Blakes deteriorate after bleeding.

I let my brake fluid drop below the minimum line way back and I think that got air in the system. I topped up reservoir and bled them and all went well, pedal went hard and they worked fine for a day. The next day pressure had dropped and required a few pedla presses and over the next couple of days it dropped to needing about 15 quick pedal pushes to get any decent stopping power. At this stage it seems to settle and gets no worse.

I have now bled the system 4 times on seperate occassions and each time they get pressure immediately after bleeding but proggressively decline until they settle at about the '15 pedal pump for pressure' mark and then stay steady.

When bleeding most recently I have struggled to ever get rock hard pressure on one push whereas the first couple of times it did allow me to bleed and achieve excellent hard pedal on one push.

As stated, this all seemed to start when I let the fluid drop but I am starting to wonder if something beyond just air in the system is the underlying fault and the temporary low level of the reservoir was just a coincidental red-herring.

Does anyone have any experience of this specific symptom (I didn't see any from search)? If not I guess I have no choice but to start overhauling the brake system now.

sounds like the master cylinder has had it because of age and pressing the pedal down all the way till it stops due to bleeding the brakes there will be rust and crud at the bottom of the master cylinder where the piston doesn't normally work that has torn the seals. so looks like you need a new master cylinder.

graham
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98 d1 300tdi auto.

aye you have killed the seals in yer mastercylinder time for a new one

yeh I second that but does anyone know if theres a chance of re sealing ; not done this on a landrover before; but is it possible?

You can get re-seal kits, they don't always work, and if the piston bore is Borked, then it'll just eat them again......

Bugger!

..Although glad it's such an absolute diagnosis so hopefully I can fix it easily

They aren't too expensive to buy new - even the proper Girling ones - but they can be a bit of a pig to fit.

Any tips for fitting Oxides?

So I understand fully, was the ripping kind of unavoidable? I mean, if I hadn't let the fluid run low then I wouldn't have had to bleed brakes or use break lever right to floor so perhaps in that respect it was avoidable. But I mean, accepting that I should be able to bleed the breaks without ripping the seal was it just that the cylinder was so old it had amalgamated all the rust/crap and that a newly fitted cylinder should allow me to make similar mistake/bleed brakes in future without an issue for a good few years?

Yes, probably old age had a lot to do with it. The land rover manual has a good description of how to replace the master cylinder.
pdf Land Rover Manuals | Landroverweb.com

Just to finish this thread, I replaced the master brake cylinder and it did indeed solve the issue. Thank you again for the excellent advice.

For others who may be in a similar situation, it was not too difficult a job. However, I did find I needed two socket wrenches (one smallish) to be able to undo the second bolt under the cylinder.

Also a warning for anyone as inexperienced as me. Having replaced the master cylinder I bled the brakes and got a rock hard pedal rolleyes and also didn't fully adjust the height of the brake pedal correctly when putting it all back together. Driving round the M25 the following day I had smoking pouring from the wheels and enjoyed a lovely burning smell. I'm not sure if I had made the pedal too hard or it was pressure on it through the incorrect height adjustment but the hydraullic pressure was obviously building as I was driving until the brakes were permanently on. I let some high pressured squirts out (double ) from one of the bleed nipples and adjusted the brake pedal height at the same time and now I have a nice amount of travel in the brake pedal whilst still being able to effectively stop the vehicle and no more driving along with my brakes on