# I'm gonna brake sumpthin....



## blakshukvw (Dec 26, 2005)

To begin, I am an experienced mechanic and have prided myself on brake work in the past and not being stumped by more complicated systems such as ABS. So I've been working on a 97 GXE, non ABS, for the last two days trying to determine why it won't maintain brake pressure. The car has two new rear wheel cylinders, drum brake shoes and hardware, new front rotors and ceramic pads, a new right front caliper, and a new master cylinder all in the last 2 days. I bleed the system and remove all air but the pedal is still mushy and when pushed long enough, eventually goes to the floor.
I've had it better at times, enough that I tried to drive it only to have the brakes fade over the cousre of about 2 miles to the point that it's unsafe to drive. Even when I felt I had gotten somewhere with the pedal feel and driven it, it will never lock up the front brakes. No matter how hard I push, they will not lock up and the pedal goes to the floor. After a few attempts at this, the brakes are so hot they basically quit working at speeds over 35 as well as smell from being really hot.
If I go back and check for air, there is air present again in the system, albeit not much. Now I know that means leaks, but there are no fluid leaks to be seen. I replaced the master because I thought the seals were bad causing air to be pulled past them and into the system. No such luck.
I am pretty unfamiliar with ceramic pads. Maybe someone with some more experience with them can chime in. I would guess that they just don't have the bite that metallics or semi-metallics do, however, they can't be this bad. They would simply be unmarketable due to being unsafe. Do the ceramics fade faster than metallics?
So obviously I have what seems to be two problems. One, I have continuous air in the system causing a spongy pedal and no brake power in the front of the car. I believe if I could solve the problem with the spongy pedal it would fix the other.
All of this began after a local Meineke wrote an estimate for repairs on the front brakes and the outside brake pad mysteriously went missing. Thus causing damage to the rotor and runing the caliper due to the piston coming out and leaking all of the fluid out of the system. The caliper I installed on the right front is unfortunately a reman unit from Oreillys. I usually try to avoid reman parts. All of the other parts I mentioned above are new items.
So with that long post, I conclude. Any help would be appreciated and any scenarios will be entertained. Let me know what ya got. Thanks.


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## rogoman (Dec 16, 2004)

blakshukvw said:


> No matter how hard I push, they will not lock up and the pedal goes to the floor. After a few attempts at this, the brakes are so hot they basically quit working at speeds over 35 as well as smell from being really hot.
> If I go back and check for air, there is air present again in the system, albeit not much. Now I know that means leaks, but there are no fluid leaks to be seen. I replaced the master because I thought the seals were bad causing air to be pulled past them and into the system. No such luck.


I'm a little confused about the front brakes getting extremely hot. You say the front brakes will not lock up so why do they get so hot. Have you checked the front caliper slider pins for proper lubrication; if not, the pads may be locking up against the rotors.

As far as air in the system, remove the master cylinder from the car and bench bleed it. What bleeding procedure do you use? Do you have someone help you pump the brake pedal and holding it down while you crack open a bleeder port?


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## slavrenz (Apr 16, 2010)

How many times have you bled it? Often, it takes a lot more than you think it would. The only other thing I can think of is that your brake booster is leaking.


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## blakshukvw (Dec 26, 2005)

rogoman said:


> I'm a little confused about the front brakes getting extremely hot. You say the front brakes will not lock up so why do they get so hot. Have you checked the front caliper slider pins for proper lubrication; if not, the pads may be locking up against the rotors.
> 
> As far as air in the system, remove the master cylinder from the car and bench bleed it. What bleeding procedure do you use? Do you have someone help you pump the brake pedal and holding it down while you crack open a bleeder port?


The slider pins were greased when I installed the pads and still work fine. I can see the calipers move when the pedal is pushed and then retract when the pedal is released. I too wonder how they could be getting so hot.

As for the bleeding, I didn't bench bleed the master but after installing it, with the help of another, I bled it in the same manner you would a caliper. I cracked the lines open at the master and had someone push the pedal and then closed the line before lifting the pedal. I got air out until a steady stream of fluid came out. In my experiences, I have never had to bench bleed a master. I really don't think that could be the problem because it did the same thing with the old master too. Do you think that could really be the problem? I am not so convinced. In my experience, any air in the master would be pushed out when conducting a bleeding at the calipers. Like I said, I even bled it at the lines going into the master.

Don't know how I'm going to bench bleed it. It only came with two of those little adapters you stick in the ports and rubber hoses to bleed back into the resivior. I would need 2 more of the adapters and hoses.


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## blakshukvw (Dec 26, 2005)

slavrenz said:


> How many times have you bled it? Often, it takes a lot more than you think it would. The only other thing I can think of is that your brake booster is leaking.


I've bled it countless times over the last two days. In the past 2 days, I've run two large Orelly bottles of fluid through the system. I can get all of the air out. Then after a test drive and the brakes pretty much fail I keep revisisting the bleeders just to see if there's more air in the system. Pretty consistently I see more air somewhere. So there's air being drawn in from somewhere or maybe it's boiling the fluid?? I choose to believe the first one, although both could be happening.

I thought that maybe the brake booster was leaking too. I check the one way check valve that holds the vacuum in the booster and it works fine. One thing I thought was funny, I held the pedal firmly and jazzed the throttle and the brake pedal dropped a little when engine vacuum went down. Assuming the check valve works, which it does because I checked it, why would this happen? If the booster was leaking externally, wouldn't the result just be a harder to push pedal? Simply like an unboosted car?

I'm beginning to wonder about the reman caliper I installed. I never like to use this garbage from local parts monkeys. So many times I've seen "reman" parts just be cleaned and painted and then resold with no new parts installed. I did look closely at the caliper and it does have a new dust seal at least but that tells me nothing about the inner seal or bore. Of course it's not leaking fluid externally so maybe it's okay. I don't know.

This is why I say I'm so confused by this situation. I'm pretty frustrated with what should have been a couple hour job, at the most.


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## rogoman (Dec 16, 2004)

blakshukvw said:


> As for the bleeding, I didn't bench bleed the master but after installing it, with the help of another, I bled it in the same manner you would a caliper. I cracked the lines open at the master and had someone push the pedal and then closed the line before lifting the pedal. I got air out until a steady stream of fluid came out. In my experiences, I have never had to bench bleed a master.


In my past experiences with brake systems, there were some situations where I had to bench bleed the master cylinder; ran into a soft pedal problem; the replacement master cylinder had air in it that just wouldn't purge with normal air bleeding. I've also ran into a bad replacement master cylinder that continued to give a soft pedal no matter how many times I bled the system. Hope this helps.


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## blakshukvw (Dec 26, 2005)

rogoman said:


> In my past experiences with brake systems, there were some situations where I had to bench bleed the master cylinder; ran into a soft pedal problem; the replacement master cylinder had air in it that just wouldn't purge with normal air bleeding. I've also ran into a bad replacement master cylinder that continued to give a soft pedal no matter how many times I bled the system. Hope this helps.


Okay. I can see that there are circumstances that may be different than others I've had. I guess it's worth a try. How did you bleed them in the past? To bleed it on the bench it would require 4 of those little plastic fittings in order to do it properly. The unit Ihave only came with two like I mentioned. It wouldn't work if I only used the two I have and bled two of the ports at a time. Air would be sucked into the other two while trying to do this. I guess I have to acquire two more and more hose.


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## leapfrog (Jan 26, 2010)

Pull that re-man off and check! However wld also look @ m/cyl How are the rubber flexi pipes? Do you get air at all bleed points?


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## sup_mario (Jun 30, 2010)

Thanks for sharing your story. Hope this thread can help you.


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## blakshukvw (Dec 26, 2005)

leapfrog said:


> Pull that re-man off and check! However wld also look @ m/cyl How are the rubber flexi pipes? Do you get air at all bleed points?


I assume you're saying remove the caliper and check it. Check for what? 

The rubber hoses on the car look awesome for a car with 180k miles. No splits in the outer rubber skin at all.

I usually get some air out of which ever bleeder I open first.


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## blakshukvw (Dec 26, 2005)

sup_mario said:


> Thanks for sharing your story. Hope this thread can help you.


Are you trying to share something with us?


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## blakshukvw (Dec 26, 2005)

YOu know I forgot to mention that I did bleed the system with a powerbleeded and still had this problem. If there wa sany air in the master, that in my opinion would have removed it.


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## tompumped (Jan 31, 2010)

If nothing works out for you i'd try the phoenix injector it has helped me out in the past. There was only one car that I had a hell of a time getting all the air out of the system and that solved my problem. 
You can do reverse fluid injection with the tool which solved my problem. It can also be used to vacuum bleed and pressure bleed.


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## blakshukvw (Dec 26, 2005)

I'll check it out. Thanks for the advice.


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## STEALTHY SENTRA (Sep 1, 2009)

do u have a nissan service manual? check for location of proportioning valve for leaks.


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## blakshukvw (Dec 26, 2005)

STEALTHY SENTRA said:


> do u have a nissan service manual? check for location of proportioning valve for leaks.


No leaks at the prop valve. I worked on it again today. Bled the brakes again, got some more air out. Drove it and it seemed better. Bled it again got the last bit of air out and it brakes better. Still not to my personal liking but I think it's the best it gets with an economy car and some old components syill in the system.

I used ceramic pads and I also think they contribute to my feeling like the brakes just don't have much power. I don't like them and would never use them on my car.


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## LvR. (May 26, 2010)

So you replaced the RF caliper ................ did you actually get a caliper to go on the right of the car? ................. iow is the bleeder nipple located towards the top of the caliper rather than towards the bottom?

A LH caliper will physically fit and work, but because the bleeder nipple is on the under side of the caliper's hydraulic cavity, air will inevitably get trapped in the top of the cavity, and you will never fully purge the system of air no matter what you do.


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## blakshukvw (Dec 26, 2005)

Yeah it's the correct fitment. It's the only part I installed that was reman though. It didn't leak but I wonder if it isn't some of the cause for the problems. Of course with the brake lines actually going up and over the height of the resivior, it's completely possible to get some air in the system trapped up there and take a while to remove.


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## LvR. (May 26, 2010)

Well - since you seem to have an answer for every suggestion and seem to have checked the obvious, there is one thing left to do:

When you bleed the system to the best of your abilities, make sure you take careful note of the exact level of the master cylinder reservoir *with the brake pedal depressed fully and as hard as possible*. Drive around a bit and actually cause the brakes to go dangerous as you described earlier ................ does the master cylinder level stay exactly the *same as before with the pedal depressed*? 

If yes, you have air in the system and you will have to improve your bleeding strategy to get rid of it - if no (iow the level dropped) you are loosing fluid somewhere and if you cannot see it come out of the vehicle anywhere the only hidden place left to look for it is in the booster (leaking rear seal/piston assembly causing the whole booster diaphragm to get swamped with fluid)

The filling of the booster with brake fluid is a common problem on 1st generation VW Golfs but I have not seen it on a Sentra yet


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## blakshukvw (Dec 26, 2005)

I've seen that on golfs too. The brakes are better than they were, but like I said, I still think there may be air in the lines cause the pedal isn't very firm. Of course they don't fade anymore so that would indicate that there wasn't air in the system. I can exactly put my finger on it but they're just not right. Most cars you push the pedal down and it gets to a point where it gets firm and stops. This one never feels that confidence inspiring. Then again, I'm used to my sentra's brakes with Hawk pads, stainless lines and super blue fluid. It's been driven now for 3-4 days and no problems so maybe it's just as good as it's going to get.


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## LvR. (May 26, 2010)

Guess as long as you are the only driver its not a problem as such.

FWIW - I consider the Sentra's standard non ABS brake setup (perhaps only mine?) to be the standard to work to-wards and strive for ................ I would really be miffed if it was to change its behavior and feel that's for sure.


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