why do my brakes suck so bad?

[twastheglow]

I definately need some help here guys. And I apologize in advance for this being so long. I own a 1993 Nissan 240sx and a while back I installed Z32 calipers with steel braided brake lines to the front of my car. This was probably the beginning of last summer. Since the installation, I have had a brake pedal that literally 50% of the time felt firm and stopped the car high on the pedal and felt GREAT! The other 50% of the time the pedal would go almost to the floor and would start to slow the car. If I lift off of the pedal and pushed again it would firm up and work correctly again. Almost like it had to be pumped. Needless to say it wasn't the safest. After the installation obviously all the brakes were bled per FSM. After taking it for a drive and feeling how they were acting, I took the car back to the driveway and bled them again. That still didn't fix the problem. A couple weeks later after the new brakes set in a little, I re-bled them. Still no change. Then I broke down and actually took it ot a brake shop and had them bleed them too. That fixed the problem for about 10 minutes then they went back to being 50% of the time good, 50% bad. After talking to a number of people and asking around, it was recommended I buy a Z32 BMC and an ABS (double bubble) brake booster. (I do not have ABS) I thought maybe one of those 2 parts had gone bad. I finally got around to installing everything today. After the install, my friend and I bled the brakes for a good 30-45 minutes. After leaving his house the brakes were still quite spongy but were consistant so I didn't mind. As the night went on, the brakes firmed up and now were quite stiff and touchy (the way I wanted them). So I natually thought...problem solved. HOWEVER...now my f*cking e-brake light is on no matter how many times I've tried to apply it and disengage it to try to get it to release. Also, upon starting the car after it sat for about 2 hours, the brakes went back to being sh*tty all over again. After about 10 minutes of driving, they firmed up again. My questions are...

1) has anyone ever had a similar problem?
2) would it matter if I used an ABS booster on a car that does not have ABS?
3) why would this affect the parking brake and how can I fix it?
4) do you think I still have air in the lines making the pedal feel soft for a while?

Any help would be GREATLY appreciated. I'm quite frustrated at this point needless to say.
*mike*

[cdlong]

1. i haven't personally.
2. the ABS booster is just bigger and is only that way because the foundation brakes are a little bigger. it has nothing to do with the ABS system other than they are packaged together.
3. the parking brake is probably fine. the light comes on when you're low on fluid.
4. maybe. it sounds like there's a leak somewhere, possibly an internal leak in the MC.

you said the original problem is gone, the pedal just feels consistantly crappy now? if that's the case, there's probably just air trapped in the new MC. you should bench bleed it. i never did it when i installed my z32 MC but it might help.

if the original problem is still there, can you shed any light on the pattern of the crappy pedal? does it only do it when you haven't touched the pedal for a little while of driving? i've heard of similar problems that were the result of a warped rotor or bad hub.

[twastheglow]

1. i haven't personally.
2. the ABS booster is just bigger and is only that way because the foundation brakes are a little bigger. it has nothing to do with the ABS system other than they are packaged together.
3. the parking brake is probably fine. the light comes on when you're low on fluid.
4. maybe. it sounds like there's a leak somewhere, possibly an internal leak in the MC.

you said the original problem is gone, the pedal just feels consistantly crappy now? if that's the case, there's probably just air trapped in the new MC. you should bench bleed it. i never did it when i installed my z32 MC but it might help.

if the original problem is still there, can you shed any light on the pattern of the crappy pedal? does it only do it when you haven't touched the pedal for a little while of driving? i've heard of similar problems that were the result of a warped rotor or bad hub.

I checked the MC this morning and it's full. So I'm assuming there's no leak, AND there's no explanation for the e-brake light either. I did not bench bleed the BMC although I'm now thinking I should have. I'm going to be driving around all day running errands. I'll write a more in depth account of how the brakes act today. Maybe you guys can help me out. I also can't tell if the e-brake is really on or if it's just the light. If it is on, it's very, VERY soft.
*mike*

[DaPCWiz]

I haven't actually checked this personally cuz I never had to...

but I assume that if the master cylinder has a low fluid sensor, there is some harness you have to hook up to it so it can use it. If you didn't connect the harness when you put the new BMC in, that could trigger the light to stay on...

that might explain the light...

I would also go over the system again and check ALL point where the brake lines have a joint / connection / etc and make sure there is no evidence of brake fluid leaking. I would also check for rust on the brake lines under the car, make sure there's no hole that's leaking.

After all that if I don't find any leaks... I would try to bench bleed the bmc and see what happens...

[clark]

it sounds like air is getting into your lines. you should really thorouhly bleed them. also what is the condition of the rear calipers. before i rebuilt my rear brakes, they sucked air into the lines, thus the need to pump. the reason you need to pump is because air compresses much easier than brake fluid.

there is also an article on here to get rid of a spongy brake pedal, perhaps try that.

but yeah, bleed your brakes with someone to help, thoroughly, get two big ass bottles of synthetic brake fluid and completely drain the system.

[twastheglow]

I haven't actually checked this personally cuz I never had to...

but I assume that if the master cylinder has a low fluid sensor, there is some harness you have to hook up to it so it can use it. If you didn't connect the harness when you put the new BMC in, that could trigger the light to stay on...

that might explain the light...

I would also go over the system again and check ALL point where the brake lines have a joint / connection / etc and make sure there is no evidence of brake fluid leaking. I would also check for rust on the brake lines under the car, make sure there's no hole that's leaking.

After all that if I don't find any leaks... I would try to bench bleed the bmc and see what happens...


It's funny you say that about the harness...I was just outside checking it. It was plugged in. I unplugged it again and cleaned both the male and female ends and plugged it back in and no change. I still have that sweet light.

I have checked for fluid leaks. None anywhere. And that BMC is filled to the EXACT spot as when I left his house.

Sorry to sound ignorant, but how do you bench bleed the BMC? Under the circumstances, would that make a difference?
*mike*

[twastheglow]

it sounds like air is getting into your lines. you should really thorouhly bleed them. also what is the condition of the rear calipers. before i rebuilt my rear brakes, they sucked air into the lines, thus the need to pump. the reason you need to pump is because air compresses much easier than brake fluid.

there is also an article on here to get rid of a spongy brake pedal, perhaps try that.

but yeah, bleed your brakes with someone to help, thoroughly, get two big ass bottles of synthetic brake fluid and completely drain the system.

The rears seem like they're in great shape. My friend and I bled the hell out of them yesterday. Besides, before I changed the BMC and booster, I had bled them 3 times (and I mean REALLY well) and had them bled professionaly. Do you have a link to that article?
*mike*

[DaPCWiz]

Let me take a step back. Did you have *any* brake issues before you installed the 300zx setup? What clark said about the rear brakes could make sense... rear brakes on our cars have a tendency to fail, esp with high milage. I know I've had my share of issues with them.

Benching bleeding should be done when the bmc is first installed. Its a process for filling the BMC with fluid so that when you place it in the system there is minimal bleeding to be done. I'm not entirely sure if it will help you, but I've had many people tell me that it should be done.

couple links on the procedure... google "bench bleeding" and you'll see more. I've half ass bench bled a clutch master cylinder.... but never a bmc. I'd assume its not too different.

http://www.misterfixit.com/brakbld1.htm

http://www.tegger.com/hondafaq/mastercylinderreplace/benchbleeding.html


If none of the above helps you - let me speak from experience:

I installed a Q45 brake setup on my car... and I could never get it bled quite right. It wasn't inconsistent... but the pedal / pedal feel was never as good as I had hoped.

I ended up ordering speed bleeders for all four of my calipers and installing them. Ever since I bled with them, my brakes have been fantastic. I have talked to people about speed bleeders since there, and there are a number of people who claim they do not work as well as advertised. In my personal experience, however, they kick ass and I would recommend them to anyone. Bleeding is much quicker, and you can pump a ton more fluid thru the system faster w/o fear of getting air in the system. You can also bleed yourself, you don't need a buddy to help you.

[djcobra]

Just a thought, do you have your Z32 calipers installed upside down? meaning, the bleeding nipple is on the bottom end? I've seen people install the calipers incorrectly and have trouble with the bleeding; a very common mistake when installing these calipers. The bleeding nipple 'SHOULD' be on the 'TOP', thus allowing the air to rise and bleed much easier. This could be your problem if so then swap them around. I have a pair of Iron Z32 calipers installed along with my stock BMC with ABS (my ABS is disabled) works great.

Steve.

[UNISA JECS]

I checked the MC this morning and it's full. So I'm assuming there's no leak, AND there's no explanation for the e-brake light either. I did not bench bleed the BMC although I'm now thinking I should have. I'm going to be driving around all day running errands. I'll write a more in depth account of how the brakes act today. Maybe you guys can help me out. I also can't tell if the e-brake is really on or if it's just the light. If it is on, it's very, VERY soft.
*mike*

A full master cylinder doesn't necessarily mean no leak, it could be leaking internally past the most forward seal.

Check and make sure that the magnet is not stuck on the bottom of teh master cylinder which would make it give a brake light indicator.

Check and make sure your alternator is not dying, seems unrelated but in many nissan's teh brake light coming on and or flickering or dimming is a sign of a bad alternator.



Sorry to sound ignorant, but how do you bench bleed the BMC? Under the circumstances, would that make a difference?
*mike*

I can make a night and day difference, its mandatory to bench bleed teh master when ever it is replaced or a hardline at the master cylinder itself is removed or opened (mainly if teh fluid level emptied in teh master) just for good measure.

The rears seem like they're in great shape. My friend and I bled the hell out of them yesterday. Besides, before I changed the BMC and booster, I had bled them 3 times (and I mean REALLY well) and had them bled professionaly. Do you have a link to that article?
*mike*

Again you could bleed brakes for 10 days straight but if you did not bench bleed the master you would never bleed the air from the master.

[clark]

here's that article i was referring to before

http://www.zilvia.net/f/showthread.php?t=31732&highlight=spongy+brake+pedal

[ILoveMyRHS13]

It could be the master cylinder or one of your lines. My brand new master cylinder is already puking fluid everywhere out the back. :[
Best of luck with your brakes.

[racepar1]

The level sensor is either stuck or bad. Hit the resovoir of the master cylinder a couple of times with a screwdriver or something and see if the light will go off. If it doesn't then the level sensor inside the resovoir is bad or REALLY stuck. In that case your options are either just deal with the light and check the fluid level regularly or get a new master (or a resovoir if you can find one). As for the spongy pedal that sounds like there is air getting in the hydraulis system somehow. Did you bench bleed the master cyl before you installed it? If not then it is possible that there is an air bubble trapped in the master itself. Try bleeding the brakes starting with the master. To do this you bleed from the fittings the go into the master. Loosen one and have a buddy push the pedal down, then tighten the fitting and let the pedal up. Repeat for all 3 fittings untill you are satisfied that there is no air present and bleed the brakes from the wheels.

[twastheglow]

***UPDATE***
I tried driving the car today to run some errands. At first the pedal felt soft but still stopped the car fine. After about 10 minutes it tightened up and became firm again. Then my e-brake light went off by itself. Then within a minute of that happening, I could feel the rear brakesslowly being applied more and more until I had to really get on it just to keep the car moving. As soon as I let off the car would come to a stop. Now it's parked and I'm going to put the stock MBC back on it and try to rebleed everything again but much better this time. Since all the fluid obviously leaked out of the removed stock unit that I took out yesterday, can anyone explain to me step by step how to bench bleed the unit before putting it back in? Thanks again.
*mike*

[ILoveMyRHS13]

From what I remember with my master cylinder, it came with a kit. Get two clear plastic tubes that are big enough to fit over those holes on the side of the master cylinder, then put both tubes back into the thing for fluid and fill it with fluid, then get a screw driver and pump it into the opening on the front (or back, I forget) until there are no more bubbles.

[clark]

dude, the same thing happened to me on one of my other cars. i was a dumbass and was adjusting my pedal. you can twist the rod under you dashboard where your pedal connects to the actual brake booster.

you can loosen the nuts that connect your boster rod to the pedal, and you can twist the rod to back it off a little. what is happening is your booster is not adjusted properly and is always applying a little force. that is why your brakes have locked up.

it doesn't seem like a BMC issue, adjust your booster mang.

[twastheglow]

I think I get what you're saying. There's 3 fittings in the BMC. Do I do that to all 3?

Does any of these problems make any sense to anyone?
*mike*

[twastheglow]

dude, the same thing happened to me on one of my other cars. i was a dumbass and was adjusting my pedal. you can twist the rod under you dashboard where your pedal connects to the actual brake booster.

you can loosen the nuts that connect your boster rod to the pedal, and you can twist the rod to back it off a little. what is happening is your booster is not adjusted properly and is always applying a little force. that is why your brakes have locked up.

it doesn't seem like a BMC issue, adjust your booster mang.

Ok...but it's only the rears that are locking up. Do you think that's still the problem? We never measured the booster when putting it in. So if I adjust that nut where the fork is, that should fix the rears binding up like that?
*mike*

[twastheglow]

And why do you think it took that long for it to matter? I mean, it wasn't instant. It took a day.
*mike*

[S14Josh]

I'll put money on you having the calipers on backwards. A couple of my friends had the same problem with theirs, and we had no idea until we did a little reading lol. We bled the brakes probably 5 times with no luck then finally realized we had them on backwards.

Check your calipers right now, the bleeder valve should be on the top of the caliper, not on the bottom. if they are on the bottom of the caliper then this would be why your only feeling brake pressure some of the time, because air is trapped at the top of the caliper. When they are on upside-down you'll never be able to get all of the air out no matter how many times you bleed the brakes.

[twastheglow]

I'll put money on you having the calipers on backwards. A couple of my friends had the same problem with theirs, and we had no idea until we did a little reading lol. We bled the brakes probably 5 times with no luck then finally realized we had them on backwards.

Check your calipers right now, the bleeder valve should be on the top pointing up towards the car, not pointing towards the ground. if they are pointing at the ground then this would be why your only feeling brake pressure some of the time, because air is trapped at the top of the caliper. When they are on backwards you'll never be able to get all of the air out no matter how many times you bleed the brakes.

Thanks for the advice bro. I checked them back when I 1st started having issues last summer. Someone else had mentioned that to me so I did go outside and check them. I was a little nervous that that was what I did. lol But they were on the correct sides.
*mike*

[clark]

Ok...but it's only the rears that are locking up. Do you think that's still the problem? We never measured the booster when putting it in. So if I adjust that nut where the fork is, that should fix the rears binding up like that?
*mike*

mine took a couple back and forth drives from several errands. but it all happened in one day. one day i just decided to adjust my pedal beacuse i didn't like the feel. i didn't swap any new things on or do anything else to my brakes. adjusted the rod a shit load, and the pedal feel was awesome and i was like "oh shit, i fixed it". so that night i was driving and i was like uhh wtf, is my clutch slipping. no, it was my brakes squeezing the calipers. so i backed the rod off a little bit and everything was fine ever since. i really suggest you go under there and loosen the rod, count how many times you turn it just to have that on file.

[racepar1]

I have seen a bad brake booster cause the brakes to lock up a little at a time before. When you installed the booster did you screw with any of the adjustments? You can adjust not only the rod that goes to the pedal, but the rod that goes to the master cylinder itself. DO NOT screw with the rod that goes to the master unless you have a problem.

[twastheglow]

mine took a couple back and forth drives from several errands. but it all happened in one day. one day i just decided to adjust my pedal beacuse i didn't like the feel. i didn't swap any new things on or do anything else to my brakes. adjusted the rod a shit load, and the pedal feel was awesome and i was like "oh shit, i fixed it". so that night i was driving and i was like uhh wtf, is my clutch slipping. no, it was my brakes squeezing the calipers. so i backed the rod off a little bit and everything was fine ever since. i really suggest you go under there and loosen the rod, count how many times you turn it just to have that on file.

So it's that nut that the "fork" is attached to that you adjusted? The booster is off a different car so I wonder if it was in the same spot as the one I took out of the car. I'll go check that in a little bit. Thank you.
*mike*

[twastheglow]

I have seen a bad brake booster cause the brakes to lock up a little at a time before. When you installed the booster did you screw with any of the adjustments? You can adjust not only the rod that goes to the pedal, but the rod that goes to the master cylinder itself. DO NOT screw with the rod that goes to the master unless you have a problem.


I didn't adjust anything. Maybe I should have checked the pedal rod and checked to see if was in the same spot as the booster I took off the car. I'm going to go do that.
*mike*

[clark]

yeah the rod that conects to the fork. and the fork connects to the actual pedal using a "threadless bolt" and a cotter pin. just loosen up those bolts and then you can spin the rod with your fingers. if youc ant' spin with fingers just get some pliers in there.