CorwinB

Right, here's the end of the story. It was the brake vacuum pump that was broken, only been fitted 2 months but goes to show I should not have discounted its failure. Wasn't even a Br***art component! New pump fitted and we are back to good brakes, although I do need to adjust the push rod again to move the bite point to a better position. A bit of a relief! Thanks to all of you for your help.

Apparently it's supposed to create enough vacuum to stick the pipe to your finger, whereas I was having to hold my finger to the pipe. It was enough to pull my finger on to the end of the pipe, but the slightest effort would take it off.

I ended up giving the landy garage a call and went there after work yesterday. I had not tested a healthy vacuum so I did not know what I was meant to be comparing it to. When he tested the vacuum on the pipe, there was not enough, which points to the (new) vacuum pump (or the cam, which is more expensive so I hope it's actually the pump that's failed). Going to take it in on Friday to get a new pump fitted and to check the cam.

Hmmm. I have tested again this evening, the servo test does not make the pedal dip when I start the engine, so I suspect all I have done is to move the bite point. Moving the car back and forth and applying the brake, it doesn’t feel like it is ‘biting’ down on the discs properly. It’s quite easy to overpower the brakes with the clutch. Might try swapping the non return valve for the old one (edit: did this to no effect)

Hello western, thanks for the advice so far. I removed the unit, then the push rod on the new one has an 8mm hex head on the stem of the push rod, and a dome headed 6mm nut on the end. I was able to get a spanner on the stem, hold it with pliers, and wind out the dome headed nut by about 10mm (did initially adjust it to 5mm as the original had a 5mm gap). Oddly the older booster does not have this, just a dome headed nut on the end of the stem. The new brake booster is also much deeper than the old one. What this has done is raise the biting point of the brake pedal up to near where it was before the first booster went kaput (after fitting the second booster the biting point was much further down than before). I now have a lot more braking force with less pedal effort than when the old booster was broken. I am still not certain if this has fixed the issue, or masked the problem, because..... Did the servo test. Pumped brake pedal which felt stiffer (though not rock hard). Started engine, thought I could feel movement but maybe I was subconsciously pushing harder. Emergency braking test from 40mph much better as I am able to exert more brake force. Started to pour down so packed up for today. More testing required I think.

Hi western, thanks for the swift response. Were your symptoms the same (basically having half/quarter braking power that it should do)? If so, how did you adjust the pushrod? EDIT: I've given it some more thought and it does make sense, as I know for sure that the old booster was broken (as changing it for the new one got rid of the stiff brake pedal issue), and it would be odd for the booster and the MC to break at exactly the same time as the brakes were totally fine before the booster/stiff pedal issue. I found this post on how to adjust the pushrod (albeit for a disco 1) so will try that: https://www.aulro.com/afvb/discovery-1-a/209538-brake-misery.html

Hi all, I hope I can draw on the hive mind's experience with this one before it costs me a fortune to fix. I have also posted this on LandyZone but would like to appeal to you too. Car is a 1996 300TDi 110 Brakes on this were great and could stop big heavy trailers, lock up the wheels etc. no problem until last week. On the way back from the Dordogne, as we got to Normandy for a few days camping, the brake pedal went very stiff and it became hard to stop, needing almost double-footed effort to stop. The vacuum pump was replaced a few months ago, but I popped the vac hose off and tested it with my finger while the engine was running and it still sucked my finger onto the pipe. Some googling of various forums on my phone pointed towards the problem being the booster. Ordered a new one from Bearmach and fitted it (including the new o-ring between Booster and Master Cylinder). Now there is a different problem - lack of braking force. Whereas a month ago the car would stop fine, then a week ago the pedal was stiff all the way down, now there is very little braking force at all and it's really hard to stop the car. A test of an emergency stop from 40mph on wet tarmac (which would previously have locked the wheels) required far more room to finally stop and was quite scary in the lack of braking force. Fluid level in the reservoir seems the same as before, I did not open up the hydraulic system when I changed the booster. Here's the odd thing - when braking in reverse, the stopping power and brake effort seems much more similar to how it was originally (ie. good). The amount of brake pedal travel to make the brake system start working is much more than before, and it feels spongy. I've read a lot of threads on this but not found many people who actually had the same sounding problem and went on to solve it. I have tried to do this test: 1. With engine off, pump brake pedal until it goes hard 2. Start engine with brake pedal held down to see if pedal moves. BUT the brake pedal just does not go hard at all, nothing seems to change. My mechanic friend suggested the master cylinder could be at fault. No evidence of brake fluid leaks in the pipes as far as I can tell. Has anyone had experience of this? I am loathe to start replacing bits willy nilly without a good steer on the likely cause. Many thanks