260z rear brake issue | The Z Club of Great Britain
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260z rear brake issue

Discussion in 'S30 (240Z,260Z,280Z) Suspension,Brakes and Steerin' started by Peato40, Jan 29, 2018.

  1. Peato40

    Peato40
    Z Club Member

    Hello All,

    With my ongoing restoration of a 260z 2+2 I turned my attention to bleeding the brakes yesterday. Everything is new with the exception of the warning switch and proportional valve.
    Front brakes bled up nicely, but I wasn't getting anything at the rears. I followed some advice online about first bleeding the master cylinder, which seemed to be successful.
    So I disconnected the hard line going into the proportional valve and immediately found oil, so connected it back up again. I then disconnected the outlet of the valve and found it to be dry. At this point I decided to take a look inside, so dismounted the valve and opened it up and found everything to appear in good order, however I was struggling to understand exactly how it should work. It seemed to me that there needed to be pressure in the front line to then allow passage of oil to the rears but then this doesn't make sense if there was a front pressure failure because rear would then the be lost also.

    Is there a trick I'm missing here?

    Another option I have is the bypass the valve for the front and then put in a new adjustable valve in the rear line, which I guess I will need when I eventually get around to rear disc conversion.
     
  2. Stockdale

    Stockdale
    Z Club Member


    Bear in mind that on the 260z front and rear brakes operate through a tandem master cylinder (a safety feature) with seperate front and rear circuits.
     
  3. moggy240

    moggy240 INSURANCE VALUATIONS OFFICER Committee Member

    When I had trouble bleeding the brakes on my car I borrowed a brake suction device.
    It has a hose that fits over the loosened bleed nipper and then using a compressor connected to the device it sucks the brake fluid through so that you can finish bleeding it
     
  4. moggy240

    moggy240 INSURANCE VALUATIONS OFFICER Committee Member

  5. Peato40

    Peato40
    Z Club Member

    Hello All,

    Thanks for the feedback. I have a manual version (hand pump) of that device you describe moggy240, but it's not pulling oil through to the rear brakes ..... worked fine on the front.

    I just don't seem to be getting oil past the proportional valve for the rear circuit.
     
  6. Rob Gaskin

    Rob Gaskin Membership Secretary Staff Member Committee Member

    Phil, you are def talking about the proportioning valve are you and not the imbalance warning switch unit?

    Is your system like this (but RHD):

    Also have a read of this (but it's not your specific problem):

    http://zclub.net/forum/showthread.php?t=26205

    My first reaction would be to make absolutely sure that the rear system in the master cylinder has no air in it. I know you have bled it sorry but double check.

    Any pics of the proportioning valve apart?
     

    Attached Files:

  7. Peato40

    Peato40
    Z Club Member

    Hello Rob,

    Yes definitely the proportioning valve. Attached are some photo's of my set up, which showing how I bled the master cylinder and then the problem I'm having. I have oil flowing from port F to port F, which is the front line circuit and then I have oil flowing up to the port with the in arrow but nothing coming out of the out arrow port, if that makes sense?
     

    Attached Files:

  8. Rob Gaskin

    Rob Gaskin Membership Secretary Staff Member Committee Member

    Ok great. The car looks really nice by the way (and the wiring mods).

    If it was a function of the valve i.e. requiring front pressure it would have worked when all connected I assume.

    I'm thinking it must be the valve?
     
  9. Nigel Brook

    Nigel Brook Active Forum User

    Maybe the way I'm looking at the pics but the bottom pipe on the front connection (warning light unit) seems to be connected to the rear connection on the master cylinder. Is this correct?
     
  10. Albrecht

    Albrecht Active Forum User

    Peato40,
    Have you got a copy of he Nissan factory service manual for your car?

    If you haven't, there's a very good section in the UK & European 260Z manual covering the front and rear brake systems, including explanations of how the NP Valve, Proportioning Valve and Brake Pressure Differential Warning Light Switch work, as well as operating tests which can help you isolate and diagnose problems.

    It also points out that the NP valves are different for the 2-seater and 2/2 models, which is worth knowing.

    If you haven't got a copy, I could scan it up for you.
     
  11. Rob Gaskin

    Rob Gaskin Membership Secretary Staff Member Committee Member

    It looks ok to me Nigel.
     
  12. Peato40

    Peato40
    Z Club Member

     
  13. Peato40

    Peato40
    Z Club Member

    No I don't have a copy of the factory service manual Albrecht, so would very much appreciate a scanned copy if you don't mind.
     
  14. Albrecht

    Albrecht Active Forum User

    I can't scan the whole manual!

    I'm offering to scan the relevant pages in the Brake section, OK?
     
  15. Rob Gaskin

    Rob Gaskin Membership Secretary Staff Member Committee Member

    That's what I have but I do have rear discs.

    I think the fault with the valve is worth investigating one more time.
     
  16. Peato40

    Peato40
    Z Club Member

    Perfect ... yes please.
     
  17. Peato40

    Peato40
    Z Club Member

    Agreed, will be nice to get the entire system first working as intended, so I'll investigate it a bit further.:thumbs:
     
  18. Albrecht

    Albrecht Active Forum User

    Phew. Didn't fancy the idea of scanning the whole thing...

    My turn to cook dinner tonight, so I'll do it later and post up here.
     
  19. Peato40

    Peato40
    Z Club Member

    Thanks Albrecht,
     
  20. Albrecht

    Albrecht Active Forum User

    Scanner refuses to play ball, so I photographed a couple of relevant pages and put them on Imageshack:

    [​IMG][​IMG]

    [​IMG]

    [​IMG]
     

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