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Mushy Brakes - mystery???
- Thread starter CL65 Captain
- Start date
Yes, it is integrated into the master cylinder. They used to be a separate component, but that was in the 1960's.
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From what I gather: the brake system is solid when the car has not moved. If so that should eliminate the brake lines, master and all that.
Is it the same when then engine is running but when the car is still has not moved?
What happens if you put the car on stands and spin the wheels?
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I'm still betting on something that is messing up the geometry between the rotor and the caliper. I would check to see if a rotor is mounted unevenly, or a wheel bearing is not great or something like that.
Drew
No this doesn't matter whether the car is moving or standing still. In the garage with the car up on jacks, car off - brakes are firm. Start car, brakes drop a little bit (normal~ pb is working). Press on brake pedal - no real pressure until almost the end of the stroke. Holds pressure, pumping doesn't improve it.
No noticeable play in any of the wheel bearings (I track the car often and check this all the time).
Calipers, rotors and caliper bracket have been off - checked and reinstalled.
Like I said, I'm betting it's the lines. Here's why:
1. new master cylinder
2. bled very, very well
3. With car off it's OK ~ not enough pressure to balloon the lines. With the Power Booster (car on) they maybe ballooning.
4. I'm sure that as many times as I have changed pads ~ 20+ times a year that I have stretched the lines as they have on occasion fallen and dangled by the lines.
But there are no leaks.I should have the lines on by early next week, and I will report back.
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No this doesn't matter whether the car is moving or standing still. In the garage with the car up on jacks, car off - brakes are firm. Start car, brakes drop a little bit (normal~ pb is working). Press on brake pedal - no real pressure until almost the end of the stroke. Holds pressure, pumping doesn't improve it.
No noticeable play in any of the wheel bearings (I track the car often and check this all the time).
Calipers, rotors and caliper bracket have been off - checked and reinstalled.
Like I said, I'm betting it's the lines. Here's why:
1. new master cylinder
2. bled very, very well
3. With car off it's OK ~ not enough pressure to balloon the lines. With the Power Booster (car on) they maybe ballooning.
4. I'm sure that as many times as I have changed pads ~ 20+ times a year that I have stretched the lines as they have on occasion fallen and dangled by the lines.
I should have the lines on by early next week, and I will report back.[/QUOTE
i dont buy it !!! however i was not there when you changed the pads
#1 when did problem start
#2 at what point did you change the M/C cyl.
# 3 do you have a infra red thermo gun (most valuable tool in any techs box )use it to check everthing from engine misfire ,wheel align, A/C ,brake rotor& pad temp,tire pressure ,even the bio reaction in your septic tank
#4 pm me for my ph# we'llput our heads together , i love these problems
#1 - the problem has been slowly progressive. However, last week at the track I went through the rear pads to the backing and had to change them out in the parking lot with my "get me home" pads. It was real mushy after that - I am sure that I let air in when changing the rear pads and didn't bleed them ~ I was in a gas station parking lot with a 180m highway drive home. The next day, took off all four pads (Carbotech track) and rotors to inspect and install my street pads (OEM). Reinstalled caliper brackets, rotors, pads and calipers. Bled the lines. Quick drive - bled the lines some more.
Something that I thought was a little strange is the last three sets of pads I have - the rears wore faster than the fronts. I go through pads in a couple of track days.
#2 - I inspect the car head to toe after every track weekend. I noticed that there was a little bit of spray or wet area on the face of the brake power booster between the PB and the master. Only happened on the track where I am very hard on the brakes. So I changed it out with a new OEM master, figuring that it was the culprit of the mushy brakes. Bench bled the master. Bled the brakes, bled the brake some more, bled the brakes all after noon.
#3 - Yes I have a IR temp tool and a tire pyrometer. Not sure how this would play into the brake senario?
#4 - Will post back after I install the new brake lines.
1. Did you bench bleed the new master?
2. Did you check the "depth" spec on the master per the service manual?
Regards,
LarryB
2. Did you check the "depth" spec on the master per the service manual?
Regards,
LarryB
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- 15 May 2004
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As you say it has been slowly to progressive? Where did the progressive phase start? With changing the master? I guess you've used a new one, right? You said you flushed the hole night. For my car this was not enough after a new master. It was more like flushing - using the brakes/driving - flushing - driving - and so on. About 3-4 cycles.
I think Larry is pointing in the right direction. I'd have a look at the brake pedal mechanism and the play. Feel the play of the brake pedal with your hand. You should feel the resistance when the booster stick is touching the master.
I think Larry is pointing in the right direction. I'd have a look at the brake pedal mechanism and the play. Feel the play of the brake pedal with your hand. You should feel the resistance when the booster stick is touching the master.
thats exactly where i was going, compensating port, seen it many times
Changed the lines with new SOS lines. No change.
While I was changing the lines, I bled directly from the hard lines to make sure there was no air in the lines or master cyl. Then after installing the lines I bled from the caliper. Finally, after everything was back together I went around and bled a final time RR, LF, LR, RF.
No change. It still feels mushy and you have to brake hard to get it to stop (end of the travel) ~ similar to brake fade.
I pulled all the calipers and there are no leaks showing on the bleeder screws, brake lines or around the piston dust seals.
What next? Caliper rebuilds? All the dust boots look like they are in good condition, soft rubber and no cracking or tears. Car has 38,000 miles, but quite a few track days with track pads (ie very high heat).
While I was changing the lines, I bled directly from the hard lines to make sure there was no air in the lines or master cyl. Then after installing the lines I bled from the caliper. Finally, after everything was back together I went around and bled a final time RR, LF, LR, RF.
No change. It still feels mushy and you have to brake hard to get it to stop (end of the travel) ~ similar to brake fade.
I pulled all the calipers and there are no leaks showing on the bleeder screws, brake lines or around the piston dust seals.
What next? Caliper rebuilds? All the dust boots look like they are in good condition, soft rubber and no cracking or tears. Car has 38,000 miles, but quite a few track days with track pads (ie very high heat).
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Originally Posted by C-speed said:
^^^ Did you do this?
I don't have a helper. However, I retracted the pistons on each caliper as if changing the pads, reinstalled and pump the brakes and each caliper tighented up like normal. I did each one at a time so I could check each one.
sorry to hear you are still struggling-
calipers are a simple device, there is not much that can go wrong there so as long as they are not stuck or leaking do not waste your energy on them.
seems that the nature of the problem is tied to a brake fluid volume change so any components that can permit that are suspect. since you changed the lines, my gut feeling still points toward master cylinder or maybe the abs unit. i do not know how exactly abs unit functions on nsx but it is a pressure control device just like the mbc- maybe some valves are stuck? if it was my car, i would simply get a new o-ring kit for the mbc and (i know it was new) rebuild it. you never know, maybe there was a crack or slit in a seal or the part sat on the shelf for a while? it does not take much of a damage to leak pressure.
I don't think its the MBC - the old one and the new one give the exact same results.
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It f*cks, sorry looks like this:
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Never seen one.
- Joined
- 15 May 2004
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You don't have brake test stations in the US?! If you use one you may be able to locate to problem if it's related to only one wheel.
I wonder if your problem is related at all to the ABS(I believe 00+ ABS is inline with the rest of the brake system right?). Maybe pull the ABS fuse to see if it works differently? Just a thought 
What about the brake booster?
Give us a timeline when this problem happened. Did you track your car the previous day? Did u swap the pads for street pads at the track and drive home? Was it fine on the drive home and then this problem just appeared overnight?
Give us a timeline when this problem happened. Did you track your car the previous day? Did u swap the pads for street pads at the track and drive home? Was it fine on the drive home and then this problem just appeared overnight?
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ABS in the 2000 is inline with the brake system and doesn't have a separate system (reservoir) like the earlier years.
The brake booster seems to be working like normal. When you start the car the pedal drops a 1/2" like normal. The brakes aren't hard to push ~ they are acting like there is air in the system ~ however, there doesn't seem to be a leak and they have been bled to death.
The brake booster seems to be working like normal. When you start the car the pedal drops a 1/2" like normal. The brakes aren't hard to push ~ they are acting like there is air in the system ~ however, there doesn't seem to be a leak and they have been bled to death.
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maybe you can have someone else, a friend, look at it- i am not saying you are incapable but from experience i've noticed that one may overlook or miss details when stuck in a loop. from what you described you pretty much replaced everything but the booster itself (which may be faulty).
yep. I'm taking it up to Brian's (SourceNSX) Shop next week. I have tried everything I can think of and then some. Swapped out the front rotors and pads with some old ones I had and added the speedbleeders back in tonight. Getting read to go for a test drive, but I am not holding my breath. :frown: Time to put it on the rack and have someone else give it a shot.
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- Joined
- 27 June 2003
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What parts are needed to replace the master brake cylinder?
http://www.acuraoemparts.com/delray...=BRAKE+MASTER+CYLINDER&ListAll=All&vinsrch=no
I'm hoping its not #1 and #5 together... thats almost $900 just for parts!
My brakes are a little mushy and it just started happening today... I checked the fluid and its a little low. I hope its not leaking somewhere! I have SS lines from Dali, with carbotech pads if I remember correctly... with the ATE Super Blue Brake fluid... why would there be less fluid in the reservoir?
http://www.acuraoemparts.com/delray...=BRAKE+MASTER+CYLINDER&ListAll=All&vinsrch=no
I'm hoping its not #1 and #5 together... thats almost $900 just for parts!
My brakes are a little mushy and it just started happening today... I checked the fluid and its a little low. I hope its not leaking somewhere! I have SS lines from Dali, with carbotech pads if I remember correctly... with the ATE Super Blue Brake fluid... why would there be less fluid in the reservoir?
