brake judder air?

[vince]

Vince wrote
"He got the calipers checked and hey presto....i was right "

whats it (no not PERCY) like beeing right all the time Vince,

i keep tryingit but i never get it quite right TEA HE,

regards malcolm

Far from it Malc, im often wrong...The main part of our job is answering queries over the phone without seeing the vehicle....a bit like here i guess, so there is always scope for getting stuff wrong...especially on later model vehicles

[Old-Guy]

When researching discs for my own '95TD estate, from a variety of sources I compiled and cross-checked the following data:

FRONT (Ventilated)
Dia Thick
266 x 20.4 was fitted to most hatchbacks.
283 x 22 should be fitted to estates and higher power hatchbacks.
288 x 28 S1 - only V6. S2 - all HDi 110 & V6, plus 2.0 CT & 2.1 TD after RP 8001.

REAR (Solid)
224 x 9 Hatchbacks
251 x 12 Estates

There are tales of 1.8 petrol hatchbacks built with 283 discs and estates with 266s. As callipers are different for each size of disc, check before reaching the point of no return!!

The data above, plus a step-by-step guide to changing pads and discs can be downloaded as a PDF file

[John Plum]

@ OLdGuy Hey hey, I just returned from a trip to the spares shop with a set of discs and pads.

[John Plum]

I got back from the spares and GSF Brixton had given me the wrong pads, i discovered with the brakes stripped in the street, and the shop an hour's bus ride away in the traffic. That was after I asked them to check it was right, it was the same as for smaller discs surely not? They didn't look right, according to memory. They checked and assured me.
When I rang GSF later, they checked again and said the right ones were not in stock until Monday; 'That bit of their catalogue was a bit ropey '
Luckily the local spares shop had the right ones. I fitted them, a race against daylight. But now I'm having a cup oof tea, having changed out of my filthy overalls, before I test drive.

The good news so far: Near side disc was hotter on a just a three mile traffic run than the n/s.
I'll let you know the outcome soon, this evening. I'll take bets: £1000.00 it's solved (kidding).

[John Plum]

It's much better. Not pulling to one side now.

But... the pulsing and noise like tin farts..through the pedal is still there. Not sure if there once on the test run, there was faded braking at the start of the pedal travel

[John Plum]

More symptoms:
The kick back in the pedal and noise

fades a little after prior braking, and...
occurs more toward then end of the pedal travel..or with firmer braking.

[John Plum]

It's very disappointing. I 'm a bit stumped.
The noise is like rattling and popping, and rapid, or even knocking. It's quite loud and reverberates through the cabin I think, though I'm not sure what it is. I'm beginning to think it's something more mechanical. The noise matches the kick back in the pedal, but varies in loudness, and does seem to fade with use a bit, but definitely not for long.

As for hydraulics, the hydraulic pump is loud at idle, I think ticking too much , a mechanical squeal as well, goes quiet with acceleration. I have few hydraulic pipe seals on order for sealing slowly seeping pipes, one for the main pipe to hydraulic pump and a couple for the rear height corrector.
Where should I start next I wonder?

[citronut]

how did you go about the bleeding job (bleeding the brakes ) John,

regards malcolm

[Featch]

As I suggested earlier, have you checked the condition of the flexible hoses? A weakened hose that bulges under pressure can cause this exact set of symptoms. Hard to spot but it happens.

Andy

[CitroJim]

Yes, it sounds like there is a lot of air in the system. A good bleed and intense citarobics are recommended.

John, the pump will be noisy when it is working hard to recharge the accumulator. Don't confuse this noise with the regulator tick. Pumps are noticeably more noisy on petrol engined cars because you don't have the diesel clatter to drown it out.

Your problem is also indicative of a flat accumulator. Listen for ticks from the pressure regulator and if they occur at more than 30s intervals. the accumulator is duff or you have a heavy internal leak somewhere. Also, once up to pressure, the pump should spend most of it's time running silently as it'll be effectively idling, just returning fluid back to the reservoir. The ticks you hear from the pressure regulator is the sound of it cutting in when the accumulator needs a top-up. You should hear the pump labour for just a few seconds whilst it builds pressure and the regularor cuts out and then it should go quiet again until the cycle repeats again, no sooner than the aforesaid 30s. A constantly labouring pump is very indicitive of a flat accumulator or a heavy leak. It will also make the pipes weep at their seals too as apart from being a reserve of pressure, the accumulator also works as a hydraulic damper to even out the pressure pulses in the system.

Another thing that can cause the brakes to feel and act strangely is if someone has replaced the spring link between the brake pedal pendant and the dosuer valve with a solid rod. It is a popular mod that sharpens up the pedal response but it does not suit all. On some it does have undesirable (in my experience and opinion) consequences. The spring can be found in a black tube that sticks out at right angles behind the pedal and rests on the head of the dosuer valve. Lift the pedal up has high as it will go, feel for the tube, pull it out and split the tube apart by releasing the collet in the middle. You'll either find a big spring or a length of 15mm copper water pipe inside.

[John Plum]

What kind of noise would lower suspension mountings make
Would it boom a bit, and be rapid under braking?
I'll have to check them properly anyway.
Alternatively, can I rule out the automatic gearbox ? Free de-acceleration is fine though.

[John Plum]

Sorry Guys, I missed your posts as I began mine.

@Featch: I have the hose check on my list: they looked OK but need to be to investigate by being rougher technique.

@ Citronut: I used a self-bleed kit, and just let some out into a bottle, but not so very much. It is a bit brownish (the filter is spotless!), and I have it on my list tomorrow to get replace, and do a complete bleed. Looks like I should do it with an accumulator too.
@CitroJim. AH yes, It's the accumulator, I was beginning to pay closer attention to the spheres and LHM at this point, so mentioned the noise, because all that had become hazy to me, since I sorted the BX thoroughly. (I did replace that pump there, because of the bearing noise..amazing how they run on). Probably should replace all spheres now, along with LHM.


I am very much heartened again. I will also check the lower suspension bushes tomorrow. Thanks a lot for being so quick and direct with the help here.
John

[Sl4yer]

John,

I'm sure I've read on here before that the back brakes take A LOT of bleeding, since the line goes from the wheel to the doseur valve (at the front!) and back again. Was a figure of 1/2 pint mentioned (from memory)? Might be worth bleeding a bit more until the fluid is the same colour as that in the reservoir. And then topping up.

James

[citronut]

John you missed my point on how you bled the brakes, all you need to do is with a clear tube attatched to one of the bleed kniples and the other end in a container, and with the kniple open,engine running, press and hold the brake pedle till you get a good stronge flow of citro blood, no close that kniple and go on to the next,

i was asking if you had used the above method

and not the up down,up down,up down,up down,up down,up down,
up down, method

regards malcolm

[myglaren]

If the LHM isn't a good, strong, green then it would probably be advisable to run some hydro-flush through the system then renew the LHM in a month or so.