Help C5 brake pads gone wrong - deep diver
Hello
I have just changed my front brake pads on my 2003 citroen C5. Everything seemed to go OK wound the caliper pistons back in Near side clockwise Offside anti clock wise no problems I gad some brake fluid come up out of the resevoir as I wound the pistons in but thought no problem that is normal. Pumped the pedal a couple of times which brought it up to the top so I thought good job done. then I started the engine up and the problem started. With the engine running after 10 seconds the pedal goes to the floor It pumps up hard take your foot off the pedal and 10 seconds later it goes to the floor. This only happens with the engine running. turn thr engine off and the pedal stops hard.
The hand brake is OK with or without the engine running. This indicated air in the system to me but I have not touched the hydraulic side. On this I have bleed both front brakes just in case but no change. Any body got any ideas please

Thanks in Advance

Mark
Help C5 brake pads gone wrong - George Porge
Sounds like you've inverted the master cylinder seals. You say you pumped the pedal...as in hard? You need to be very gentle to avoid damaging the master cylinder seals. Lots of people now recommend openning up the bleed nipple on the calliper before pushing the pistons back. I've never had a problem after a pad change but I'm very gentle pushing the piston back, insert new pads, gently press on the pedal until firm, then repeat the other side
Help C5 brake pads gone wrong - deep diver
Hi
Thanks for the reply Yes I pumped the pedal but not hard just as you would normal braking until the pedal became hard. If I had inverted the master cylinder seals wouldn't this happen with the engine not running as well as running. It has been stood now for over half an hour and the pedal is still hard. start the engine and down it goes.
Help C5 brake pads gone wrong - Altea Ego
Basically your brake system does not work when the engine is not running. The engine driven servo assistance is the only way to produce the required pressure in the system to brake properly. Hence any problems in the system wont show up unless the engine is running.

You have a basic brake system problem, engine running or not has nothing to do with it.
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TourVanMan TM < Ex RF >
Help C5 brake pads gone wrong - George Porge
Long pumps of the pedal after a pad change moves the piston in the master cylinder beyond its normal travel and the seals invert. I doubt anyone could 100% dignose the fault correctly without seeing the car
Help C5 brake pads gone wrong - Civic8
tend to agree with you there Dox!
--
Steve
Help C5 brake pads gone wrong - Mike-H
The brake system works fine when the engine is not running, it just needs more pedal pressure, for the same result, and in an emergency you'll find it! It's a failsafe requirement of construction and use regs I think. Mike
Help C5 brake pads gone wrong - Altea Ego
The brake system works fine

you ever tried it? Belive me you need legs like a JCB to produce anywhere near the same stopping power.
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TourVanMan TM < Ex RF >
Help C5 brake pads gone wrong - Mike-H
Hi TVM, I have been towed a couple of times with no engine, and no power steeering, and couldn't agree more with the legs like a JCB ! Frightning ! All a servo does though is decrease the pedal pressure needed for a specific braking effort, it does not make the brakes any better. I say this only to let non- technical people know. I totally agree with your findings though, it's a braking fault and nothing to do with the engine, unless it is an ABS system and the pump is damaged, though they are most usually electric. Don't know on the C5. Mike
Help C5 brake pads gone wrong - Mike-H
I think you may have pumped debris back into the master cylinder, which is stuck behind the seals preventing them from returning to their correct position. When you lift the pedal, the seals lift off their seats allowing fluid from behind to return to the chamber in front of the seals. They then should normally return to the seat and seal ready for the next application. You could try rapid bleeding to try and dislodge the debris, or better pressure bleeding which should do the same thing by pumping fluid from behind the seals. Hope this helps. Mike
Help C5 brake pads gone wrong - Mike-H
Is it an ABS system?
Help C5 brake pads gone wrong - deep diver
Hi
Yes it is an ABS system
Help C5 brake pads gone wrong - Mike-H
In that case, deep diver, I should change your name to deep doo doo instead. I'll have a think, but not too much experience with Citroen. Mike
Help C5 brake pads gone wrong - deep diver
This doo doo is deeper than you think I'm supposed to be setting of to France on Frisay for the family holiday !!!
Help C5 brake pads gone wrong - Mike-H
On reflection, I think you will need to get it to a Citroen specialist who knows the bleeding procedure, and bleed the system thoroughly. You could make it worse. Whilst I'm not familiar with your system, I do know that if you manage to get air in the modulator, some are impossible to bleed, and their replacements come charged with fluid form the factory. Also, I suspect muck has got in the ABS somewhere and will need bleeding out. You might try pressure bleeding it, but again on some systems you need to 'run down ' the system with 40 or 50 pedal pumps first. If you do not have a pressure bleeder, I have used a push bike pump on occasions, with a valve stolen from my son's bike screwed into the master cylinder lid in the slightly enlarged air vent hole. If you do manage to get a pedal, I would still tend to get it checked over by an expert before you set off. I'm going on Wednesday to Brittany, could offer a lift in the back of my van if it helps. Mike
Help C5 brake pads gone wrong - Mike-H
maybe not www.honestjohn.co.uk/forum/post?v=i&t=600
Help C5 brake pads gone wrong - George Porge
How would air get into the brake system by changing pads?
Help C5 brake pads gone wrong - Dynamic Dave
How would air get into the brake system by changing pads?


I don't know how, but I do know it's possible as it's previously happened to me when I've changed the pads on an Astra.
Help C5 brake pads gone wrong - Mike-H
I don't think its air that needs bleeding out, I think its muck in the ABS valves or master cylinder that wants bleeding through. The easiest way to get air in whilst bleeding is to inadvertantly let the master cylinder run dry. Plenty do! You can also suck air in back up the bleed nipple if you are unlucky and uncareful.
Help C5 brake pads gone wrong - mfarrow
maybe not www.honestjohn.co.uk/forum/post?v=i&t=600


Just read through this thread, and I thought I'd point out don't read into the 'silicon fluid' (DOT 5) bit nearer the bottom, not good for ABS systems. DOT 4 or DOT 5.1 is OK.

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Mike Farrow
Help C5 brake pads gone wrong - bignick
The Citroen C5 with ABS cannot be bled conventionally - I am pretty sure this has to be done while the vehicle is connected to a Citroen dealers diagnostic system. Best get hold of your dealer for advice.
Help C5 brake pads gone wrong - Xileno {P}
Bignick is probably right, certainly Renaults with ABS/EBD need to be connected to CLIP in order to be bled.
Help C5 brake pads gone wrong - LeePower
The C5 uses a normal servo & ABS / EBD / EBA modulator set up & should be bled with pressure bleeding equipment.

Pretty sure that the OP has by not letting the excess fluid out via the calliper bleed nipples when pushing the pistons back has either got dirt in the ABS unit ( if his lucky ) or has ruined the seals in the master cylinder, Either way it needs looking at before the car is driven on the road again
Help C5 brake pads gone wrong - deep diver
Thanks to all who replied to my problem. I took the car to an independent Citroen garage who bled the brake system and told me everything was OK they had road tested the car and it braked as expected with the ABS working correctly but the pedal did still feel spongy.
During a chance conversation with another non Citroen mechanic he assured me the pedal would feel OK after the new pads had been bedded in. He assured me everything would have been be OK if I had changed the discs at the same time as the pads and I would not have had a problem. I was very skeptic but as the brakes seemed to work all right when actually braking and the impending trip to France I had no choice but to believe him. I had checked the braking performance myself and the car did indeed brake very well with the ABS working fine however if I sat with my foot on the brake at a stand still my foot still slowly sank to the floor. I am happy to report he was correct in his advice. After a week of running around the brakes are perfect. I still do not understand what was wrong but everything is now OK. Again thanks to every body that tried to help
Help C5 brake pads gone wrong - Mondaywoe
I had a similar experience with my C5. I changed the pads all round and although the brakes held well enough, there was a sponginess to the pedal that wasn't there before. Fortunately the car was going into the dealer the following week for its service so i mentioned it to them. Car came back with brakes nice and firm again - they said they'd bled them and all was well.

I did, however, open the bleed screws wheh retracting the pads (to avoid sending dirt back up into the ABS valves) and I was wondering if I'd allowed a bit of air back into the system. Maybe it is just a case of letting things bed in. I didn't change the discs either.

You do have to be careful with C5 brakes. The front caliper pistons have to be 'screwed' back in to the caliper - N/S clockwise and O/S anticlockwise. Getting it wrong can disrupt the handbrake mechanism (built into the front calipers on Cits) - or even destroy a caliper.

Graeme
 

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