Thread: Spongy brake pedal

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.

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.

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

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?
.

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.

New master cylinders are available

Ref;Land Rover Discovery Brake Master Cylinder FOR ABS | eBay

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




--------------------------------------------------------
Ref; Land Rover Discovery 1`94 ON Brake Master Cylinder With ABS | eBay

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.



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.
.

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...

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

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.

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 . 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.