# Spongy pedal after rear disc conversion?



## knock_it_off_hudson (Apr 30, 2004)

Since my brake drums were on the outs I decided to pony up for a disc conversion. I ended up getting NX2000 rear spindle assemblies, rebuilt NX2000 rear calipers, rebuilt NX2000 MC, new SE-R Ebrake cables, SS lines and some blank rotors. I already have AD22VFs on the front so I pretty much have full NX2000 brakes. But now, the pedal is VERY spongy. There is little pressure until I get near the bottom where the brakes will grab rather abruptly. It's kind of alarming to the point where I will not let anyone else drive my car for safety concerns. The Ebrake also feels "soft". I'm not getting confidence inspiring resistance when I pull the handle up. I can pull it all the way to the top without effort, whereas I remember not being able to do this before. The brakes DO work. The car stops without fade and the Ebrakes lock up the rear calipers. But the pedal just doesn't bite where one would expect it to. 

Anybody have any experience with this? I'm dead certain I got the NX2000 MC as I have a larger fluid reservoir than my stock one. Did I forget something in my parts list for the conversion? Does it have something to do with an ABS system not being present?


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## Oldnissanguy (Jan 6, 2005)

I know it's pretty basic, but are you sure you got all the air out of the brake lines? This is a classic symptom.


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## zacward (Aug 23, 2009)

Do you have enough brake fluid?


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## sunnysentra (Jul 24, 2002)

the bigger master cylinder would have the Yellow top on the resevoir. if its black, you have the smaller bore master cyl. The yellow top ones were the 94 altima and NX2000. black cap ones were the stock sentra with drums. 

You need to bench bleed the master cylinder also before hooking the lines up, or will get all kind of air into the system. try a proper reverse bleeder system that gets all the air out, not the typical push the pedal to pump the fluid out into the bottle. air rises and it wants to stay in the line going up even when you push the hell out of the pedal. 

Chris 92 classic


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## knock_it_off_hudson (Apr 30, 2004)

I rely on my mechanic for these kinds of jobs and he was certainly having me pump the pedal so I'll try bleeding them again. And I'll have to check that MC again, I think the top is black.


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## sunnysentra (Jul 24, 2002)

its the wrong one. Find a *95 altima non-abs master cyl or nx2000 *from a bone yard. They have taller resevoirs and the caps are yellow. the bore is larger also. I have to dig up photos, but I have one from when I redid mine. you need the bigger unit to push the fluid. my pedal went to the floor with the OEM master cyl from the drum setup.

Chris


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## knock_it_off_hudson (Apr 30, 2004)

sunnysentra said:


> its the wrong one. Find a *95 altima non-abs master cyl or nx2000 *from a bone yard. They have taller resevoirs and the caps are yellow. the bore is larger also. I have to dig up photos, but I have one from when I redid mine. you need the bigger unit to push the fluid. my pedal went to the floor with the OEM master cyl from the drum setup.
> 
> Chris


I sent a NX2000 MC core for a rebuilt unit but IDK, maybe they sent me the wrong MC. In any case, if I try a new MC it will be the Altima one. However I found two different part #s 46010-2B100 and 46010-2B101. Both are for the U13 and both are non ABS but I don't know what the difference is between the two. To be clear my pedal does not go to the floor, just close to it. I've had bad MCs before where the pedal just keeps going down until it hit the floor but in this case there's just lot's of pedal travel. It grabs really weakly and then suddenly strong near the bottom. I've had the lines bled at least three times so I think this is either the MC or the fact that I still have the OEM brake booster.


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## tlhingan (Jun 8, 2009)

It's not just the lines you need to bleed, buddy!
You need to properly bleed the MC also.
If there's any air in there, it will make the pedal spongy as well!
Like somebody else said, air bubbles up in the MC, so it will build-up at the top of the MC.


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## sunnysentra (Jul 24, 2002)

yes, if you have the right master cyl. then maybe the master cyl needs bled also. you need the air out of that also first. many bench bleed it first prior to install onto the booster. I did that myself first. I just wonder with your master cyl. check the part number on your unit and compare it to the correct part #. do you still have the rubber lines? that may also make it spongy a little. if its to the floor or most of the way, then maybe its the wrong one. 

Not sure on your part # on the altima. I will check courtesy. sometimes its just the mid-year model change # and not the actual master cyl that is different. You just have to make sure its non-abs. abs does not have the proportioning valves attached. they are the big bolt things that 2 of the lines connect into. 

Chris


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## pulsar86 (Aug 13, 2009)

The master cylinder and proportioning valves must be the correct ones to suit the rear disc brakes if not the brakes will be as you say, if you have that ok it will come down to bleeding.


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## knock_it_off_hudson (Apr 30, 2004)

sunnysentra said:


> yes, if you have the right master cyl. then maybe the master cyl needs bled also. you need the air out of that also first. many bench bleed it first prior to install onto the booster. I did that myself first. I just wonder with your master cyl. check the part number on your unit and compare it to the correct part #. do you still have the rubber lines? that may also make it spongy a little. if its to the floor or most of the way, then maybe its the wrong one.
> 
> Not sure on your part # on the altima. I will check courtesy. sometimes its just the mid-year model change # and not the actual master cyl that is different. You just have to make sure its non-abs. abs does not have the proportioning valves attached. they are the big bolt things that 2 of the lines connect into.
> 
> Chris


I checked the part # on the Fenco remanufactured MC I got and it's m52584 (NX2000)which is listed as 4-wheel ABS. I asked for the non-ABS unit and they sent the ABS one anyway:lame:


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## sunnysentra (Jul 24, 2002)

yeah, that is the reason. You have to have the NON-ABS model. that is why I used the 95 non-abs Altima unit, they were more available in the junk yards. I got one with 25,000 miles on it. like new. Check the junk yards. much cheaper. 

Chris


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## knock_it_off_hudson (Apr 30, 2004)

Just replaced the MC with a non-ABS U13 unit. The pedal feels better, more like how I remember a brake pedal should feel. It still feels like I have a touch too much pedal travel but the braking is solid now and more progressive instead of no resistance and then BAM.


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## sr20detb (Mar 29, 2010)

i see this post is a little idle but will the same 95 non abs mc work on a b14 also?? they all seem to bolt onto the booster the same on most models... will a 300z mc bolt on too? i have a 95 b14 with 300z calipers and no pedal feel.. thanks


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