Vehicle & Technical > Discovery

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

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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 :wink: .

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...

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