Spongy brake pedal

[BathurstTom]

Hi all the tech people here, I have a question for you regarding Brake servo units on 1998 Discovery 1 300TDI. I have read many examples on here of boosters failing and the lack of power assistance creating the need for extra pedal pressure needed. This I understand.

But I have also read other examples of the booster and/or vacuum pump having problems causing a spongy pedal. In these cases, without the engine running you can pump the pedal 4-5 times and the pedal becomes hard, but when the engine is started, the pedal can go to the floor. Is there a "disconnect" between the rod attached to the pedal and the rod that goes into the master cylinder? How/why can this sponginess happen?


Thanks,
Tom.

[disco 3 door]

As with all power brake systems with the engine off you will only get a hard pedal, even on a brand new vehicle. Is problem spongy pedal or excessive play.

Sent from my GT-N8020 using AULRO mobile app

[BathurstTom]

As with all power brake systems with the engine off you will only get a hard pedal, even on a brand new vehicle. Is problem spongy pedal or excessive play.

Sent from my GT-N8020 using AULRO mobile app

Spongy - will slowly sink to the floor with engine running. Seems to be vacuum related. Vehicle has been manually bled, power bled and vacuum bled, new master cylinder, proportioning valve and the wheel bearings are ok. Brakes pump up hard with no engine running and sink a little when engine started.

A couple of other examples on this site.

http://www.aulro.com/afvb/discovery-1/130129-spongy-brakes.html


http://www.aulro.com/afvb/90-110-130-defender-county/124678-bleeding-defender-brakes-any-secrets.html

There are dozens of examples like this on the web. I just want to know how a vacuum pump/servo problem can cause spongy brakes.


Tom.

[wrinklearthur]

Hi Tom

Is your brake system ABS ?
.

[bee utey]

Brake boosters have a small amount of slack between the pedal end and the master cylinder end, to operate the vacuum valve. Once the valve has been activated all the sponginess will be in the hydraulic system. A slowly sinking pedal is often a faulty seal on the master cyl secondary piston, allowing fluid to bypass the seal at low pedal pressures. Other than that I would be looking at flexible brake hoses for weeping/air entering the system.

[BathurstTom]

Brake boosters have a small amount of slack between the pedal end and the master cylinder end, to operate the vacuum valve. Once the valve has been activated all the sponginess will be in the hydraulic system. A slowly sinking pedal is often a faulty seal on the master cyl secondary piston, allowing fluid to bypass the seal at low pedal pressures. Other than that I would be looking at flexible brake hoses for weeping/air entering the system.
I suspected there was a gap between the pushrods. The master cylinder is new and has been checked. I have new flex hoses for the front and caliper kits (pistons and seals). But the main problem is the sponginess. I am pretty sure that there is no air in the system. I will look at the servo and vacuum pump.

Now that I know that there is a gap between the pedal end and the MC end I feel a lot more confident that I can diagnose and fix it. I couldn't understand the problem as I thought there was no gap and I couldn't get my head around it.



Hi Arthur, it is ABS - I have replaced the ABS module too :). I can actually get the ABS working if I can pump the brakes a few times.

Many thanks for advice - very helpful.

Tom.

[wrinklearthur]

Hi Arthur, it is ABS - I have replaced the ABS module too :). I can actually get the ABS working if I can pump the brakes a few times.

Hi Tom.

My workhorse at the moment is ( 'Fred' ), a 300TDi man D1 with ABS, it will do until I get the Defender back on the road.

'Fred' has the exact same symptoms as yours with the spongy feeling pedal ( but only when the engine is running ) and I was loath to start repairing it from the wrong end first, so I have been watching with interest this thread and it's links to other threads.

From the descriptions on the other threads and as I do have a good spare master cylinder, that will be the first spot I am going to try.
.

[BathurstTom]

Hi Arthur, the car has been to all four x 4 in Newcastle, and they tried another new master cylinder and it made no difference. I will be replacing the caliper seals and pistons and the front flex pipes and then looking at the vacuum system (pump and servo).

I am not inexperienced with brakes and this has had me foxed until bee-utey let me know that there is a gap between the pedal push rod and the master cylinder push rod. I know that when the engine is not running, the brakes will pump up hard and stay that way for some time, so I am confident in the hydraulic.


I have spent many hours reading of similar symptons on other land rover forumns, and I think that I can fix this now. As I am in Bathurst and the car is in Nelso Bay, it has been a long drawn process to get anything done, but I hope to get up there again in 2-3 weeks and go right over it.

I will let you know how I go.

[disco 3 door]

Spongy pedal = air in system. Vacuum leak = hard pedal . When you pump the pedal about 5 times with engine off you will run out of vacuum. This is why when you start the engine the pedal becomes softer or spongy.

Sent from my GT-N8020 using AULRO mobile app

[wrinklearthur]

The other day I made a comment about starting the wrong end first, at the MC. :p

So now I am instead going to inspect the wheel bearings and change the bearings and seals as required and I bet that fixes the problem of a spongy pedal in 'Fred'.
.

[Hopton1973]

Sorry to ask the same question but I have a spongy pedal and after pumping several times does NOT go hard. In an emergency stop only one wheel locks up.
I have put on new calipers recently and new pads and bled the brakes with no air in system. I couldn't figure out from the post whether it is the booster or main cylinder?? Thanks in advance

[BathurstTom]

Hopefully going north again to look at it. A few ideas to test. Will let you know.

Tom.

[disco 3 door]

Sorry to ask the same question but I have a spongy pedal and after pumping several times does NOT go hard. In an emergency stop only one wheel locks up.
I have put on new calipers recently and new pads and bled the brakes with no air in system. I couldn't figure out from the post whether it is the booster or main cylinder?? Thanks in advance

Booster problem will give you a HARD pedal

Sent from my GT-N8020 using AULRO mobile app

[BathurstTom]

Booster problem will give you a HARD pedal

Sent from my GT-N8020 using AULRO mobile app

Thank you for your advice. You also previously stated that there was air in the system. Please take the time to re-read the topic. You will see that the system has been manually bled, pressure bled and vacuum bled - several times. I consider myself very competent in this area, having been working on brakes for around 38 years, including motorbikes, cars and heavy vehicles (semis). I also consider that all 4 x four in Kotara are capable, they have also gone over this vehicles brakes.

I politely suggest that if you do not have a constructive answer to the problem that you refrain from inferring that people are wrong.

Thanks,
Tom

[wrinklearthur]

The other day I made a comment about starting the wrong end first, at the MC. :p

So now I am instead going to inspect the wheel bearings and change the bearings and seals as required and I bet that fixes the problem of a spongy pedal in 'Fred'.
.

Before I started to restore the brakes on 'Fred', I had the computer faults read then reset and the test came up with two faults;

The brake light switch was shown as open ???
The ABS sensor on the Front LHS is too high, this will need exploring carefully.
The weather here isn't too good and the shed is full of stalled project. :thumbsdown:
.

[BathurstTom]

Yes, I had the sensor problem. That was a simple fix, just pulling the sensor out, cleaning it and gently tapping it back in until it was seated. I know my problem isn't wheel bearing related, they are ok at least.

I have a few new ideas to try in regards to testing the vacuum pump and the booster. Hopefully will be in Port Stephens this weekend (I so wish it was in my backyard - it would be going by now). :)

I will be going armed with new rear rotors, front brake lines and a complete set of caliper pistons and seals as well as as my pressure bleeder and hand held vacuum pump.

I will let you know how I go.


Cheers,
Tom.

[OlliesLRover]

Thank you for your advice. You also previously stated that there was air in the system. Please take the time to re-read the topic. You will see that the system has been manually bled, pressure bled and vacuum bled - several times. I consider myself very competent in this area, having been working on brakes for around 38 years, including motorbikes, cars and heavy vehicles (semis). I also consider that all 4 x four in Kotara are capable, they have also gone over this vehicles brakes.

I politely suggest that if you do not have a constructive answer to the problem that you refrain from inferring that people are wrong.

Thanks,
Tom

And yet you still have a problem.

You start a thread asking for assistance and then deride someone who offers same, based on your interpretation of his posts:censored:.

Good luck with the problem.

[BathurstTom]

Too wet to get much done so I took the calipers off and brought them home. New pistons and seals installed. Will fit them when I go up next time...


Tom.

[wrinklearthur]

I have been talking to a couple of Disco owners down here and they have told me, when bleeding the brakes to disconnect the battery to disable the ABS module.

Tapped the LHS front wheel sensor down and now the ABS light goes out and stays off. Good!

Pumped the brake pedal with engine off, the pedal goes hard and doesn't sink at all. Then started the engine with the pedal held on, the pedal goes down with the vacuum to about halfway, but now it feels spongy and wants to slowly keep sinking to the floor. Bad!

The tests were done without moving the vehicle, so I am thinking there are some lines that may still have air in them, by not moving the vehicle should rule out any possible slackness in the wheel bearings .

I was going to pop the bonnets of our two Discovery today and compare the differences of the two types of master cylinders, but I ended up changing tyres and photographing a threesome of Blue tongue lizards. Tomorrow now.

Got a quote from a brake service in Hobart for a ABS brake mastercylinder about $260, that's a lot better price for the same thing off fleabay.

.

[BathurstTom]

Hi Arthur, I knew about disconnecting the battery. That's in the manual. One of the things all4xfour said was that the calipers may be sticking. Having pulled them apart today, one back one may have, but the rest looked fine. They're now reconditioned. Will be going back up next week and I have a few days off to sort it out.

I'll let you know how I go.

I am still suspecting the booster - especially the valve in the back of it.

Cheers,
Tom.

[snowbound]

Yes, I had the sensor problem. That was a simple fix, just pulling the sensor out, cleaning it and gently tapping it back in until it was seated. I know my problem isn't wheel bearing related, they are ok at least.

I have a few new ideas to try in regards to testing the vacuum pump and the booster. Hopefully will be in Port Stephens this weekend (I so wish it was in my backyard - it would be going by now). :)

I will be going armed with new rear rotors, front brake lines and a complete set of caliper pistons and seals as well as as my pressure bleeder and hand held vacuum pump.

I will let you know how I go.

Cheers,
Tom.
I just renewed my hydraulic clutch. Bleeding pain in the ****

[wrinklearthur]

I just renewed my hydraulic clutch. Bleeding pain in the Slave Cylinder :p

Reverse bleeding works well on the clutch.
.

[disco 3 door]

Too wet to get much done so I took the calipers off and brought them home. New pistons and seals installed. Will fit them when I go up next time...


Tom.

Did you check the pad slides for wear, as had two calipers wear to the extent the pad drops & sit on rotor. One was 12 monthes after rebuild & onces prior.

Sent from my GT-N8020 using AULRO mobile app

[BathurstTom]

The pads are nearly new - though they are aged, there is plenty of meat on them. Once I sort the main problem out they will be replaced though.

Cheers,
Tom.

[wrinklearthur]

Bench bleeding master cylinder.

How to - Bench Bleed a Brake Master Cylinder - YouTube

At one point the operator mentioned that damage can occur if the plunger is pushed in too far.
.

[wrinklearthur]

I have been busy looking at the pro's and con's of pressure bleeding as compared with vacuum bleeding.

Now I'm under the impression that vacuum bleeding is more likely to dislodge a trapped air bubble.

.

[BathurstTom]

Ok, I spent 4 days trying to solve the problem again. Fitted the reconditioned calipers. Pressure bled the system. I bled over a litre through each of the calipers and no improvement (and no air bubbles visible). Scratched my head and made up a hot wire to run the ABS pump and each of the valves in the module for multiple three to four seconds burst. Got a fair bit of air out of the front d/s caliper. Aha! Thought I had the problem solved! But no improvement. :mad:

I fitted a new booster for lack of other ideas as one of the causes of a sinking pedal is a faulty valve in the booster (see page 602 of the rave manual). No improvement.


My only idea now is that perhaps the brake line from the the master cylinder rear (primary circuit) to the abs module or the line from the abs module to the Proportioning valve may be blocked. This may explain why the system seems so slow to bleed. With the pressure bleed system at 20lbs'sq inch it does little more than dribble out.

When reversing the vehicle, the brakes are very effective - which I would think indicates that the secondary circuit is working. It has a very spongy pedal and minimal braking power going forward.

I think that perhaps if the line from the master cylinder rear is blocked, the system would still bleed, albeit slowly, through the secondary circuit. This would fit in with the symptoms. It is just unfortunate that I was already 80k's towards home (and not enough time to go back) when I thought of this possible cure.

Will be too busy to go back for at least a month, so the saga continues.


Cheers,
Tom.

[jazzaD1]

maybe the brake calipers are upside down?

[BathurstTom]

Nope, the calipers are right way up. Thanks for the suggestion though. I'm searching for ideas... :)

Tom.

[Sparksdisco]

Have you checked all your wheel bearings?

[BathurstTom]

Hi Sparksdisco, yes, the wheel bearings are fine.


Thanks,
Tom.

[wozzlegummich]

Spongy brake pedals in D1 will drive you crazy. I just wanted my D1 to pull up the same as a Pajero I owned of the same age. The pedal feel has never instilled what I would call "confidence" when jumping on the picks in an emergency situation. I haven't EVER been able to "lock em up" in the dry even when the ABS wasn't working. If I give the pedal a single "nervous" light pump before hitting them hard the pedal feel is great. It is just that initial application that is not the best. In my quest for the ULTIMATE D1 brake pedal feel I have...

Replaced the brake master cylinder
Replaced Both front brake calipers
Replaced frt brake rotors with slotted & drilled
Replaced all brake hoses with PFTE high performance
Replaced rear calipers
Had booster tested
Replaced pads with greenstuff
Numerous bleeding and pressure bleeding operations


Still searching for that brake pedal feel nirvana.

[BathurstTom]

Hi all, the vehicle is now in Bathurst. What I have found is that I can get some pedal when pressure Bleeding the rear brakes and following a Wabco procedure for bleeding a wet ABS module. Firstly pressure bleed the brakes starting with the longest circuit (Left Rear). Then cycling the outlet valve for 10 seconds whilst pressure bleeder attached, disconnecting pressure bleeder, waiting five seconds and then running the pump for five seconds. This is done four times followed by a pressure bleed. This was done for the raer brakes and I started getting reasonable pressure at the pedal.

All good so far. When I started this procedure on the front (primary circuit) I lost all pressure. What I found was that there was air in the front lines. No surprise there. But I cannot seem to purge it. I got my neighbour to pump the pedal a few times and I could hear a hiss coming from the Master cylinder, which I didn't expect. Upon investigation I could feel a draft coming form between the master cylinder and the booster at the top. Both the master cylinder and the booster are new and the o ring is in place.

Does anyone have any suggestions as to what would be causing this and what effect this would have. I suspect that this is the cause of my problems and I suspect that there is air entering the system some how (note that there are no visible leaks). Could it be the "grommets" between the reservoir and the master cylinder?

Sorry about the long post, but this is my final fling at this as if I cannot fix it at my next attempt, the vehicle will be parted out for spares.


Thanks in advance.


Tom.

[wrinklearthur]

If I can't find the problem soon then I will be wrecking the D1 as well ! :mad:

A brains trust think tank at my place today, Graham ( of Tumbling Tucker Truck fame ) and myself had a stripped down D1 master cylinder in front of us, not the ABS one as that's next.

The yellow cap that the actuating plunger passes through can be gently levered off to have a look in side the MC, thoughts are that if the rubbers between the reservoir and the top of the MC get hard they can still not leak fluid, but could let air be drawn in at that point, same with the first cups on the plunger in the MC.

The second plunger inside the MC had some very faint wear marks or scores in it and this could only come about by a small particle of rubbish coming down the feed hole from inside the reservoir and when the plunger is working the particle is scissored between the feed hole and the plunger.

At this stage My D1 looks like that plunger and the associated rubber cups could have similar score marks on them.

And Grahams project camper needs the Wabco bleeding procedure. Has anyone got a link to that site please?
.

[workingonit]

Re the hissing between master and booster - I appreciate you say the units are new and the o ring is in place. Hissing could be the rear most rubber reservoir mount is not seated/mated properly to an internal tube? These reservoir mounts are replaceable, but the rear one is a little tricky to connect. I gave up on my Wabco and took out the fuse. Reading your thread with interest.

[wrinklearthur]

New master cylinders are available

Ref;Land Rover Discovery Brake Master Cylinder FOR ABS | eBay (http://www.ebay.com.au/itm/Land-Rover-Discovery-Brake-Master-Cylinder-for-ABS-/200512969789?pt=AU_Car_Parts_Accessories&hash=item2eaf811c3d&_uhb=1)

The price from this supplier for this new unit is :AU $323.00 and freight, Postage: AU $19.80 Express Postage


http://galleryplus.ebayimg.com/ws/web/200512969789_1_0_1.jpg

--------------------------------------------------------
Ref; Land Rover Discovery 1`94 ON Brake Master Cylinder With ABS | eBay (http://www.ebay.com.au/itm/LAND-ROVER-DISCOVERY-1-94-on-BRAKE-MASTER-CYLINDER-With-ABS-OEM-/370575590480?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item564806c450&_uhb=1)

Another supplier with similar price, Price:GBP 132.50 Approximately AU $243.28
Postage: GBP 14.95 (approx. AU $27.45) Royal Mail International Signed-for,
some delay is expected when ordering from the UK.

https://www.aulro.com/afvb/images/imported/2014/02/759.jpg

Those prices are well priced compared with the price of a new rebuild kit which may not be successful due to wear within the cylinder.
I had a look online for prices for the ABS kit's, but it appears that they have been removed for sale at the moment from internet so unable to post here.
.

[BathurstTom]

When I get the time, I will block off the primary circuit (Master Cylinder Rear) and see what pressure I can get on the rear brakes alone. If that works, I will block off one of the front bakes at the ABS mod outlet and see what gives. I am getting so frustated with this, but I just know it has to be solvable...

Well I hope it is.


Don't hold your breath though, I am halfway through painting the house (inside) and have the lounge room and main bedroom stacked solid with all the furniture in the centre and the hall is full of furniture and the kitchen and dining room full of paint, plaster, benchtops and tools. I hate to say this, but my shed is cleaner. And we all know how bad our sheds get...:o

Wife comes back in about two weeks...:angel:
Tom.

[BathurstTom]

Well,today I used the two old front brake pipes to bypass the ABS modulator. I connected pipe that goes into the ABS for the front brakes directly to the pipe going from ABS to the Front Right Disc and I connected the pipe that feeds into the ABS for the rear brakes directly to the pipe that leads to the rear left and I now have pretty solid pedal. Doing it this way seems to have isolated the problem to the ABS module.

Unfortunately I could not start the truck to test it - I think I have the dreaded spider (or spyder?) problem. But I have never had this much pedal before and it is not sinking. Interestingly enough, on the way back from Lemon Tree passage I spoke to some NRMA mechanics whose mother had the same problem with a D1 and apparently the LR agent in Padstow bled the ABS with testbook for a cost of @ $400 and it now has perfect brakes.

Well I have an old ABS module here that is half pulled down, so I will pull it down some more to determine where the air is getting trapped inside and see what I can come up with. I know it would be easier to take it to an LR agent, and I would, except the nearest to Bathurst is Dubbo I think, and that is a two hour drive away unfortunately. Anyway, I will experiment with the old ABS module and some wabco documentation that I have and see what I can come up with.


Tom.

[BathurstTom]

I fixed the spyder problem a few weeks ago. Since then I have sourced the plug/loom that goes into the side of the ABS module. I now have a switch box so that I can control each inlet and outlet valve in the abs module. Just have to get time to follow the wabco procedure for bleeding the ABS module. If that doesn't work, it might be a gallon of petrol and a match :twisted:. No, once I get the time I am hoping that I can fix this. I have already had the pump going whilst cycling the valves and am able to hear and feel the ABS working when my foot is on the brake. Unfortunately I could not find the printout of the wabco procedure at the time and I did not follow the correct pattern. I have since found the printout - so wish me luck. If I do fix it, I will put some directions, pictures etc up. Here's hoping!

Cheers,
Tom.

[wrinklearthur]

I have been busy, too long a story to repeat on here.

Today the Wednesday visitor from Sawdust road, Bruny Island ( Tony ) came up, while in conversation he told me that his master cylinder reservoir is weeping through the grommets between the bottom of the reservoir and the master cylinder.

I had just the thing for him, and dragged Tony over to the worst kept shed in Tasmania.
I showed him the remains of a junked ABS master cylinder that I had scattered on the work bench, it's the one that gave me all the trouble in 'Fred' and now has since been replaced.

I pointed out how to remove a portion of the cylinder assembly to be able to have the reservoir come off, there is a small tube attached to the plastic front of the cylinder that has to be pulled back, so after that is out of the way the reservoir can be lifted up.

I also pointed out the little device under the ABS cylinder that is not found on the non ABS models, showed Tony that it needs to be removed to dissemble the cylinder completely and without a pentagon shaped bit to be able to undo it, that is the point where I left it, to get on with more important jobs such as chopping down a murdering tree.

Tony in his view said he should be able to make a good one out of the two cylinders and now treasuring the bits that I junked.

By the way, 'Fred' was treated to another bleeding session, which was mostly trapped air at the pipe junction on top of the ABS modulator and a new brake light switch brought off fleebay ( I have found out that you don't use the correct word as scammers can get information about your buying habits by searching for that word :mad: ), the old switch when pressed in by hand only had one distinct click, whereas the new brake light switch when pressed had two distinct clicks. Using the paper clip method to reset the fault code, 'Fred' now has brakes that are working great.

To fit a new brake light switch, the inner locking ring must be drawn out to the end of the fully extended plunger and the switch is then inserted into the correct hole in the bracket under the dash. Using smoke and mirrors with out hopefully the smoke, a lot of persuasive words, the switch fitted in place is then locked by pushing the ring thing back inside the protrusion and that then holds the switch in place. The pedal is then let gently back, the plunger when the contacts in the switch bottom out has a ratchet inside, this clicks on and stops when the pedal is fully returned to it's rest position.

[BathurstTom]

Well, I am defeated. The first time in my life I could not fix a car. That is the first and most definitely last Land Rover that I will ever own. It will be for sale shortly. What a waste of time and effort.


Tom.

[wrinklearthur]

Hi Tom

I believe that new master cylinder of yours is faulty, try and get hold of another known good one, swap them over and then go through the bleed procedure's once more. My old cylinder in 'Fred' was leaking internally between the primary and secondary brake circuits chambers back into the reservoir. After changing it out with a spare ABS master cylinder and then purging the brake lines of air, I am happy with 'Fred's' brakes once more and the pedal doesn't sink to the floor when vacuum is available.

Bleed off the worst of the air in the lines at the point where the brake lines go into the top of the ABS modulator ( I undid the easy to get to wiring plug going into the modulator, didn't undo the battery), then after bleeding at the modular, I bled each wheel in turn.

I decided that the bleeding tool / pipe from Super Creep Aue-toes was good enough for my purpose and I didn't need to vacuum bleed. This tool works best with the end kept under some brake fluid in a glass jar, so you can then keep a eye open on the air coming through.

a comparison between 'Daisy' a non-ABS model and 'Fred' ABS model, shows that the braking performance is back to how both vehicles were when they were first purchased. 'Daisy' has a firm pedal with excellent brakes and 'Fred' has that slightly vague feel as do all ABS models have and on a loose gravel surface pulls up well, with the ABS modulator jabbing back through the brake pedal.
.

[BathurstTom]

Hi Arthur, it has had two new master cylinders on it. I have my little box of trick which allows me to close/open each valve in the ABS module and when I close off the inlet valves (badly named as these are the valves that open/close the main lines from the ABS module to each wheel) the pedal comes up hard. Cycled the valves whilst holding the pedal down, operated the pump etc in the way described by wabco. No difference. opened pipes at the top of the ABS module and no air. I know there is air there somewhere, but just cannot get it out. Very, very frustrated and disappointed by this.

It has been to a "professional" workshop that originally rang me and recommended that I buy another car and put my drive train into it, then told me it was fixed, when it wasn't. That cost me $836. I keep thinking I must be missing something basic, but I cannot find it. All the pipes are in the right place and it has been manually bled, vacuum bled, pressure bled and reverse pressure bled to no avail. It can stay in the driveway. If I go near it at present, I would probably tqke an axe to it or something like that (swearing doesn't make it work - tried that - lots!).


Tom ,

[wrinklearthur]

(swearing doesn't make it work - tried that - lots!). It's ok my son you can tell me ----- It is after all, early Sunday!!! :Rolling::Rolling::Rolling:

It's time we ( The AULRO'ers ) formed a brains trust to drop around and have a look at this recalcitrant Disco of yours. Heck mate! I would come as well but I'm having enough trouble getting funds out of the Mummybank to go to town ( maybe I shouldn't be telling her that I'm going to Super Creep ), so to get up to your place might end up being a one way trip. :angel:

I have found that a Brains trust needs at least a number of two, as one only ends up talking to themselves and the replies don't make any sense at all. :D

Getting back to the master cylinder, two new cylinders did both the same have the same fault or did the air in the line cloud the situation?

I did find that I had a misalignment once on my Defender, when offering up the master cylinder to the booster and it's possible to get the parts together without seeing this. The sideways pressure was enough to still allow some action but I had some weird faults, so I went over my work and gave myself a proper kicking afterwards.

Be nice to have some new glasses to be able to see close up, as I have always been shortsighted and now to find I have short arms as well is a bit disconcerting! :eek:
.

[BathurstTom]

I will try one more thing, a combination of technical skill and basic "mechanicing". I will attach my box of tricks to the abs module and do one or two things. Both will involve opening the outlet valves. These are the valves in the abs module that stay closed during normal operation. When the ABS pump kicks open they open and the inlet valve closes, hence releasing pressure to the calipers. I will leave them open overnight to let any air rise to the top. I will then reverse pressure bleed from the wheels and try release the bulk of the auir by cracking open the pipes at the top of the abs module.

I am absolutely certain that the problem is in the ABS module. So one last try.


Tom.

[BathurstTom]

Hoo bl00dy ray!!! Brakes fixed!!! :p:):D

In the meantime I bought a 97 300tdi auto Discovery that hasn't missed a beat. That gave me the opportunity to look at the brake problem whilst I had the Disco in my driveway. One workshop that had a go at fixing it mentioned that they had to reverse the Proportioning valve as it was on backwards. They said it was fixed. Crap it was. Same problem. Manually bled the brakes until a nice firm pedal, but when started the pedal would sink to the floor. With this in mind, I used the old front brake lines to bypass the proportioning valve and voila! Problem identified.

Purchased new proportioning valve, manually bled the brakes and used my box of tricks to bleed the ABS module and then started it. Good firm pedal!!! Just tidfying up a few things on it for rego. Once it is registered, I will sell the 97 Disco.

Cheers,
Tom.

P.S. I actually fixed this on Christmas Day as a present to myself. A happy camper!

[wrinklearthur]

I'm pleased as well, as that problem led all of us on a merry chase.

A well deserved Christmas present for you.

.

[Boony73]

P.S. I actually fixed this on Christmas Day as a present to myself. A happy camper!

In celebration did you stand by the disco and fist pump or run around the yard screaming like a maniac.

[Debacle]

That's good to hear. I've been trying to get the brakes on mine right and it's come down the proportioning valve being the only thing it could be.

It's got rebuilt calipers, discs are good, new pads, new master cylinder, servo and braided lines and been bled multiple times. It's driveable and passed a rwc but you have to drive within the limitations of the stopping power it's got.

Got a new proportioning valve sitting there waiting to be fitted. Hopefully it will fix my problems as well.

[BathurstTom]

P.S. I actually fixed this on Christmas Day as a present to myself. A happy camper!

In celebration did you stand by the disco and fist pump or run around the yard screaming like a maniac.


I did fist pump once :D. The running around the yard screaming like a maniac already took place when I could not fix it ;). Interesting to note that this vehicle had had a major brake overhaul from a brake specialist in the Newcastle/Port Stephens area (without giving too much away). It was they who fitted the original proportioning valve on backwards and all the trouble stemmed from there.

Cheers,
Tom.