Spongy Brake
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Spongy Brake
MOVING THIS THREAD FROM THE "GENERAL TECH HELP" PAGE TO THIS D2 PAGE
@Twillard
an 7, 2025 | 05:48 PM
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Twillard
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Spongy brake pedalNeed some help on brake work for my 2004 Disc 2.....seem to have a very spongy brake pedal.
I replaced, the master cylinder, pads, rotors, calipers and hoses. I manually bleed the brakes and commanded the abs bleed process with all new brake fluid. I still have a spongy feel and will not make a quick stop. I feel this is a safety issue, worst of all my wife drives the disc 2.
I will add I have not changed the brake booster, only because I can't find a new one anywhere.
What am I missing?
04D2CS
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I am having the same issue with my 04 D2, and am told it is the brake booster. sourcing the part seems to be difficult, did you figure out if that was the problem with yours?
@Twillard
an 7, 2025 | 05:48 PM
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Twillard
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Spongy brake pedalNeed some help on brake work for my 2004 Disc 2.....seem to have a very spongy brake pedal.
I replaced, the master cylinder, pads, rotors, calipers and hoses. I manually bleed the brakes and commanded the abs bleed process with all new brake fluid. I still have a spongy feel and will not make a quick stop. I feel this is a safety issue, worst of all my wife drives the disc 2.
I will add I have not changed the brake booster, only because I can't find a new one anywhere.
What am I missing?
04D2CS
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Joined: Feb 2025
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I am having the same issue with my 04 D2, and am told it is the brake booster. sourcing the part seems to be difficult, did you figure out if that was the problem with yours?
TReK
Joined: Sep 2020
Posts: 2,956
Likes: 754
From: British Columbia Canada
There is also a procedure to bleed the ABS circuit. There are threads here about that. You should try to find it, but from memory it’s something like selecting low range, turn on Hill Descent Control, then accelerate to a speed (I don’t remember the speed, but I think you accelerate to 20-30 mph) then take your foot completely off the accelerator pedal (don’t touch the brake pedal) and let HDC do its thing. Do this several times.
Banned
Joined: Aug 2021
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Maybe some of this info would help?
The best brake bleeding procedure is in post #13 on this forum post... https://www.aulro.com/afvb/discovery...es-solo-2.html
To be sure you've actually got the correct MC, Master Cylinder specs.... https://landroverforums.com/forum/di...rences-124145/
The best brake bleeding procedure is in post #13 on this forum post... https://www.aulro.com/afvb/discovery...es-solo-2.html
To be sure you've actually got the correct MC, Master Cylinder specs.... https://landroverforums.com/forum/di...rences-124145/
Recovery Vehicle
Joined: Jun 2014
Posts: 1,032
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From: Central NJ
Using a really long wire with alligator clips to the relay to pretty easy. That plus the normal bleeding should do it. I think I got my master cylinder from either FCP or Rock, either way it is an easy install.
Rock Crawling
Joined: Jul 2021
Posts: 482
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From: Top secret government location
Did you bench bleed the master cylinder before install? Not bench bleeding can lead to excessive bleeding needed to purge air from the system.
Did you power bleed or manually pump bleed? Sometimes power bleeding can cause cavitation resulting in never being able to get all the air out
Start with caliper with furthest from master cylinder first then working back to the closet? Are you using obd to bleed the abs or going into the fuse box?
Whenever possible I try to bleed with the nose sitting high, so gravity helps my cause. This is obviously much easier in vehicles that don't have abs. With aid of a small hand pump I can get the flow started and keep the reservoir full until I finally get all clear fluid out of the system. I find myself doing this work solo often, using the significant other as a helper is always terrific. If something goes wrong we immediately know who's to blame..
Its likely, if there's no leaks, you still have air in your system. A bad brake booster usually makes the pedal hard to press, not squishy. The vacuum assists your pedal pressure. When running you can also hear air swooshing from them sometimes if they are going bad, usually when pressing the brakes. A vacuum pump with gauge is a good way to test the diaphragm.
While you're under there look at y'all the brake lines. If they are original they could be breaking down and expanding rather than applying pressure to the caliper pistons. Its doesn't matter how your use your disco, these under built brakes could all benefit from stainless brake lines.
I've never needed to use hill decent mode to bleed brakes but some who have had squishy brake syndrome have used it to help their issue
I've never had to use this truck for brake systems but in ac systems if I can't find a slow leak I'll add compatible UV dye to it. This makes small leaks much easier to find.
Did you power bleed or manually pump bleed? Sometimes power bleeding can cause cavitation resulting in never being able to get all the air out
Start with caliper with furthest from master cylinder first then working back to the closet? Are you using obd to bleed the abs or going into the fuse box?
Whenever possible I try to bleed with the nose sitting high, so gravity helps my cause. This is obviously much easier in vehicles that don't have abs. With aid of a small hand pump I can get the flow started and keep the reservoir full until I finally get all clear fluid out of the system. I find myself doing this work solo often, using the significant other as a helper is always terrific. If something goes wrong we immediately know who's to blame..
Its likely, if there's no leaks, you still have air in your system. A bad brake booster usually makes the pedal hard to press, not squishy. The vacuum assists your pedal pressure. When running you can also hear air swooshing from them sometimes if they are going bad, usually when pressing the brakes. A vacuum pump with gauge is a good way to test the diaphragm.
While you're under there look at y'all the brake lines. If they are original they could be breaking down and expanding rather than applying pressure to the caliper pistons. Its doesn't matter how your use your disco, these under built brakes could all benefit from stainless brake lines.
I've never needed to use hill decent mode to bleed brakes but some who have had squishy brake syndrome have used it to help their issue
I've never had to use this truck for brake systems but in ac systems if I can't find a slow leak I'll add compatible UV dye to it. This makes small leaks much easier to find.
Last edited by PickleRick; Feb 19, 2025 at 09:49 AM.
Winching
Joined: Aug 2019
Posts: 602
Likes: 164
From: Charlotte, NC
I had a bad brake booster. Replaced it with a used one and it solved my issues.
My pedal was extremely spongy. Could almost reach the floor before brakes engaged. There was a noticeable noise of air being pushed.
My understanding is they are no longer sold new. If it is a brake booster you will have to find a used one and hopefully with not a bunch of miles on it.
I hope someone starts a rebuild for it. With the outer case being welded it may not happen.
FYI, after replacing the booster, lots of bleeding and re-setting the brake pedal switch is needed.
My pedal was extremely spongy. Could almost reach the floor before brakes engaged. There was a noticeable noise of air being pushed.
My understanding is they are no longer sold new. If it is a brake booster you will have to find a used one and hopefully with not a bunch of miles on it.
I hope someone starts a rebuild for it. With the outer case being welded it may not happen.
FYI, after replacing the booster, lots of bleeding and re-setting the brake pedal switch is needed.
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