Bleeding C5 brakes

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martinwiseman2000
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Bleeding C5 brakes

Post by martinwiseman2000 »

This is probably elementary stuff, but after nearly a quarter of a century driving fully hydraulic Citroens the conventional brakes on my C5 are nearly as alien to me as hydractive suspension would be to the average Mondeo driver.

My C5 (57 reg 2.0 HDi) had brakes that seemed fine under light braking but the pedal could be pushed all the way to the floor under heavy braking without the ABS kicking in. Pumping the brake pedal results in better braking and the pedal then can't be pushed all the way down. From what I remember about conventional brakes this is (could be?) a symptom of worn master cylinder seals.

I tried bleeding the brakes and initially thought I had made a big improvement but as soon as I started the engine it felt soft again (although is it noticeable better than it was).

Now I am wondering if:
a) I didn't bleed the brakes enough (At each corner I pumped the brakes about 20 times - enough to take the reservoir from max to min. Total fluid volume no more than half a litre from all 4 corners).
b) The master cylinder does needs to be replaced.
c) It is related to an ominous note in Haynes "Failure to bleed satisfactorily after a reasonable repetition of the bleeding procedure may be due to...air trapped in the ABS modulator, in which case...the system bled using Citroen dedicated diagnostic equipment"

My questions are:
Is the brakes improving when the pedal is pumped definitely an indication of a master cylinder problem?

How much fluid should I expect to pump through the system when bleeding?

Any other suggestions?

Thanks,
Martin.
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Post by addo »

Sounds like you still have trapped air in the system.

With a complete flush, I expect to bleed a good pint through. Lexia or similar will allow full brake fluid flow when a wheel is not rotating.
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Post by myglaren »

I found similar symptoms on mine, first after the rear discs and pads were renewed and later, earlier this year when the pads, handbrake cables and a calliper were renewed on the front.
The brakes worked but there was a lot of travel on the pedal, over a couple of weeks this righted itself and the brakes are fine now.

Oddly enough I didn't have that on the replacement of the front discs and pads, shortly after buying the car.

My ABS very rarely comes in to operation, only happened a couple of times in icy conditions.

On a quiet road, do an emergency stop from around 90mph. The Brake assist should come in, which can be fairly dramatic as it flashes all the lights at the same time but is quite impressive the way it pulls the car up rapidly but without locking the wheels.
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Post by cachaciero »

According to the Citroen Docs on this a Lexia is required to open a couple of valves in the ABS block required to enable complete bleeding.
Some have said that if the system has not been drained down completely this is not neccessary am not convinced personaly but have no practical experience so cannot comment further.

cachaciero
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