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So I have had this issue for a while. I had it before I did the BBK. My brakes work just fine while driving, but when I come to a stop I am able to press the brake pedal almost to the floor? I just replaced the master cylinder in hopes that it was a master problem... but it still does it.
Anybody have the same issue and what was your fix? My technician thinks it might be a problem in the ABS, but I have no light or codes etc. And yes I am 100% sure I bled my brakes! I have bled them multiple times now with my technician.
I am going to try a set of SS brake lines in hopes it might be brake hose flex???
Thanks for any useful help!
02 6pd with 225K - 6th gen front calipers with stop tech slotted rotors, Hawk HPS, new master, stock rear calipers (not seized) with brembo blanks and hawk HPS. Stock brake lines.
My car does this too. It honestly might be normal because the brake booster is helping you. Once you turn the car off and try, after a few pumps the pedal should be very difficult to move. That is normal
wait you are ABLE to press it to the floor, or the pedal sinks to the floor? Even in a new system you can push it to the floor when the car is running. If you just mean it sinks to the floor or it gets easy to push to the floor, you might have a leaky seal in the MC
wait you are ABLE to press it to the floor, or the pedal sinks to the floor? Even in a new system you can push it to the floor when the car is running. If you just mean it sinks to the floor or it gets easy to push to the floor, you might have a leaky seal in the MC
This is the million dollar question.
Also, SS lines do not help much if at all. I have them on my Pathfinder and didn't notice much if a difference at all.
ABS shouldn't be the culprit, I'm assuming if the pedal does hit the floor, you have a leak somewhere.
I had a similar problem. On my 4th gen the brakes would work fine at driving speeds. When I would park, and use the brakes at slow speeds, the pedal would literally sink to the floor.
Turns out bad wheel hubs, and wheel bearings were to blame.
Drove around with the new master for a day now. Seems to be better too. It has also improved the brake feel a lot too.
Just wanted to make sure it wasn't just my car doing it.
Thanks for the input
so its better? Cant tell for sure based on that
Originally Posted by Max139617
I had a similar problem. On my 4th gen the brakes would work fine at driving speeds. When I would park, and use the brakes at slow speeds, the pedal would literally sink to the floor.
Turns out bad wheel hubs, and wheel bearings were to blame.
Im sorry but thats a load of garbage. wheel hubs and bearings have no impact on that. Whats more likely is that the brakes were bled and the bleeder valves properly tightened when the hubs and bearings were replaced, air and leaks in the lines are always more obvious at low speeds
Yeah it is better. Before it was a "soft" press to get it to almost the floor. Now it requires a "harder" press to get it to do it, but it still does it. I am ok with it now. If feels more normal. I am still going to get a set of ss brake lines to eliminate any brake hose flex.
i bought my car in feb. 2012 and i felt my brakes sucked. i replaced everything in may 2013 and i have the same exact problem as you are describing. i also did the 6th gen bbk but only because i was already having brake problems and figured this would be a fix/upgrade. i suggest you go reading through the thread i made and i still do not have a solution. my car stops but the pedal sinks low and my braking force is significantly weaker compared to my friends stock brakes. i feel his brakes are two thousand times better even though i spent like $800 on mine.
i have this idea it has something to do with my ABS unit aswell, i have no ABS lights and no abnormal ABS problems but i dont know what else it can be. good luck and please post back on any progress you've made.
I thought it was a known issue where the ABS unit/seals leak and allow the fluid to bleed back into the master cylinder? I understood it was something like that.
I thought it was a known issue where the ABS unit/seals leak and allow the fluid to bleed back into the master cylinder? I understood it was something like that.
never heard of this, searched around and nothing either.
So a little update - Its been a few days now and for whatever reason, its almost gone. The pedal is now "firm" at stop. I can still press it down probably half way, but nothing like before where is was "soft" and easy to press to almost the floor. I am not sure why it took a few days to get that way, but it did.
Changing the master cylinder also has given me back what I think should have been how the brake pedal should have felt before. The old one was original, so I can assume that over 10 years seals etc got weak.
So a little update - Its been a few days now and for whatever reason, its almost gone. The pedal is now "firm" at stop. I can still press it down probably half way, but nothing like before where is was "soft" and easy to press to almost the floor. I am not sure why it took a few days to get that way, but it did.
Changing the master cylinder also has given me back what I think should have been how the brake pedal should have felt before. The old one was original, so I can assume that over 10 years seals etc got weak.
I suggest you drive someone elses maxima of the same year who has known good brakes just to verify your brakes and pedal is where its supposed to be, because i felt my brakes were getting better after all the work but its just a placebo effect. Once i drove someone elses car i realized how big my problem was.
My Wife's 2000 Infiniti I30 always had great brakes for a non performance car but with 140k miles recently they randomly begin hitting the floor occasionally she said. Since it had no fluid leaks anywhere I see, its never had fluid loss so I installed a new Master cylinder a week ago & bled the system really good to rid any moisture in it.
After owning over 200 cars (Yep my **** is old) I learned long ago the master cylinder is generally the root cause here. But then it occurred again yesterday so I drove it till it done it again & yet again which took me awhile.
Finally I learned if her cars driven in city traffic where the pedal gets a good workout it seems to never happen.
We live 40 minutes outside the city so its 80 mph interstate driving a lot on it. If the pedal isnt pressed for 20-30 miles of highway driving your first pedal pump(s) it can hit the floor.
Anyone figure out what the random soft pedal problem is on these cars? Thanks
fwiw: I had power boosters fail on 2 older vehicles, one (1971 Nova SS) pedal was hard to press down like its engine was off. The other sucked the pedal straight to the floor "very fast" when you barely press it. At times I had to stick my toe up under it to pull it back up. This was my old 1969 Dodge Newport Fire Cheifs car with a 440 police interceptor so it did a huge smoke show at every stop. Darn car, always had everyone's head hanging out its windows..lol.
you would be surprised at how much of a difference a brake fluid flush can make on a car with old brake fluid.
my 2002 is at 353,XXX miles and the brakes feel great. no ABS issues, no locked up calipers, and no rubber lines have gone bad yet. flush the brake fluid once a year or whenever you change pads. I use a rubber line with a one way valve to make flushing by myself way easier.
My Wife's 2000 Infiniti I30 always had great brakes for a non performance car but with 140k miles recently they randomly begin hitting the floor occasionally she said. Since it had no fluid leaks anywhere I see, its never had fluid loss so I installed a new Master cylinder a week ago & bled the system really good to rid any moisture in it.
After owning over 200 cars (Yep my **** is old) I learned long ago the master cylinder is generally the root cause here. But then it occurred again yesterday so I drove it till it done it again & yet again which took me awhile.
Finally I learned if her cars driven in city traffic where the pedal gets a good workout it seems to never happen.
We live 40 minutes outside the city so its 80 mph interstate driving a lot on it. If the pedal isnt pressed for 20-30 miles of highway driving your first pedal pump(s) it can hit the floor.
Anyone figure out what the random soft pedal problem is on these cars? Thanks
fwiw: I had power boosters fail on 2 older vehicles, one (1971 Nova SS) pedal was hard to press down like its engine was off. The other sucked the pedal straight to the floor "very fast" when you barely press it. At times I had to stick my toe up under it to pull it back up. This was my old 1969 Dodge Newport Fire Cheifs car with a 440 police interceptor so it did a huge smoke show at every stop. Darn car, always had everyone's head hanging out its windows..lol.
You're describing exactly the phenomenon that I've been experiencing on my 4th gen ('96 i30) that started occasionally, but now all the time. For what it's worth, I've gone a long way down the troubleshooting path trying to fix this. The problem is EXACTLY as you describe. If you have a longer period of sustained driving with no braking, then if you start applying braking for, say, an upcoming red light, then you'll feel the brakes catch initially as they should, but as you apply more force to the pedal, not only does it sink further than it should, but you gradually have to apply more and more pressure to achieve normal stopping power. The feeling (at least for me) is that it's never going to stop, and I'm going to run out of pedal "throw" before I can achieve the stopping force that I need. Very distinctly different feeling from air in the system. If I quickly release the pedal (sometimes twice) and apply force again, then it will firm up nicely, and I can sit at the red light with what feels like perfectly normal braking pressure. I've tried coming to a stop on a slope with a single gradual push of the pedal, and I've literally HAD to pump it to get enough pressure to hold it from rolling backwards down the hill.
In any case, conventional wisdom is obviously the master cylinder. OK, fine. I replaced it; bench bled master; all four wheels bled in correct sequence; ABS actuated on wet road; re-bled; all fresh-clean fluid coming out at all four wheels. The problem felt a little better at first, but then came back. I did a post-mortem exam on the original master cylinder, and not only were the rubber seals 100% perfect, but the inside walls of the cylinder looked great as well. At this point, I'm starting to rule out the master cylinder. All of the other obvious checks have been made. All calipers and slide pins are perfect. Rotors are nice and straight (<0.002" runout) with good surface and healthy pads. Booster checks out perfect (no leaks, good check valve). Next thing to do was replace the soft lines. Replaced all 4 and re-bled, and although the new ones were indeed stiffer (less stretchy) than the originals, this made exactly zero difference.
What's left? The ABS module, unfortunately. I've studied the hydraulic schematic in the FSM and it certainly does look like there are opportunities for valves inside the ABS to leak and cause issues, particularly with regard to what's called the "reservoirs." From the diagram below, valves labeled "1" and "11" are normally open as you would hope. Valves labeled "2" (yellow rectangle) are NORMALLY CLOSED. If these normally closed valves are leaking when hydraulic pressure is applied during normal braking, or if check valves (9, 7, and 6) are leaking, then you can see that the reservoirs (3) can start to fill up. NOTICE the spring in each reservoir. So, in the same way that a leak to the outside world would cause the pedal to sink, a leak into these reservoirs under normal breaking could very likely "feel" like a leak and cause the slowly sinking pedal. Once the reservoirs are filled up and the pedal is quickly pumped, there's no more room for more fluid, so the pedal returns to normal height, and the system feels firm. Continue driving with no braking and the spring in the reservoir gradually empties it out again. I suspect that frequent braking doesn't allow the reservoir to empty as completely and so the pedal feels a little better. Of course, this wouldn't be an issue of the valves were staying closed.
I hadn't found ANYONE on the internet talking specifically about this until I recently came across an older YouTube video:
"The black rubber caps you see below the brake line connections are the LPA's (low pressure accumulators). This is where fluid goes during ABS event. Pull those caps off and put a straightened out paper clip in the hole and pump pedal. If they push out of the valve as the pedal sinks the ABS unit is the issue. Sometimes if you pump the pedal multiple times very quick you can get a good pedal because the LPA's will fill up and give good pedal. Spring pushes the piston/fluid back out in the system. Hope this helps!"
This video was in reference to a Ford Explorer, but the principle is the same for any ABS system. Looks like I get to figure out how to replace an ABS module!
(schematic below from 96 maxima FSM)
Last edited by pethelman; May 24, 2024 at 08:11 PM.
You're describing exactly the phenomenon that I've been experiencing on my 4th gen ('96 i30) that started occasionally, but now all the time. For what it's worth, I've gone a long way down the troubleshooting path trying to fix this. The problem is EXACTLY as you describe. If you have a longer period of sustained driving with no braking, then if you start applying braking for, say, an upcoming red light, then you'll feel the brakes catch initially as they should, but as you apply more force to the pedal, not only does it sink further than it should, but you gradually have to apply more and more pressure to achieve normal stopping power. The feeling (at least for me) is that it's never going to stop, and I'm going to run out of pedal "throw" before I can achieve the stopping force that I need. Very distinctly different feeling from air in the system. If I quickly release the pedal (sometimes twice) and apply force again, then it will firm up nicely, and I can sit at the red light with what feels like perfectly normal braking pressure. I've tried coming to a stop on a slope with a single gradual push of the pedal, and I've literally HAD to pump it to get enough pressure to hold it from rolling backwards down the hill.
In any case, conventional wisdom is obviously the master cylinder. OK, fine. I replaced it; bench bled master; all four wheels bled in correct sequence; ABS actuated on wet road; re-bled; all fresh-clean fluid coming out at all four wheels. The problem felt a little better at first, but then came back. I did a post-mortem exam on the original master cylinder, and not only were the rubber seals 100% perfect, but the inside walls of the cylinder looked great as well. At this point, I'm starting to rule out the master cylinder. All of the other obvious checks have been made. All calipers and slide pins are perfect. Rotors are nice and straight (<0.002" runout) with good surface and healthy pads. Booster checks out perfect (no leaks, good check valve). Next thing to do was replace the soft lines. Replaced all 4 and re-bled, and although the new ones were indeed stiffer (less stretchy) than the originals, this made exactly zero difference.
What's left? The ABS module, unfortunately. I've studied the hydraulic schematic in the FSM and it certainly does look like there are opportunities for valves inside the ABS to leak and cause issues, particularly with regard to what's called the "reservoirs." From the diagram below, valves labeled "1" and "11" are normally open as you would hope. Valves labeled "2" (yellow rectangle) are NORMALLY CLOSED. If these normally closed valves are leaking when hydraulic pressure is applied during normal braking, or if check valves (9, 7, and 6) are leaking, then you can see that the reservoirs (3) can start to fill up. NOTICE the spring in each reservoir. So, in the same way that a leak to the outside world would cause the pedal to sink, a leak into these reservoirs under normal breaking could very likely "feel" like a leak and cause the slowly sinking pedal. Once the reservoirs are filled up and the pedal is quickly pumped, there's no more room for more fluid, so the pedal returns to normal height, and the system feels firm. Continue driving with no braking and the spring in the reservoir gradually empties it out again. I suspect that frequent braking doesn't allow the reservoir to empty as completely and so the pedal feels a little better. Of course, this wouldn't be an issue of the valves were staying closed.
I hadn't found ANYONE on the internet talking specifically about this until I recently came across an older YouTube video: older YouTube video
and in particular, one of the comments:
"The black rubber caps you see below the brake line connections are the LPA's (low pressure accumulators). This is where fluid goes during ABS event. Pull those caps off and put a straightened out paper clip in the hole and pump pedal. If they push out of the valve as the pedal sinks the ABS unit is the issue. Sometimes if you pump the pedal multiple times very quick you can get a good pedal because the LPA's will fill up and give good pedal. Spring pushes the piston/fluid back out in the system. Hope this helps!"
This video was in reference to a Ford Explorer, but the principle is the same for any ABS system. Looks like I get to figure out how to replace an ABS module!
(schematic below from 96 maxima FSM)
Don't have braking/ABS issue on hand but this is a good to know. Very detailed finding! Thanks for the detailed sharing.
