Any brake experts want to give this a "crack"?

[twastheglow]

I definately need some help here guys. And I apologize in advance for this being so long. I own a '93 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*

[NismoRacer34]

did you change the master cylinder to z32's?i don't know why it would be firm once in a while though. the smaller master would require more than one pump to engage the larger brakes.

[hilux30]

1.how did you bleed the brakes? all four corners I hope with friend in car pumping and holding right?

2. Did you push the pistons for the callipers in with the bleeder closed, hooked to the brake lines?

3. did you do a line lock test: Close all lines (with line locks) at the rubber hoses at all four corners, and then pump pedal, if it's still doing it then master is bypassing and bad.

[twastheglow]

1.how did you bleed the brakes? all four corners I hope with friend in car pumping and holding right?

2. Did you push the pistons for the callipers in with the bleeder closed, hooked to the brake lines?

3. did you do a line lock test: Close all lines (with line locks) at the rubber hoses at all four corners, and then pump pedal, if it's still doing it then master is bypassing and bad.

1) Yeah, we did all four corners, pumping and holding.2) I didn't do anything with the caliper pistons. I'm actually not even sure what you mean.3) No, I didn't do a line lock test.

I really didn't know I had a problem until I had left his house for the day. Like I said, they seemed consistant for the 1st time so I thought I was all good. THEN they firmed up and felt great! Then I thought I was even MORE all set. lol Then I got the e-brake light, then my pedal feel went back to so-so. This morning I checked the MC to make sure it wasn't low. I've been told that would cause an e-brake light. The MC was full. So no leaks and no explanation for the light.*mike*

[Rucca]

Well, the brake booster helps you apply extra force to the brakes, so it really isn't an ABS related part. On rockauto.com I cannot find anything but a Brake Booster for a Z32, no ABS or non-ABS part so that would lead me to believe they are the same.

A faulty brake booster would leave you with a hard pedal that felt ineffective. Like stepping on a rock, and you describe the pedal as spongy so lets rule brake booster out.

Master cylinder problems would leave you with a spongy ineffective pedal, however, you have replaced the MC so I assume that is OK. Although, I would keep the MC in mind. New parts can be bad, and if it is a used unit you never know.

Since you say that bleeding the brakes professionally left you with firm brakes for 10 mins, I'd suspect a problem with the calipers possibly having a small leak and letting in air but not letting out fluid or not much fluid at least.

In short, I'd check all lines for leaks. If you don't find any put your old 240 calipers back on and see if the problem goes away. If it doesn't, replace MC, if it does, replace Z32 calipers.

[Vegascorbin]

Did you bleed the Master Cylinder?

Bleed it the same as you would a wheel cylinder but do it before any wheel cylinder.

Also are there any brake lines that could be getting overheated from the exaust? That could also cause strange problems.

[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*

[Rucca]

Basically put the MC in a vice with a cloth wrapped around it. Hold our fingers over the holes the brake lines need the attach to and use a screwdriver or something the press in the master cylinder. Do this a few times and hold your fingers tight so that it can force some fluid and air out but when it sucks back in it just gets your fingers and doesn't let air in.

[nismotuner1]

hey, it's nice to see someone else in binghamton has love for the s13!! the rear brakes started to lock up? that sound pretty weird are your rear calipers leaking or seized up? caliper pins lubed and free to move? not shure if this will fix it but just a thought.

[Hijacker]

So far, all signs would point me to a faulty MC. Since you didn't understand bench bleeding, I'm going to assume you have air in the master cylinder. If you get air in the MC, you will have inconsistent pedal feel, and the air will never travel to the calipers, so you'll bleed them and think all the air is out.

Before you go swapping the MC back to the stock 240 unit, do this:

Have a friend pump and hold for you. Also have a cloth to catch brake fluid

Start with the rear line.-Break the line loose-Have your friend pump once and hold-Let the fluid squirt out. If there's air, you'll get some gurgling and spitting-Tighten the line-Let your friend take his foot off the pedal

Repeat that procedure until you don't get foamy sputtering. Then move up the master cylinder to the middle line and repeat the procedure, finishing it off with the forward line.

^That's a basic bench bleed with the MC mounted in the car

After you do this, go back and rebleed the calipers again to assure you that there is no air in the lines.

[smokerider]

also try checking the piston behind the clutch master cylinder it might be defective. or see if u can up grade. i remember when i had this problemthe fluid leak around my clutch pedal. hope this helps.holla back.

[RareTricksMadScientist]

The problem you are describing is called "Vapor Lock"

IT happens when the Brake Fuild is Old and gone Bad... Brake Fluid obsorb water and over time will become more water based causing the Vapor to expand and contract with heat, or by simply using the brake!!!

I learned about this the hard way, just like you are... only my problem was the dip**** at the dealership put powersteering fluid in the MC. Overall cost of repair was over $3k.... this was before I learned to do my own work!!!

Anyway... you should take the system apart (pistons, calipers, hardlines, etc) and clean all the metal parts (insides) with Brake Clean... do not get this on the Ruber, you may need to get new SS lines and a Caliper Gasket Rebuild kit, as the old ones are now contaminated! Before putting the MC on the Booster... there is a small Plunger that you can adjust... its about 1 6mm or 8mm dome top nut directly in the middle of the Booster... you may only need to turn it 1/4 rotation out (Lefty Loosy)... This is commonly overlooked when doing the 1-1/16 MC swap. Adjust it a few times to get it exactly where you want it. You should use BRAND NEW Brake Fluid... I only trust 2 types of DOT 4... Motul RBF-600 and the Endless line. These two have high Boiling Points (Wet and Dry).

Dont use or mix Fluids that are not in there original containers, or if they have been run through the contaminated system. Dont use Plastic containers or Cups to catch Fluid being passed through when bleeding the system!! Brake Fluid is VERY COROSIVE and disolves plastics, and becomes contaminated very easy!!

-Drew