Apologies as I know this has been covered, but I haven't seen this particular issue addressed.

With the Engine running, There's about two inches of throw before reaching Is a firm pedal. Pumping The pedal is accompanied by a whooshing sound of air. I can pump it repeatedly and it's still not firm.

However, With the engine off The pedal becomes firm with one or two pumps. Is that normal??

The stopping distance is terrible. It was never great but has gradually become worse. i first tried replacing the pads (which were worn to around 10mm) without improvement. One caliper had one piston which took a ton of force to compress, and should possibly be replaced. No idea when the fluid was last changed, but it doesn't look terrible. Original lines to calipers.

Where should I start to diagnose?

Thanks

 

sounds like the brake booster (?)

 

Thanks, and I appreciate the response.

However, I read elsewhere if you have a firm pedal when the engine is off and then you. Start the engine the pedal get sucked to the floor, this is NOT Is a brake booster issue.

any confirmation on this would be appreciated.

 

What model and year LR do you have? You should post this in the section of this forum for your particular vehicle.

 

Apologies, I thought had done this a while back.

2001 LR Discovery 2

Thanks

 

Master Cylinder with bad seals will cross bleed fluid F/R and can cause a mushy pedal, air in the lines can certainly cause a mushy pedal, and as far as pedal travel there is a rod in the Brake Booster which "can" be adjusted slightly to improve the slop in the pedal before it starts pushing on the M/C piston.

 

your booster is doing what it should do, provide the force via vacuum to help you send fluid out of the MC, and when you start the car it's functioning correctly. If the vacuum is not present, like booster diaphragm failure, or booster hose leak, or truck not running, then it would be much harder to push the pedal down.

plenty of reasons for 'mushy'...including ballooning brake rubber hoses. but i think you give a clue with the one caliper with hard to compress cylinder. This is not uncommon. neither is having the brake caliper pins rusted into place. especially if the truck sat a while. This can give the feeling of 'mushy' in that only one pad is really doing the work. You can't always tell piston travel when looking at the caliper even with someone stepping on the pedal for you. also, rust inside the brake lines can give uneven pressure to the calipers.

I don't think it's your MC or booster. Sounds like time for a major brake assessment. i would start with the calipers. take apart and grease all the sliding pins, check the pin boots. check the pads for uneven wear. with the caliper on the truck, and with hose attached, have someone GENTLY press on brake pedal a TINY bit and see if both pistons/caliper move. You may be able to see a difference. Do a complete fluid flush (about 2 large brake fluid bottles). I have some cheap generic dealer pads that came with my 04, but i checked all the calipers, and did a complete flush of brake fluid (and the rear lines took quite a bit of fluid before the new clear fluid showed. It was clear at first, then rusty colored, then clear again), and replaced the soft lines. it stops better than any Disco I ever drove.

 

Have you bled the brakes? The master cylinder leaks from the rear seal in to the booster, no other leaks are typical. The booster often does not fail digitally, all or nothing. They develop a small crack/leak and get worse. The booster is vacuum operated of course. Engine vacuum is highest at idle, lowest at WOT. So even with a crack in the booster it will often work in high vacuum conditions. You can get the highest vacuum be decelerating with foot off the gas down a long hill. On the other hand driving and suddenly lifting off and hitting the brakes gives the engine minimum time to generate vacuum, so the brakes will be minimal.

After you have bled the brakes my next guess would be the booster.

 

Also - I know it sounds dumb - but if you took off the calipers and re-installed them backward, the bleed screw will be at the bottom and you won't get all the air out, which would create the mushy pedal you're feeling.