Do C5 brakes require special bleeding techniques?

Johnno · Post by **Johnno** » 22 Apr 2011, 17:56

I've had to change one of the front calipers on my 2.2 and I cannot now appear to get the system working properly. I've bled through more fluid than I wished to pay for but still have the situation where the pedal goes to the floor (though only with the engine on). I've read of a similar situation where the owner had to take the vehicle to the local stealer, where strange incantations and weird rituals fixed it.

I wonder if I've damaged the master cylinder seals, but before going to all the expense and effort of changing it, has anyone had similar experience and is there a fix?

Between that, the leak in the screen wash bottle, the non-removable alternator pulley and the uncontrollable dog next door, it's been a long Good Friday...

Post by **myglaren** » 22 Apr 2011, 18:00

Mine were a bit like that immediately after the caliper change and I was all set to take it back but it firmed up by the following morning after being driven about ten miles. I noted that the fluid was a bit down from the max level where I like to see it.

Johnno · Post by **Johnno** » 22 Apr 2011, 18:30

I might give the old road test a try - though my heart quakes a bit at the potential for disaster! Perhaps first thing Sunday morning.

I wonder just how common the "damaged cylinder seals" thing really is. I've worked on brakes on many different vehicles, most with a pretty high mileage (the C5 is at 190k and climbing) and I don't think I've ever experienced it.

cachaciero · Post by **cachaciero** » 22 Apr 2011, 19:41

Yes! if the system has been well depleted you will need a Lexia to set some valves in the ABS unit to allow bleeding.

cachaciero

addo · Post by **addo** » 22 Apr 2011, 22:39

You can't just crack the flare nuts on the ABS block and let gravity do its' thing? That would fill the pipe from master to ABS block.

I thought ABS units - when powered down - defaulted to full flow at all wheels. Do they have a pressure drop shuttle arrangement in them to act a bit like the old split system safety valves?

KevMayer · Post by **KevMayer** » 23 Apr 2011, 07:04

I had this on an Audi A4 after I'd replaced some corroded brake pipes from the ABS block out to the callipers.

The problem was air in the ABS unit and, after searching forums, the sollution was to go for a run and apply the brakes hard enough for the ABS to cut in. Then bleed the brakes again. This worked.

KevMayer · Post by **KevMayer** » 30 Apr 2011, 15:24

Johnno,

How are your C5 brakes ?

Any update on this one ?

Johnno · Post by **Johnno** » 01 May 2011, 19:33

Hi Kev. Been down in Cornwall for the week, forgetting all about perfidious vehicles (didn't go in the C5, I hasten to add). Brakes are still the same. I took the car out last weekend and managed to get the ABS working on several occasions, followed by further bleeding, to no avail.

The car stops alright, but the brakes just don't feel correct. I'm hoping a mate has been able to get some info from his local Citroen dealer during the week. It may well be the master cylinder, I suppose, but I'm not giving up just yet.

I'll update with progress.

Cheers.

Johnno · Post by **Johnno** » 07 May 2011, 12:02

"They're all like that, sir" - and, you know what? I think he may be right. Aforementioned friend visited the local Citoroen dealer and spoke with a very helpful chap who described what the brakes are like and what the issues may be. It's certainly true that they've improved and I find that if I press and hold, the pedal only goes so far. It seems that there is a very high servo action, resulting in a lot of compliance in the flexible pipes. This can give the impression that there is air in the system.

Worth a footnote and backs up what others have said about 'bedding in' after a few miles.

Thanks for the help.