Foot brake problem - steering and apply the foot brake, pedal goes to the floor

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Hi, I have a c3 on a 12 plate which has started having a pretty serious brake problem. Every now a then when I apply the foot brake the pedal goes down to the floor without resistance, and the brakes do not take affect. If I then lift my foot and apply the brakes again they work as they should. This has only ever happened at very slow speeds of less than 10 mph, usually while parking or other slow manoeuvres. But obviously it's become a concern in case it happens at speed.
I have had the brake fluid changed along with pads and discs, and a recent mot but the problem is still there. Any advice would be greatly received.
Thanks Martin
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Hi Martin.

This is a very serious problem and could have some very serious consequences if it happens at speed.

The car should not be driven in this state.

If its going to a garage, it will need to be towed.

If you wanted to investigate further, look at the brake servo and master cylinder, but also the abs and esp if yours has it. But I would suggest having it taken to a Citroen dealer for this.
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Hello also have had this problem. Do we know what the final out come was and what was the problem with the car?
Thanks Wes
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Dannyds3 wrote: Wed Nov 06, 2019 11:01 pm Hello also have had this problem. Do we know what the final out come was and what was the problem with the car?
Thanks Wes
Almost certainly a failed brake master cylinder fault. Failed servo would result in very hard brakes, problem with abs would probably not be noticed in normal driving apart from warning light being on.
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Dannyds3 wrote: Wed Nov 06, 2019 11:01 pm Hello also have had this problem. Do we know what the final out come was and what was the problem with the car?
Thanks Wes
Could be a failed brake master cylinder fault, although as the system is probably dual circuit both circuits need to have failed. Another possibility is a leak somewhere resulting in no fluid remaining in the reservoir. Check the level. Failed servo would result in very hard brakes, problem with abs would probably not be noticed in normal driving apart from warning light being on.
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I’ve got a 62 plate c3 1.4 diesel, I’ve got the same issue, it started 9 month ago, when parking or manoeuvring slowly, if I got on full lock in any direction I get a clunk from the nsf and the brake Pedal hits the floor, take my foot off and press again and the brake is back to normal, it’s almost as like the calliper is being pushed back on lock, took a look at the discs and pads and they were about 3/4 worn so I replaced them, problem was solved till last week when it started doing it again, not had another look since but can anyone shed any light? Would be appreciated
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As mentioned above this "appears" like a master cylinder failure BUT I have never seen a master cylinder fail intermittently then MAGICALLY start working again. Particularly under identical circumstances as somebody else's car! If the seals go, then they go. There are two diagonal breaking circuits. A failure in one master cylinder seal does not affect the other circuit. Braking will be reduced but will still work. The chances of BOTH circuit seals going is astronomical. HOWEVER loss of fluid pressurefrom the system E.G. a cut brake line or loose bleeder valve WILL cause the peddle to go to the floor and loss of braking. Again, this doesn't magically fix itself!! AND you will loose brake fluid out of the system.

Another thing, the ABS module monitors circuit pressures and if there is a "problem" it will bring on the ABS light. If the ABS light doesn't come on...it doesn't "think" there is a problem. Particularly if it's the thing bleeding off the pressure!

This sounds like an ABS "bug". I would get in touch with Citroen and see if there is a service bulletin about it.
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C3bri wrote: Tue Feb 11, 2020 5:34 pm I get a clunk from the nsf and the brake Pedal hits the floor, take my foot off and press again and the brake is back to normal,
Ozvtr wrote: Tue Feb 11, 2020 6:55 pm This sounds like an ABS "bug". I would get in touch with Citroen and see if there is a service bulletin about it.
The only thing I can think of that could possibly cause this odd brake pedal behaviour where it recovers immediately is the ABS block. As Ozvtr says, Citroen should really be consulted about this because they need to know its happening. It is more helpful if you can demonstrate the failure on demand.

The clunk is more likely to be valves in the ABS block than the calliper because it recovers (electrical fault as opposed to a mechanical fault).
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have this problem too, only at parking speeds and on full lock ,I think it's in the ABS system definitely not fluid related or pad knock back,
if anyone finds out what this is please let me know
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Had mine in the garage and found the antiroll bar bushes had worn and the antiroll bar had moved towards the drivers side 4 inches , so when on lock the antiroll bar was pressing on the back of the osf calliper, pushing the piston back, had no knocking from the bushes, undid the antiroll bar bush clamps and moved the bar over so it was central, all sorted 👍 no more pedal loss on lock
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