ahardb0dy Posted July 12, 2012 Share Posted July 12, 2012 (edited) When I bought my 94 PF it needed a new master cylinder so I had my guy replace it, The truck stops fine but I noticed something and want to ask about it. If I'm sitting at a light with my foot on the brake pedal I notice the pedal feels like it will keep going down towards the floor and if I press on it harder it will go down further, but if I take my foot off the pedal and than step on the brake pedal again real quick it stops fine, it feels like the brakes are very grabby. What does this sound like if anything? Thanks Oh, my brake fluid is never low either, Edited July 12, 2012 by ahardb0dy 1 Link to comment Share on other sites More sharing options...
5523Pathfinder Posted July 12, 2012 Share Posted July 12, 2012 Sounds like there is air in the system yet, maybe it wasn't bench bled. Bleed all four corners and recheck it. Link to comment Share on other sites More sharing options...
ahardb0dy Posted July 12, 2012 Author Share Posted July 12, 2012 I know he bench bled it but could be some air, will have to try bleeding the brakes this weekend. Link to comment Share on other sites More sharing options...
Trogdor636 Posted July 12, 2012 Share Posted July 12, 2012 Weird. I just noticed my brake pedal doing this the other day! Link to comment Share on other sites More sharing options...
nunya Posted July 12, 2012 Share Posted July 12, 2012 A good proper bleed is in your near future, sounds like air to me. Link to comment Share on other sites More sharing options...
Alkorahil Posted July 12, 2012 Share Posted July 12, 2012 I agree, sounds like you need a good bleeding....... Link to comment Share on other sites More sharing options...
Precise1 Posted July 12, 2012 Share Posted July 12, 2012 BRING IN THE LEECHES!!! B Link to comment Share on other sites More sharing options...
tmoore4512 Posted July 12, 2012 Share Posted July 12, 2012 AIR!!! Mine did that when I first acquired it back in the day... an easy fix with someone in the drivers seat and a creeper... Or if you have access to a lift even better.... Link to comment Share on other sites More sharing options...
nunya Posted July 12, 2012 Share Posted July 12, 2012 AIR!!! Mine did that when I first acquired it back in the day... an easy fix with someone in the drivers seat and a creeper... Or if you have access to a lift even better.... sorry, I have plans this weekend Link to comment Share on other sites More sharing options...
snowboard419 Posted July 13, 2012 Share Posted July 13, 2012 Sounds like a bad seal in your new master cylinder. Air will just give a spongy feeling, but if your sitting with your foot on the pedal and it creeps towards the floor would indicate an internal leak in the master, hope it has a warranty. Link to comment Share on other sites More sharing options...
Alkorahil Posted July 13, 2012 Share Posted July 13, 2012 (edited) You may also wish to consider replacing the brake booster check valve. It is a small but important part that will lead to less effecient braking. I always recommend replacing it to customers when their vehicle is 12+ years old. I usually get very good feedback about how they noticed an improvement. WD21, D21 07/86-08/89 WITH Z21i PART NUMBER: 47478-01G02 WD21, D21, D21U 07/86-10/95 PART NUMBER: 47478-03B00 R50 10/95-07/96 PART NUMBER: 47478-03B00 R50 07/96-07/04 PART NUMBER: 47478-51E00 Edited July 13, 2012 by Alkorahil Link to comment Share on other sites More sharing options...
Tungsten Posted July 13, 2012 Share Posted July 13, 2012 I had some spongy braking with an aftermarket master cylinder even with the air bled out of the system. Switching to a Nissan master cylinder fixed that problem. I got it back again recently and I saw the fluid actually go down but it turns out that it was only air trapped in the system again. After filling the reservoir back up, it no longer appears to be going down except maybe a tiny bit with casual pad wear. Basically it's either air or a leak. Don't pump the pedal too much if it's spongy or you can end up doing more damage to the seals. Never depress the pedal all the way down during a bleeding procedure for that same reason. On an unrelated note, R50 pedals are always soft for no reason so you never know if the brakes are bad or not. Link to comment Share on other sites More sharing options...
Towncivilian Posted July 13, 2012 Share Posted July 13, 2012 (edited) Yes, R50 pedals are stupidly soft. Even though my brakes seem fine, I'll try replacing the check valve, mine's close to 11 years old so it may be time to swap it out. Thank for the suggestion Rob! Edited July 13, 2012 by Towncivilian Link to comment Share on other sites More sharing options...
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