Try this on your C5 and let me know the results
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  1. #1
    Fellow Frogger! dieselman's Avatar
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    Default Try this on your C5 and let me know the results

    1) Start the engine.
    2) Push hard on the brake pedal and hold the pressure for 15 - 20 seconds.

    Does your pedal slowly sink to the floor?
    Does it eventually reach the floor?

    I had my brakes bled by a Citroen dealer (including the ABS), but the pedal will still sink to the floor (eventually).
    The dealer assured me that all C5's exhibit this behavior. I'm not convinced, so please help to prove them right.

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    I am thinking the master cylinder seals must be allowing the fluid to leak back.

    Thanks.
    Leon

    1987 Peugeot 505 GTD
    2010 Citroen C5 3.0 V6 HDi
    2010 Citroen C5 3.0 V6 HDi (wife's car)

  2. #2
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    Mmm. ABS brakes have a very different feel to older power assisted brakes for example. First time I drove one I thought the brakes were faulty.

  3. #3
    Fellow Frogger
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    I think that is actually normal behaviour for the C5 and will eventually happen if you stand on the brake pedal for some time. I can't see why the dealer would tell you it's normal if it isn't normal in their experience. Do they stop the car correctly?

  4. #4
    Fellow Frogger! dieselman's Avatar
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    Default Re: Try this on your C5 and let me know the results

    Yes, the brakes stop the car quite well.
    Leon

    1987 Peugeot 505 GTD
    2010 Citroen C5 3.0 V6 HDi
    2010 Citroen C5 3.0 V6 HDi (wife's car)

  5. #5
    Fellow Frogger! dieselman's Avatar
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    Default Re: Try this on your C5 and let me know the results

    Nobody game enough to try this?
    Leon

    1987 Peugeot 505 GTD
    2010 Citroen C5 3.0 V6 HDi
    2010 Citroen C5 3.0 V6 HDi (wife's car)

  6. #6
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    Quote Originally Posted by dieselman View Post
    1) Start the engine.
    2) Push hard on the brake pedal and hold the pressure for 15 - 20 seconds.

    Does your pedal slowly sink to the floor?
    Does it eventually reach the floor?

    I had my brakes bled by a Citroen dealer (including the ABS), but the pedal will still sink to the floor (eventually).
    The dealer assured me that all C5's exhibit this behavior. I'm not convinced, so please help to prove them right.

    I am thinking the master cylinder seals must be allowing the fluid to leak back.

    Thanks.
    It's caused by the ABS, and is perfectly normal for a C5 [as David S says]. Replace the brake M/C if you will but it won't cure anything.

  7. #7
    Fellow Frogger! dieselman's Avatar
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    Default Re: Try this on your C5 and let me know the results

    I think I'll leave it well alone.
    The brakes are quite good now after the dealer bled them.
    Leon

    1987 Peugeot 505 GTD
    2010 Citroen C5 3.0 V6 HDi
    2010 Citroen C5 3.0 V6 HDi (wife's car)

  8. #8
    Banned Haakon's Avatar
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    Holy crap - who is this dealer and why are they not on ACA for dangerous advice!!??

    The C5 (as far as I know, please correct me otherwise) has conventional brakes. This is a standard classic sigh of a failing master cylinder and it should be replaced immediately. As in now, without delay!

    Flipping 'eck... Do they not want the job or something?

    My ABS owning experience is a 406, a Xsara2 (C5 running gear in a 306 chassis), a Laguna and a Megane (and a Magna with German Bosch ABS) - none have done this.

    ABS is an "in line" system - it does not and cannot allow pressure to bleed off.
    Last edited by Haakon; 22nd March 2013 at 09:56 PM.

  9. #9
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    Quote Originally Posted by Haakon View Post
    Holy crap - who is this dealer and why are they not on ACA for dangerous advice!!??

    The C5 (as far as I know, please correct me otherwise) has conventional brakes. This is a standard classic sigh of a failing master cylinder and it should be replaced immediately. As in now, without delay!

    Flipping 'eck... Do they not want the job or something?

    My ABS owning experience is a 406, a Xsara2 (C5 running gear in a 306 chassis), a Laguna and a Megane (and a Magna with German Bosch ABS) - none have done this.

    ABS is an "in line" system - it does not and cannot allow pressure to bleed off.
    That's incorrect, but anyway it's just lost its residual is all, perfectly normal and it will probably improve over time once the valves find their seating. A new brake M/C will fix nothing.

  10. #10
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    Quote Originally Posted by shanadoo View Post
    That's incorrect, but anyway it's just lost its residual is all, perfectly normal and it will probably improve over time once the valves find their seating. A new brake M/C will fix nothing.
    +1
    I agree 100%

    Apart from which, if you had your foot on the brake, pressed hard to the floor for 15-20 seconds without releasing and hadn't stopped, what speed were you doing when the brakes were first applied and why did it take so long to stop. Even if you were on an oil slick, in an ABS equipped car, the brakes would've released and applied any number of times.

  11. #11
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    My V6 Triton does this from new. After 5 1/2 years of hard use it never fails to pull me up.
    CitroŽn's that own me

    - 2008 C5 X7 Tourer (Estate) 2.7 DoubleTurbo Diesel UHZJ - V6.

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    - 1990 BX TRI Estate Auto. (Traded In)
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  12. #12
    Banned Haakon's Avatar
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    Where does the pressure go? Never ever seen it on the hundred or so ABS cars I've driven - whats so unique about the C5?

  13. #13
    Fellow Frogger! dieselman's Avatar
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    That's what I'd like to know too.
    Not many C5 owners wanting to try it on their own cars either.
    Strange that it only loses pressure when there is boost (motor running).
    Leon

    1987 Peugeot 505 GTD
    2010 Citroen C5 3.0 V6 HDi
    2010 Citroen C5 3.0 V6 HDi (wife's car)

  14. #14
    Fellow Frogger! flipperman's Avatar
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    Maybe it's just pushing down more due to a constant force being applied, then when you let go of the pedal it returns back to normal?
    CitroŽn's that own me

    - 2008 C5 X7 Tourer (Estate) 2.7 DoubleTurbo Diesel UHZJ - V6.

    CitroŽn's that formally owned me

    - 1990 BX TRI Estate Manual. .. . "Phoenix" - "Donated to Science"
    - 1990 BX TRI Estate Auto. (Traded In)
    - 1987 BX TRI Hatch.

    -------------------------------------------------------------
    Australian Citroen BX - All about the Citroen BX in Oz
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  15. #15
    1000+ Posts gerry freed's Avatar
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    Mine developed a longer pedal travel and with the engine running and the car stationary you could slowly depress the pedal almost to the floor. The mechanic suggested a change of master cylinder which seemed logical and so I bought one for him to fit. There were two versions and the one with the stability control like mine was nearly three times the price (both versions coped with ABS). I wasn't able to drive it much after he changed the master cylinder as he stuffed up the suspension but the brakes were just the same. I could slowly push the pedal down against resistance to the floor.
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  16. #16
    1000+ Posts bigkev414's Avatar
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    I had one and while I didn't actually do what you said I noticed that waiting at the lights for instance the pedal would slowly sink almost to the floor. Always felt 'spongy' compared to other cars I've had. Bought a Peugeot 3008 and it felt similar. Stopped ok, but did feel 'soft' and gave me that 'sinking feeling'.
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  17. #17
    Banned Haakon's Avatar
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    I still don't buy it... Until someone can tell me why this is so, all I can think is pressure loss/bypass.

  18. #18
    Fellow Frogger! flipperman's Avatar
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    A HSV mechanic friend of mine informed me of this info. This anomaly happens only in a duel brake master cylinder which incorporates two pistons jointed together by a spring and a retainer pin. While sealed at each end the spring and retainer pin area has air in it, when you push on the pedal you push on the spring and the spring pushes the 2nd piston but by doing so it compress the air a little, by continuing pressing harder and harder the air is compressing more, moving the first piston further along thus allowing pedal movement, by releasing this pressure the spring and the compressed air return to normal. This occurs in new and rebuilt duel brake master cylinders. You are able to improve this issue by performing what is known as bench bleeding the cylinder. Otherwise it's normal action.

    Please: don't confuse this action with a pedal that fails to return quickly to hard again. Get your brakes checked if your pedal does not return quickly or your brakes lack solid pressure.
    Last edited by flipperman; 24th March 2013 at 08:27 PM.
    CitroŽn's that own me

    - 2008 C5 X7 Tourer (Estate) 2.7 DoubleTurbo Diesel UHZJ - V6.

    CitroŽn's that formally owned me

    - 1990 BX TRI Estate Manual. .. . "Phoenix" - "Donated to Science"
    - 1990 BX TRI Estate Auto. (Traded In)
    - 1987 BX TRI Hatch.

    -------------------------------------------------------------
    Australian Citroen BX - All about the Citroen BX in Oz
    -------------------------------------------------------------

  19. #19
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    Have just purchased a D9 406 SV, which also exhibits this behaviour. If it wasn't for this thread I would have assumed that there was a problem, as the sinking of the pedal is quite noticeable. Does anyone know if an 09/2000 build 406 has a dual master cylinder?

    Flipperman, your explanation makes sense - air somewhere in the system would certainly allow pedal movement. From the name, I assume that a "bench bleed" is done with the M/C out of the car (thus allowing more air to enter the system )?

    Cheers

    Alec

  20. #20
    bas
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    I tried it on my C5 yesterday and my pedal slowly sinks but never goes all the way to the floor. Does that help?
    Life is what happens to you while you're busy making other plans.

  21. #21
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    Quote Originally Posted by bas View Post
    I tried it on my C5 yesterday and my pedal slowly sinks but never goes all the way to the floor. Does that help?
    C5 has single cylinder M/C. Pedal creep is normal, normal, normal. On all systems the ABS only works with motor running [the ABS ECU requires 13.7v min to operate from memory, but I could be wrong it may be higher] against a general system voltage of 12.2 max with motor off. Some pedals don't go right to floor as M/c usually runs out of stroke/travel.

    HSV guy has got hold of some pretty good smoko evidently. Half his luck.

  22. #22
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    Quote Originally Posted by shanadoo View Post
    C5 has single cylinder M/C. Pedal creep is normal, normal, normal. On all systems the ABS only works with motor running [the ABS ECU requires 13.7v min to operate from memory, but I could be wrong it may be higher] against a general system voltage of 12.2 max with motor off. Some pedals don't go right to floor as M/c usually runs out of stroke/travel.

    HSV guy has got hold of some pretty good smoko evidently. Half his luck.
    Sorry about the "HSV guy" crack, it is not intended to be derogatory. Just a weak attempt at workshop humor.

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