Synergie - Sinking brake pedal

[Gammy leg]

not knowing what car

The clue is in the title

[Gammy leg]

..or the servo leaking - I assume they still use them.

Yes a servo is present but what effect would a leaky one have?. Surely the opposite symptoms to what I am experiencing.

Gammy

[Gammy leg]

not knowing what car i'm guessing at this but does it have a rear brake compensator i know this hasn't been disturbed but there is a slim chance it has air in it
it does sound like a rear wheel cylinder from the symptoms described but as its discs all round are the rear caliper seals weeping is fluid in the reservoir dropping
just ideas that have probabley been mentioned but ya never know

I'm sure there is a rear compensator, but I have flushed through the complete system front-to-back so any trapped air should have been dislodged.
The rear brakes are drums rather than discs but no evidence of leakage here either.

Sorry for the multiple posts, but I have not mastered the art of inserting more than one quote into a single post.

I may have found a replacement master cylinder on eBay, would anyone be able to confirm what the equivalent Bosch/Citroen part no. is for the attached item?

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... K:MEWAX:IT

Thanks

Gammy

[citronut]

if you give me your chassis No. i will get you the corect OE part No. for your car from pug service box,

i also still belive the master cylinder pistons travel further up there bore's whilst the system is open (bleed kniple open), than in normal use,

because with the system under presure there is no way they can move the full lengthof there bore's

regards malcolm

[MJM]

If the pedal is sinking to the floor and there are neither fluid leaks nor faulty flexible hoses then the fluid in the master cylinder has to be going somewhere else. It would be worth looking at the level in the fluid reservoir while someone depresses the brake pedal. If the level rises as the pedal is being depressed then fluid is being forced back into the reservoir. This suggests that the seal which closes the reservoir off to the rest of the system is not working properly. The initial movement of the pedal causes a seal (or seals on a twin circuit system) to isolate the reservoir from the rest of the system. Further movement of the pedal can then apply pressure to the system.

The OP has bled the system so it should be free of air. The only work done was to change the pads.

[tonupteabag]

not knowing what car i'm guessing at this but does it have a rear brake compensator i know this hasn't been disturbed but there is a slim chance it has air in it
it does sound like a rear wheel cylinder from the symptoms described but as its discs all round are the rear caliper seals weeping is fluid in the reservoir dropping
just ideas that have probabley been mentioned but ya never know

I'm sure there is a rear compensator, but I have flushed through the complete system front-to-back so any trapped air should have been dislodged.
The rear brakes are drums rather than discs but no evidence of leakage here either.
in some circumstances the rear slave cylinders are leaking but if they have only just started then there is no evidence on the outside of the drum as it can take a while to get past the outer dust covers so isn't evident straight away but as was posted earlier keep an eye on the fluid before condemning the master cylinder just my take on it

Sorry for the multiple posts, but I have not mastered the art of inserting more than one quote into a single post.

I may have found a replacement master cylinder on eBay, would anyone be able to confirm what the equivalent Bosch/Citroen part no. is for the attached item?

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... K:MEWAX:IT

Thanks

Gammy

its worth having the rear drums off just to make double sure that the wheel cylinders are ok as they would be cheaper than the master cylinder IMHO

[tonupteabag]

not knowing what car

The clue is in the title

[Gammy leg]

if you give me your chassis No. i will get you the corect OE part No. for your car from pug service box,



i also still belive the master cylinder pistons travel further up there bore's whilst the system is open (bleed kniple open), than in normal use,

because with the system under presure there is no way they can move the full lengthof there bore's

regards malcolm

Thanks Malcolm, Chassis No is VF7**************[VIN obfuscated, can be read by forum staff]. What I would like to know is if the cylinder off eBay is compatable with the OE Bosch unit that is fitted at the moment. I have googled the Delphi part no and it returns that it is a replacement for a Bendix system but it looks to be identical to the Bosch ( albeit a little more angular in appearance ). I don't know what other systems were fitted to Synergies or whether they could be substituted with other manufacturers parts. The servo is also a Bosch but the calipers are Lucas

Agree that forward travel of the piston whilst bleeding would send it into unchartered territory which may have caused the seals to become contaminated / damaged.

Thanks

Gammy

[Gammy leg]

in some circumstances the rear slave cylinders are leaking but if they have only just started then there is no evidence on the outside of the drum as it can take a while to get past the outer dust covers

Thanks for the input, however the amount of pedal pushes given to this thing yesterday afternoon would mean that the street would be awash with brake fluid if the rear slave seals were leaking. I reckon that it would take between 15 - 20 full depressions to flush the whole system out including what is in the reservoir and I have probably done this number 5 times over so far with no signs of leaks.

I am beginning to think along the lines of MJM ( and others ) that something has gone amiss inside the master cylinder. I will have a look at the fluid level in the reservoir while someone presses the brake pedal to see if there is any evidence of backwash.

Thanks all for your help so far. I will defo post once this is resolved.

Gammy

[citronut]

here is trade price and part No. that comes up with your chassis No.

Part Number Description Quantity Price excl. VAT Price incl. VAT Total incl. VAT Selection
4601K2 MASTER CYLINDER 159.86 GBP 187.84 GBP 187.84 GBP


i forgot were i were earlyer when i mentioned pug service box silly me

regards malcolm

[Gammy leg]

Thanks Malcolm, any idea whether it is compatible/same as this one?

DELPHI (BORG & BECK ) LM 21012. My research suggests that this is a replacement for Citroen/Peugeot ref. 4601 E2. There is £160 difference in cost so I know which one I'd prefer to get, if it were suitable.

http://www.yiparts.com/Part/en/NNNVRC

http://www.yiparts.com/Part/en/SWGDRA

Gammy

[Brigsygtt]

The master cylinder is at fault imo.

A couple of weeks back i had exactly the same problem with my r5gtt, new pads etc & bled the brakes, pedal went to floor & never recovered, would pump up but no where near satisfactory. I dont know what happened but it was shot on one circuit.

Always clamp flexi/open bleed nipple when bleeding brakes, seen a fair few mastercylinders fail when not done.

[Gammy leg]

Always clamp flexi/open bleed nipple when bleeding brakes, seen a fair few mastercylinders fail when not done.

To late for me, but wise words mate.

Gammy

[HDI Dave]

..or the servo leaking - I assume they still use them.

Yes a servo is present but what effect would a leaky one have?. Surely the opposite symptoms to what I am experiencing.

Gammy

I had this on my transit van. Pedal sunk to the floor, it was the servo. Tenner from the scrappers and all was well again.
But,symptoms also included - more effort on the brake pedal,(obviously,as they were in effect unassisted), and a pssshhh sound, like air brakes,on pressing the pedal.
If you don't have these symptoms then maybe you could rule out the servo.
Strange how it only appeared after changing the pads...caliper area?
Otherwise the master cyl as already mentioned is what i'd be thinking.

Who knows, just my two penath!

[Peter.N.]

I have known failed seals in the master cylinder to leak fluid into the vacuum chamber. I was initially thinking about a seperate servo with its own cyclider but I dont think they have used those sine the ''60s I've been running hydropnumatic Citroens too long

Peter