Anyone know their brakes inside and out? Need some help.

[ninJAPANda]

So I posted a request for help a while back having to do with Brake Bleeding and a few people answered, but nobody really told me exactly how to brake bleed.

I took it to my local garage after not being able to figure out what was wrong with my bleeding procedure for the longest time. It turns out there might not have been anything wrong with how I bled it. The guys at the garage resurfaced my rotors, tightened and checked all of my brake lines for leaks, and vacuum bled it themselves.

After all that, it turned out that as soon as you step on the brakes the first time, they're fine. But subsequent use of the brakes after that would somehow let air in and they would become mushy again. Like stepping on a sponge. Unless I pump my brakes up a couple times before I fully apply them, the pedal will bottom out and I will lock wheels and hear some god-awful grinding going on near the front of the car. Still not sure what's up with that.

Anyway, the mechanics there told me it could be the Master Cylinder that's suffering internal leaking. Since I'm not losing brake fluid (no leaks) and the system has been bled at least 10 times (the last two times by professionals) I am willing to believe they are onto something.

I just wanted to know if anyone else has ever had this problem and would very much appreciate any light you guys and gals could shed on this, seeing as brake MC's are stupid expensive...I know I shouldn't mess with the brake system and take risks, but I want to be sure before I make another useless (and expensive) step in fixing my brake system.

Thanks in advance

[REDWINTERZ]

Here is the brake bleeding procedure if you're still interested:

http://www.ttzd.com/tech/lines/lines.html

Not sure about the grinding noise though. Weird. Good luck!

[Sgt]

Does your Z have ABS? Has it been working? Any check/warning lamps?

Here is a routing line of the lines: http://www.300zx-twinturbo.com/s.manual/br/004.gif

I am wondering if the ABS actuator may be malfunctioning internally causing pressure loss.

Where is the grinding noise coming from? Is it in the rear of the car?

[REDWINTERZ]

He said the front I think... on the ABS though.

[kapower240]

Maybe you can try rebuilding the master cylinder instead since it's cheaper. You can find rebuild kits online.

[robomatic12]

The solid brake pedal feel and then a sudden loss of pedal feel points most likely towards a failing/failed brake master cylinder. Do not mess around with brakes, they are what's preventing you from going 60+mph into a wall. Just buy a new or professionally rebuild master cylinder. A lot cheaper than buying a new car and you can't buy a life. The master cylinder seals are shot allowing air back into the system.

Not too sure about the grinding noise, are you used to the sound of tires locking up? Are all your caliper pins greased and the brake pad shims installed?

[Sgt]

I am inclined to agree with the master cylinder theory. Parts aren't that bad.

OEM Master Cylinder (1991-1996) $258 : http://www.conceptzperformance...IS300

Centric Master Cylinder (1991-1996) $170 : http://www.conceptzperformance...IS300

OEM Rebuild Kit $65 : http://www.conceptzperformance...IS300

[ninJAPANda]

Hey guys,

Much appreciation for all of the help.

Sorry I'm replying kind of late, but I been sick this weekend. Ridiculous...I sound like a frog.

Anyway, I have tried following the TTZ's of Dallas guide as it is the same one as the NICO technical article about stainless steel lines. I've tried following the manual, I've tried a lot.

I do have ABS, and when I bottom out on the pedal with the first pump it feels like the wheels lock a bit, the front "grinds" (I don't lock my wheels much but I'm pretty damn sure that's not the sound wheels on pavement makes when they rub) Pretty much, feels like something is being scraped in front with an awful grinding noise. At the same time, the ABS actuator goes nuts and I hear it buzzing...I think I forgot to mention that last time.

Now if I do pump the brakes a few times, ABS seems to work fine. I've tried some hard braking and as long as the pedal doesn't bottom out it seems to control my grip of things. Otherwise, I forget to pump up the pressure and the grinding, sliding, and buzzing commences.

Sounds like either the MC or the ABS Actuator could be the culprit, but I don't understand the ABS system that much at all, so I wonder if someone could elaborate or further pinpoint my problem now.

In the meantime, I am not driving much and definitely not tailgating as close.

[k3vin0615]

Hey bro I kinda have the same problem when I step on the brakes I have to press hard to stop but the pedal is really soft and I hear a loud grindin noise comin out from my right front wheel I kno its not the abs nd u can feel the right side shake a little...I took it to the mechanic nd all he was tht I needed new rotors..I bought new rotors nd hawk pads im gettin them replace today hopefuly tht will fix my problem

[ninJAPANda]

Hey Kevin,

Your problem might be a little different. It's possible it's simply the rotors causing all of the trouble. Since your grinding is from one wheel, it could be your pads grinding that rotor.

The shaking is definitely coming from a bad rotor surface. Stopping at high speeds will introduce a severe shake in your steering wheel. I got my rotors resurfaced so I'm ok for a while.

If you are going to get stuff replaced, I'd get both fronts replaced, obviously, to keep things even. Hawk pads are pretty damn good...I'm running them right now, and if my hydraulic system weren't so effed up I could stop on a dime...

Good luck with your stuff man.

[nsrZ32]

I'd lean towards a master cylinder as well

[Touge-Z32]

Did you check the brake booster check valve?

I had a similar problem where my brakes were spongy and shaking. So I rebuilt my calipers and put new stainless steel lines, pads, and rotors but it didn't fix the problem with the brakes being spongy. I found the valve insde a plastic clamp above the brake booster, so i checked and it was bad. After I replaced I stoped like a champ and hopefully it's a simple fix as that for your problem.

The easy way to check is to blow into the booster side and if any air passes through it than change it out.

Part Number: 47478 http://www.courtesyparts.com/3....html

Also if you really want to bleed the brakes again do it in this order which I didn't do the first time. Left rear, right front, left front, right rear, ABS actuator front, ABS actuator rear. Repeat this order until all four corners are clean & air free http://www.ttzd.com/tech/lines/lines.html

[alright2020]

if the pedel sinks to the floor then its a bad master cyl... you can pinch off the lines and push the pedal to test it.... if it still sinks to the floor then its a bad master

[robomatic12]

Did you check the brake booster check valve?

I had a similar problem where my brakes were spongy and shaking. So I rebuilt my calipers and put new stainless steel lines, pads, and rotors but it didn't fix the problem with the brakes being spongy. I found the valve insde a plastic clamp above the brake booster, so i checked and it was bad. After I replaced I stoped like a champ and hopefully it's a simple fix as that for your problem.

The easy way to check is to blow into the booster side and if any air passes through it than change it out.

Part Number: 47478 http://www.courtesyparts.com/3....html

Also if you really want to bleed the brakes again do it in this order which I didn't do the first time. Left rear, right front, left front, right rear, ABS actuator front, ABS actuator rear. Repeat this order until all four corners are clean & air free http://www.ttzd.com/tech/lines/lines.html

It appears to be more common to go from furthest from the master cylinder towards the nearest and then bleed the ABS actuator nipples (if you have them, certain years dont). IMHO just what I've been taught as a tech.

If you are LHD: RR, LR, FR, FL, Rear ABS, Front ABS

[ninJAPANda]

Hmmm. So I'll probably get a new MC soon and go from there. I'm a full time student, so it may be a while...

As for the bleeding procedure, I read somewhere that certain Z's have a criss-cross line system of some sort for the brakes which is why they criss cross in the bleeding pattern....unless I dreamt that up. Not sure why else they would order it that way.

Anyway, with order aside, the main problem I had with bleeding was the ABS actuators....I have them...I know where they are....problem is they don't have motherflipping bleed nipples....so wth am I to do?

Although I've tried bleeding it and had it bled by others, I never once assumed that anyone did it correctly yet, so bleeding advice is always welcome. It may serve useful in the future anyway...

But yeah, MC, then re-bleed with what i know by then. And hope to the Nissan gods it works or else I not only won't know what to do, but will be quite pissed at having spent the money for a new MC without really fixing anything.

Main question now: Anyone know what to do about ABS actuators with no bleed nipples? Only thing I've heard and pretty much only thing I can think of doing is to keep bleeding the calipers until its clean. Not sure it's possible to get it air-free that way though.

[Touge-Z32]

I would first check out the manual check list to see what can be causing the exact problem and follow the procedure. Sometimes it might be something else as you might be replacing a perfectly good part and the problem could arise again.

From TTZD http://www.ttzd.com/ The ABS actuator on 94+ (9.) doesn't have bleed nipples, so I'm not sure how that works out. I bled the brakes on my '95 for a while until the 'gurgling' noise went away from the ABS actuator while bleeding it. '90-'93 have the nipples

I need to state that the bleeding procedures that I posted up is right off the 300zx mechanics manual. Brake Section page 5

http://www.300zx-twinturbo.com/cgi-bin/manual.cgi

[robomatic12]

I stand corrected Touge! Looks like the Z does have a different criss cross bleeding pattern and yes if you do not have bleed nipples just ensure there is no air coming out during bleeding.

If you end up buying a new MC, make sure you bench bleed it properly. Don't push the piston too far in or else you can damage the seals and ruin it. This is because your normal brake pedal travel is much less than what you can apply with a blunt tool in a vice.

Only other things to check would be that the bleed nipples on the front and rear calipers are on top of the caliper. If installed on the wrong sides they will never bleed correctly. Re-check for any leaks, trace all brake lines.

Goodluck!

[daga480]

Sorry to bump this old thread but my car has this exact same problem and some of the best Z mechanics around haven't been able to solve it so I'm hoping OP sees this, has fixed it, and can help me out. It has been bled many times, including the ABS, BMC/booster have both been replaced, as has the check valve multiple times, and new calipers have been checked as well.