brake judder air?

[John Plum]

The hardest work is out of the way. I've replaced all the spheres, and the LHM with with hydro-flush. Then bled the brakes. Fluid with many interspersed tiny bubbles came out of both rear brakes. I drew about 500m -600 ml ml from each side, until it was running clear.
The sound is still there, though it may have improved, not sure.

I got hold of the black tube behind the brake pedal, but could only pull it out a few mm. It didn't seem to twist out. I didn't want to break anything, although I used a fair amount of force. SO I stopped. It seemed as if I could feel a spring in there.

I haven't changed the brake hoses yet, as they haven't arrived yet.
When I change the hoses, I can just de-pressurise the system and remove them or not?

[citronut]

John wrote
"When I change the hoses, I can just de-pressurise the system and remove them or not? "

you dont have to de-pressurise the system at all when openning the brake circuit, as there is no presure in there till you press the brake pedel,

also did you clean the hydraulic tank filters whilst you were changing the LHM for hydraflush

regards malcolm

[John Plum]

Hi ya Malcom! Yes, I cleaned the two filters , and wiped out the tank.

Today I fitted two new front brake hoses, and bled the front. A lot of air, like gulps and some large bubbles came out, not so many small bubbles, but some..., running clear on n/s after 400-500 ml, and on the d/s after 200-300 ml approx.
Only a short 1/2 mile hop to get fuel. The sound and pulse is still there but seem to be improved - not so frequent or so loud, perhaps. About 10+ citrobics, since fitting the spheres, and with fitting the brake hoses in between.
I know I must do a complete bleed again front and rear; I want to use a tube into the reservoir, and must get some. That may do something.

I wonder if a duff ABS ecu could produce this symptom?

[CitroJim]

John, slightly OT. Have you received your repaired blower module yet? Went in the post on Monday, first class...

[John Plum]

Yes, thank you Jim! I've just fitted it now, and it works a treat. Delighted! I received it yesterday.

[John Plum]

duplicate post!

[John Plum]

I suspect a very slow seepage from the mounting bolt/pipe feed at the back (n/s) of the regulator. I seem to have to rev a bit to get the car to adjust height. The seepage is very slight. What could this be doing to the brakes do you think? It'll probably be sorted by a THOROUGH bleed, but best forewarned.

[John Plum]

I seem to have to rev a bit to get the car to adjust height.

That so when lowering.

[CitroJim]

Should not have to rev it to adjust height John. Sticky height corrector most likely. If mechanically free, see what a good Hydraflush and LHM change brings about. Have you checked the filters in the LHM reservoir? They are likely to need a good clean. Don't be surprised if they appear to be wearing fur coats when you look at them!

Pleased the blower module is good. I was worried given the state of the postal service at this time...

[John Plum]

Sticky height corrector most likely. If mechanically free, see what a good Hydraflush and LHM change brings about.

I'll watch for some improvement there then; it's mechanically free
I did clean out the filters. They weren't bad.
I was pleasantly surprised at the speed of the post.

[John Plum]

The problem remains, when braking (but not handbraking).
I just bled all brakes again using a tube from nipple to reservoir. No air this time, or small nitrogen bubbles.

The back brakes free up when off, and stop the disc when pressed (pistons at moving).

Haven't a clue what to think next. I dream of rescue!

[John Plum]

Other than this problem, the car is ready for its MOT. I don't suppose I can present it like this can I?

[John Plum]

Possible causes I'm thinking of:

• A. locking brakes, at the back maybe, causing the ABS to come on - may be with o remaining air problem.
  B. Air in the system somewhere in the brake circuits - the Regulator?

[VertVega]

The sound and pulse is still there but seem to be improved - not so frequent or so loud, perhaps.

This was a long thread (sorry, I didn't read all) but I would like to ask about this sound and pulse.
- Do you hear it only when you press the brake pedal?
- Is the pulse from the brake pedal, like ABS kicking?

[John Plum]

Hi VertVega: Thanks for reading and considering this thread:

Yes, the pulse and sound only occur when pressing the pedal.
It is something like the ABS kicking in I guess, rapid click-pop with a reverberation like in a box, like ..the sound seems to come from somewhere near the pedal (e.g. doseur valve), under the bonnet.