*edited* Brakes sorted, thanks all, especially RRB!

[Iain C]

Right, here's what I've done so far.  Truck is a 1995 Disco 300Tdi, no ABS, and with just one brake pipe to each caliper.

Rebuilt 3 out of 4 calipers with new seals and pistons, the only one I did not rebuild (nsf) was fine.  During this, the master cylinder ended up empty.  New discs and pads fitted all round.

Bled master cylinder by filling with fluid, 5 slow pumps up and down, wait 10 seconds, same again.  As I understand it to do this, no bleed nipples need opening.

Then I have tried to bleed calipers in the following order, nsr, osr, nsf, osf.
I bought an Eezibleed kit and ran it off a trailer tyre, but for some reason there was not enough pressure to make the fluid come out at any more than a pathetic trickle.  So I got SWMBO to help, and did the old open the nipple, pedal down, close nipple, pedal up etc catching the stream (without a hose because it's freezing and won't fit) in a jar.

I then tried again today, connecting the Eezibleed to a car spare that should have easily had enough pressure in it, but again just a trickle.  So I left the eezibleed connected (it seemed to have plenty pressure in to keep the master cylinder reservoir topped up) and got SWMBO to pump the pedal again.

It is marginally better but still not good enough.  Today each caliper had at least 10-15 pumps of fluid pushed through, and the fluid is running clear and bubble free.  If I use the brakes and then have another go 15 seconds later or so, they feel perfect, leave it for a minute and the first pump is not right.  Pedal goes about an inch further (which feels a lot) on the first push, and then the brakes are fine again.

It does not seem to be pulling in either direction, I've now flushed through nearly 2 litres of fluid, and as far as I can tell there are no leaks anywhere, pedal does not dissapear into the carpet if I keep the pedal pushed in for a long time.

To be honest I'm at my wit's end with this now, am I doing something wrong?  Shall I try the Eezibleed on a tyre which I absolutely know is at 20 PSI or so and just flush another litre through?  Does it need bleeding on a steep slope or something?  I noticed somthing that resembles a bleed nipple but has no hole on it on the rears, do I need to open this at all, or perhaps slacken off some union somewhere?

Any tips would be really gratefully appreciated!

[Range Rover Blues]

Ok, a couple of things.  Firstly it sometimes helps to bleed out of the pipe to master cylinder unions first if there's lots of air.

Now if the pedal feels spongey then it's air, but if it's roack hard (with the engine off) then you've done it right.  It will be spongey witht he engine running, that's the callipers flexing :shock:  stop doing that .

If you have rebuilt 3 of the callipers then obviously the rubbers will be new.  The rubbers in a calliper are the only "return spring" and as the piton extends they deform, when the pressure is released they pull the piston back in a little.  

As your rubbers are almost all new it wil have changed the feel of your brake pedal somewhat, this is normal.

[Iain C]

Thanks for the tip RRB but the feel is not consistent.  Surely the pedal should move the same amount before the anchors come on each time I press it, not a different amount depending on when I last used the brakes?

And with brand new discs and pads all round, the pistons will be hardly moving on the return anyway?

When I tried driving it during the week, the pedal went a scarily long way down before anything happened on the first push.  Bleeding it today has got rid of some of this travel, however there was no obvious air coming out at any time.

Engine off and it does feel rock hard and I cant notice any difference in pedal travel, but engine on the feel just does not seem consistent.  It's the same thing, if I have not used the brakes for upwards of 30 seconds the pedal goes further on the first push, if I have just used them the pedal does not need as much of a push before the brakes start to work.  Before I rebuilt the brakes the pedal felt fine and always the same (even though discs and pads were in a sorry state).  

Where you say "firstly it sometimes helps to bleed out of the pipe to master cylinder unions " what exactly do you mean?

[Range Rover Blues]

Where the brake pipes go into the master cylinder, you can sometimes get air out by slackening the unions as though they were a bleed nipple.

Now, the variation in travel.  Did you set the wheel sbearinsg properly?

Are you sure?

A slight play in a wheel bearing will cause the disk to "run out" under cornering etc, this pushes the pistons back into the callipers.  Again because yours are all new..........

[Iain C]

I was pretty sure that I'd set them right, presumably there would have to be some pretty dramatic play in the bearings for it to be that bad.  I'll jack up each end and grasp the wheel and make sure though.

That said, with brand new discs and pads all round that have done about 5 miles, there should not be much scope for the pistons to really move at all anyway presumably?  I had to push them all the way in to get the new pads in...

The one thing I am a bit worried about now you mention wheel bearings is the hub seal...I put them in flush (as they were before) but I now hear that they need to be in a further 4mm.

But if the wheels were that far out presumably you'd feel it...apart from the brakes I'm amazed at how nice it drives now...

[Iain C]

And thinking about it, some brake bleedery today has got the pedal from downright frightening to just annoying on the first push, with no change in anything else...

[Range Rover Blues]

If you don't have the seal right in then the lip onto the radial face will be worn away already, but whilst it's there it can make setting the backlash very hard.

f you've improved things again by bleding then that's probably your problem, or at least the biggest part of it.

[Ralph]

It will fell much better after the discs and pads have beded in tho this may take a few hundred miles or more dependent on roads driving style etc
Something that somtimes happens is that when bleeding brakes by pushing the peddle you will tend to push the peddle right to the floor. Now although this is a perfectly good way of bleeding it pushes the piston in the master cylinder way beyond where it would go during normal use. What i have found is that some master cylinders have had rust in them at extremes of piston travel which then damages the seals causing problems not unlike yours.
Maybe worth you taking the master cylinder off the servo and looking checking to see that no fluid has leaked past the seals.
What i suggest is that when bleeding brakes using the peddle is to only push it half way down each time.

[bilge rat]

another little tip . iff you clamp off all the flexis, then remove one at a time fronts first see which one makes the most difference, i know the back is linked but you may be able to pinpoint the problem better. iff the engine is off and you pump the pedal till it goes hard , wait about 10 secs then put your foot on the pedal and its dropped its usually a sure sign of air somewhere. alan.....

[bilge rat]

another little tip . iff you clamp off all the flexis, then remove one at a time fronts first see which one makes the most difference, i know the back is linked but you may be able to pinpoint the problem better. iff the engine is off and you pump the pedal till it goes hard , wait about 10 secs then put your foot on the pedal and its dropped its usually a sure sign of air somewhere. and dont press the submit :oops:  button more than once alan.....

[Iain C]

She's sorted!

Went for a test this morning and thought about it objectively.  It was not the time between pedal presses, it was how much steering had been going on!  Out of a roundabout and the brakes were bad, 1 mile straight run and they were not too bad.  It was obvious that RRB was on to something with my hub, and as right handers were the worst, my money was on NSF.

Got home, gave it a wobble, still on the ground, and it felt very bad!  Jacked it up and I'm surprised the wheel stayed on really!  As soon as I took the dustcap off I remembered the endfloat shims that I had not been able to get back on (different thread), so I changed the seal (mangled!) and put a new wheel bearing in for good measure and she's as right as rain.

I checked all the others and they seem fine, however according to this picture from LR4x4.com, I put the NSF hub seal in the wrong way round first time.
 


By the looks of things, the pokey up inner piece needs to be pointing inboard, towards the diff, not out towards the wheel.  I'd done it with the "smoother" side facing inboard.  Problem is, I have a horrible feeling I may have done the same on the other hubs too, as I copied what I was taking apart.  Which could explain why the back wheel bearings were full of crud?

They obviously have not gone back together so badly that the hub endfloat is affected, but I'm worried about stuff getting in or out.  Is it just a case of keeping an eye on it and if I can't see any oil anywhere it's probably OK or shall I bit the bullet and strip them all...again...

Big thanks to Range Rover Blues for putting me on the right track...bit odd that with some more bleeding they had got a bit better, I reckon there was still air in there too...just to trick me!

[Range Rover Blues]

A golden rule with oil seals is that the little spring holding the lip against the shaft (looks like a silver worm) is always inside the oil you are trying to keep in.  If you look at the oil seal and think that any pressure in the oil will cause the lip to be forced against the shaft whereas any vacuum will cause air to be drawn in.