citroen dispatch brakes

[rainydays]

replaced a corroded section of brake pipe, one new front calliper and new front brake pads on my 1.9D 2000 reg dispatch.
Tried bleeding my brakes but i am now having problems. The brakes seem to firm up but when i start it up the pedal becomes really soft and travels to the floor. There does not seem to be any more air the system so i am now stumped.
Anyone any ideas/suggestions. Much appreciated

[the_weaver]

What make of caliper is it? Does it have a single piston, and a sliding caliper? If so, have you checked that the caliper is sliding ok on it's slides? Sometimes the calipers can lock up on the slides. It's easy to check, just remove the brake pads, and move the whole caliper backwards and forwards with your hands.

I've just been working on the Bendix brakes on my ZX. If you've got Bendix, then they can be a bit of a pain sometimes. When I bolted my caliper on, a few times recently, whilst experimenting with it, I noticed that sometimes it would lock up. I think it might be to do with the centering of the sliders in the bores. You should tighten the bolts bit by bit, whilst moving the caliper along it's slides. That's the method I've found best. Also, support the caliper's weight with your hand, as the bolts are tightened.

Are the brake pads moving ok? Sometimes they can be a bit tight, with old rusty calipers/pads. They should be ok if everything's new.

I've noticed that a small problem at the brake pads can cause a lot of travel at the brake pedal. So, if something is keeping the pads away from the disc, it can feel like a lot of travel on the brake pedal.

New pads will feel a bit funny for a few miles. They do need to bed in for a few miles. However, your problem sounds worse than that.

Could it be rust, on the outer edge of the brake disc? Check that the brake pads are not sitting up, on the rust on the edge of the disc. You can clean that rust off by rotating the disc, whilst holding a chisel against it.

Paul

[rainydays]

Hi Paul, thanks for the reply. There was some rust on the top of the discs but i had already cleaned this off.
The old callipers were Bendix but i replaced one of them as the piston was not moving.
Will have a another good look at it today and double check that everything is moving freely

[Carsten S]

Can you pump the pedal hard, and brake if you pump 2-3 times?
If so, your master-cylinder is broken, because it has been out in an area where it normally never operates.

On some models, you need a Lexia to force ABS-pump ON, to bleed the brakes completely (if there is air in the ABS-pumphousing of course).

[rainydays]

If i pump the brake pedal it firms up then creeps to the floor if you keep the pressure on the pedal

[myglaren]

If i pump the brake pedal it firms up then creeps to the floor if you keep the pressure on the pedal

That sounds like weeping master cylinder seals, which Carsten has indicated could be the problem but could also be the ABS not bled through.


I was advised when tinkering with ABS brakes to open the bleed nipple prior to starting and allow fluid to escape that way rather then it being forced back into the system when pushing the pistons back into the bores to accommodate new pads.
It was said the allowing the fluid to reverse-flow, particularly the mucky stuff that lives in the calliper, can ruin the ABS operation.

[Dommo]

If i pump the brake pedal it firms up then creeps to the floor if you keep the pressure on the pedal

I'm sure I read somewhere that this is normal behavour for diesels... Can't remember where I found it though but its to do with the vacuum pump (as apposed to the vacuum being produced by the inlet manifold pressure)

[the_weaver]

If you do find that the caliper is not sliding, then make sure that the sliders are sitting flat on the mounting face of the hub. There may be rust causing the slider to lean over a bit, and touch the sides of the bore.

Dommo, I heard that as well. That the vacuum is so powerful that the pedal will creep. I don't know if they mean small (1.9) diesels in cars, or much larger diesels, like in lorries though.

When i had air in my brakes, the pedal had to be pumped three times to get any braking, but once the air was out, the brakes were ok.

Are you sure you've got the correct caliper for that side? The calipers are usually different on each side. They're not interchangeable. You can check, by having a look to see where the bleed nipple is. It should be near the top of the caliper, rather than near the bottom of the caliper. Air rises, and is bled out from the top.

Is the caliper brand new, reconditioned, or from a scrap yard?

When you fitted the new pads, did you re-use the old metal slide plate that hold the pads in? If so, you should make sure you clean the rust off it, with a wire brush or emery cloth. That rust build up can make the pads tight, and stop them moving properly.

Paul

[the_weaver]

"Diesel creep" is what Dommo was referring to. If you google for it, you can find a lot of information.

I don't know whether you've got a real fault, or "diesel creep". However you can do some research on it, now that we know the name.

Try switching off the engine, exhausting the vacuum, by pressing the brake pedal a few times, then see if the pedal creeps downwards.

Has anybody else experienced this creeping pedal on the 1.9D?

Paul

[Dommo]

"Diesel creep" is what Dommo was referring to. If you google for it, you can find a lot of information.

I don't know whether you've got a real fault, or "diesel creep". However you can do some research on it, now that we know the name.

Try switching off the engine, exhausting the vacuum, by pressing the brake pedal a few times, then see if the pedal creeps downwards.

Has anybody else experienced this creeping pedal on the 1.9D?

Paul

My 306 does it which is a 1.9TD XUD engine, with a vacuum pump. That's what made me search about it in the first place a few years ago. However I only noticed it doing it after a bleed, which could be related but it could well be that I'd just never stood on the brake pedal hard enough before which I think is more likely. I fitted GTi-6 brakes to it you see at the same time, they're rediculously powerful and relentless but make you inclined to properly stamp on them and trust them to do some late braking, unlike the original brakes which were awful. If I remember rightly it doesn't sag to the floor when the engine is off.

Xantia owners will never experience this as the brake system is totally different.

[CitroJim]

Xantia owners will never experience this as the brake system is totally different.

Very true Dom... If our brake pedals creep to the floor then we have major issues. Very major ones...

Diesel Creep - you learn something new every day

Basically, on conventional brakes if you exhaust the servo vacuum then the pedal should go rock hard very early in it's travel. Start up with your foot hard on the pedal and it should sink a short distance - that's the accepted servo functional test.

[rainydays]

I double checked things today, removed callipers again and scraped off quite a bit of rust debris and re-bled. brakes are now operational again although they do not appear to be as sharp as they were before i changed the calliper. Might need a bit more bleeding but i will let them bed in first i think.
Many thank`s for everyones input, much appreciated.

[Dommo]

I double checked things today, removed callipers again and scraped off quite a bit of rust debris and re-bled. brakes are now operational again although they do not appear to be as sharp as they were before i changed the calliper. Might need a bit more bleeding but i will let them bed in first i think.
Many thank`s for everyones input, much appreciated.

Brakes that aren't bed in yet will feel not sharp (blunt? ) so that sounds fairly normal. If they don't sharpen up soon something is wrong.

The only way we could have that issue Jim is with a slowly failing spring on the xantia pedal setup. Although I've removed that and love the feel of proper Citroen brakes