Wights Mountain, QLD
    Finally underside....

    voila

    [​IMG]

    I think that other spigot connects to the central idling circuit. You can see it on this photo, centre / bottom, but mines plugged at the moment. had a hose there but it was old and cracked and haven't received my new hoses yet.
    [​IMG]

    And, yes I know, the main line coming off the left hand carby into the idle circuit is a brake line. This has been on it since I got the bus back. I'm currently trying to source a new piece of cloth braided pipe that's the righ size. If anyone knows of any please give me a nod. Cheers.


    Was that enough photos Woz or would you like some more?:lol:
     
    Last edited: Mar 22, 2010
  11. Van Housing

    Van Housing Well-Known Member

    Messages:
    10,414
    Location:
    Williamstown Vic
    Thanks heaps for that Matt - I don't have an overhead engine hatch anyway, so I could never have matched your quality. :)


    I'll add one pic though - the brake booster, underneath the front, which if disconnected will affect engine power as well as braking.
    [​IMG]
     
  12. emby

    emby Active Member

    Messages:
    2,018
    Location:
    Wights Mountain, QLD
    Cheers Woz...that was the one I forgot to take....

    Are you showing the line off on purpose...or is that how you found it when you took the photo? :lol:

    (P.S. love the overhead engine hatch...makes working on it so much easier)
     
  13. BrianK

    BrianK Well-Known Member

    Messages:
    7,158
    Location:
    Mount Gambier, SA


    Just looking at that picture, i would hope you found it off.:lol: It would be a worry if you took it off.:)
     
  14. Van Housing

    Van Housing Well-Known Member

    Messages:
    10,414
    Location:
    Williamstown Vic
    It was already off when I took the picture!
     
  15. Paul Lawler

    Paul Lawler New Member

    Messages:
    10
    Location:
    Hobart
    Hi Can you advise where you can buy the elbows from The bus Stop doesn't supply.

    Regards
    Paul
     
  16. 75SC

    75SC New Member

    Messages:
    29
    Location:
    Perth
    so.... I don't have any of those vacuum lines connected? both ones coming off the air filter are blocked off?
    I have dual carb with vacuum advance. any ideas?
     
  17. splitbus

    splitbus Well-Known Member

    Messages:
    3,254
    Location:
    Brisbane

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