I am at my wit's end with these brakes!

[madkaw]

Man this is just like the deal I had with my Mustang-yes it was frustrating!!

I guess it's possible that your MC was going bad and you replaced it with another bad one or the WRONG one. The MC rod should be checked for sure. With the wrong mating of MC and rod you would be coming up short on travel on the valve. I would be a bit suspicious of an Autozone MC. If you take it off-take it apart and look at it. Someone could have put a rubber on backwards. Check the general condition of the bore for pitting.

Don't underestimate the ability of air to be trapped. Like I stated before, I had to remove the caliper off spindle and let the pucks come out past their normal travel on some wood. When returning the pucks I watched the air come back into the MC-bingo!

[240Z-Fan]

[...] Don't underestimate the ability of air to be trapped. [...]

Yes! I had a car that I could not get a good pedal feel. I started to doubt myself so I took it up and down the local roads (I am in the country) to assess it better and presumably bed-in the brakes. It didn't take long for me to conclude it still had trapped air.

I then got home and cracked open the bleeders and for a second "nothing" came out, then finally fluid ran out quickly. I then closed the bleeders and gave it another check and it felt great. Problem solved. My guess is that the vibration and heat helped get the bubbles free for wherever they were and move to the top of the caliper.

[Travel'n Man]

@ Travel'n Man: Yep! It's a Fenco rebuild from Autozone: Fenco Reman/Master Cylinder (Brake System) (M51658) | 1976 Nissan/Datsun 280Z 6 Cylinders H 2.8L FI | AutoZone.com

If I could find the paperwork on it, it does have a lifetime warranty, and I could always make them deal with this instead of me!

I'm curious about the 15/16" and 1" master. Do you have any links I could read up about that on? I've toyed with the idea of going with discs in the back at some point in the future, but never took steps to actualize that. It would certainly fit within the Z -mantra of "Well since I'm replacing <x thing> anyway I might as well do..."

I'm already going to lose the check valve, and probably go with an aftermarket/universal proportioning valve, just to keep both circuits truly isolated from each other and keep things nice and simple.

... also, have I mentioned lately how much I hate flare fittings? haha

A One Inch Diameter Brake Master Cylinder for the S30 Z Cars - Brakes, Wheels, Suspension and Chassis - HybridZ

Help! What brake options are available for S30 Z cars? - Brakes, Wheels, Suspension, and Chassis - HybridZ

If you are looking for the best and easiest way to make flares (and don't mind to pay to rent a flare press form Fedhill) - this is the ticket without a doubt - a picture perfect flare every time - not sometimes - but every time dead on perfect. The second picture is from some of the flare that came from those cheap $40 tool sets - they just suck and no matter how good you are you can not duplicate the quality of a flare press. It really makes a brake job a lot easier and connections that will last for a few more decades. The Fedhill brake line was wonderfull to work with and never had a kink period. Great stuff! Hope this helps with your mission - enjoy the ride!

[Wade Nelson]

Another ZOMBIE thread come back to life.....might as well add my two cents worth.

If it's air in the lines, and the pedal works AT ALL, you should be able to "pump up" the pedal until it gets stiff.

If it's a leak in the lines or at a wheel cylinder no matter how many times you press the pedal it won't get stiff even with Viagra in the brake fluid.

If a system is sealed, it almost doesn't matter WHAT method you use to bleed it, they'll all work provided you don't allow the reservoir to run out of fluid while you're doing it. If there's a loose line, leaking cylinder, etc. almost NO method will succeed.

[Travel'n Man]

Another ZOMBIE thread come back to life.....might as well add my two cents worth.

If it's air in the lines, and the pedal works AT ALL, you should be able to "pump up" the pedal until it gets stiff.

If it's a leak in the lines or at a wheel cylinder no matter how many times you press the pedal it won't get stiff even with Viagra in the brake fluid.

If a system is sealed, it almost doesn't matter WHAT method you use to bleed it, they'll all work provided you don't allow the reservoir to run out of fluid while you're doing it. If there's a loose line, leaking cylinder, etc. almost NO method will succeed.

A ZOMBIE thread that is only 4 weeks old and the person that started it is still having a challenge - I don't understand the comment.

[Wade Nelson]

A ZOMBIE thread that is only 4 weeks old....

How little you know about Zombies! There are "newborn" Zombies and centuries-old Zombies!

When I scanned the thread I got the impression the problem was fixed.... BUT...

WAIT FOR IT.....

"Suddenly the squishiness in the brake pedal has returned.

IT'S A ZOMBIE PROBLEM!!!! IT KEEPS COMING BACK TRYING TO KILL THE OP.... (by way of no brakes!)

Remember, "ALWAYS AIM FOR THE MASTER CYLINDER!!!!!"

Edited June 2, 2013 by Wade Nelson

[KDMatt]

Oh goodness, I didn't see that this thread had still more replies after my last one.

... and no, this isn't a "Zombie Thread" as I am still very much in the throws of frustration!

I apologize that I haven't been keeping everyone up to date here, but I've been swapping ideas with some of my local Z guys to get their two cents on this.

The general consensus was that we shouldn't completely rely on the Autozone MC, so I ordered the $160 one from MSA.

I also decided that I didn't want to risk the possibility of air leaking in through either the proportioning valve nor the check valve, so I ditched those as well. I now have the front brake circuit running off of a T-fitting, split directly from the master cylinder, with a 10mm union uniting a couple of the pieces of line.

For the rears I got an adjustable, inline proportioning valve.

Also, T-Man, to avoid using the cheapie flaring tool I have, I ended up just buying a lot of pre-made brake lines of differing sizes to do this work, just to make sure the flares were solid.

So, now, I've got all of this new stuff on there... bled the crap out of everything. I even bought a special tool for bench bleeding the master. Everything is coming out totally clean, bubble-free, and fresh looking. I can hear and see the brakes engaging, and yet the pedal still feels super soft.

I'm still picking the brains of my local chapter of guys, but at this point I'm really starting to lose faith in this car.

I know I said I'd take off the brake booster, but I never did get around to doing that. I removed the air hose going to it because the reversed air coming out with each pedal push was making this horrible groaning noise in the check valve. I'm guessing it's normal for air to flow out of it when the pedal is being pushed down?

Should I try pulling off the calipers and letting the "pucks" (as one previous poster referred to them as) run out, and then squeeze them?

I'm getting close to that point where I either need to get it towed to a qualified brake shop and let them deal with it, or I'm just going to part it out, sell it, and just be done with my 8-year Datsun love affair. The brakes on this thing haven't been "right" since Fall 2011.

Edited June 20, 2013 by KDMatt

[madkaw]

Should I try pulling off the calipers and letting the "pucks" (as one previous poster referred to them as) run out, and then squeeze them?

That was me. Pull the calipers leaving the hoses attached. Remove the pads and use a piece of wood or something to simulate the rotor. Your shooting for getting the caliper pucks beyond their normal travel. Depress the pedal to get the pucks out on the wood.

Now- Making sure you have the lid off the MC, reset the pucks slowly back in place. If you have any air. you will see a milky bubbly mix come up.

I went thru all this on a 69 Mustang with the same level of frustration and 2 MCs. A friend suggested this and it worked. The right front caliper was the culprit. I guess the air was trapped and being bypassed during typical bleeding

[KDMatt]

@madkaw: Should I try to force it back up to the master, or should I be cracking open the bleed screw to do it?

[madkaw]

Just slowly force the pucks back in - just like putting on fresh pads

[KDMatt]

Update:

@madkaw: I pushed the fluid through the system backwards and got clean results at the master. So as far as I can tell, the lines are bled and A-OK.

Here's an interesting development however, and see if you guys can follow me on this one.

I remember reading a while back about the adjustment of the pushrod from the booster to the master, and that one of the symptoms of having one adjusted out too far was premature brake locking (i.e. while driving), and that the only way to fix the system was by relieving pressure in the master.

Seeing as my symptoms are essentially the opposite of this problem (i.e. won't lock at all, and seeming lack of pressure in the system) I figured there was no harm in fiddling with the pushrod.

I adjusted it out a pretty significant amount (don't worry, it's marked so I can put it back the way it was originally if need be), and to my surprise (if not amazement?) the pedal began to feel much more like I remembered it feeling long ago.

What's more, when I took the car for a quick spin I was able to get the brakes to lock when I slammed on them, which was something I was completely unable to do before.

I'm starting to think perhaps I did lose my reaction disc after all, and the adjustment of the pushrod outward is just compensating for the distance lost.

I'll fiddle with it a bit more (certainly as my adjustable proportioning valve seems to need, well... adjusting), but I'm curious to hear your guys' thoughts? Does this seem like a plausible explanation?

I still find it odd that my pedal travel was met with some resistance all the way through its travel before, but then again this is all pretty new territory for me. I just want to make sure that if this does indeed rectify my issue, that it isn't only masking what might be a more serious, latent problem.

Thanks for sticking with me, guys!

[KDMatt]

Final Update: I think I've got her fixed!

I took a break from the car for a while, went out of town, came back to it, tackled the issues one more time, going slowly and methodically, and I have finally achieved the results I was looking for.

As it turns out, I had not just one failure/error, but two, if not three, all of them cascading on one another to make my life a living hell for the better part of a year.

So as to, in a way, "conclude" this thread, I will go through everything that went wrong.

The first ingredient was the rear brake cylinder that popped its seal. The rubber tore and leaked out all of the brake fluid, which in turn prompted me to replace both rear cylinders, and brake shoes.

Error 1: It was only recently that I realized I did not have the new shoes adjusted properly, even though I honestly, truly, thought I did.

In bleeding the new cylinders I came to the conclusion that my old master cylinder wasn't moving enough fluid, so I replaced it.

Error 2: Pulling the pushrod out during the replacement of the master cylinder, which I did twice! ... because...

I finally crawled underneath the dashboard and did the contortionist thing to pull the brake booster out of the car.... and sure enough...

Error 3: The reaction disc had fallen out.

So, in conclusion, it was ultimately a combination of mechanical failures combined with a healthy dosage of inexperience on my part that led to creation of, and prevented my recovery from a seriously bizarre concoction of symptoms, caused by a combination of problems and oversights. I am very confident now that I have rectified the problem.

Even though this thread has been a couple of months in the making, I just want to thank everyone that contributed and kept me encouraged. I kind of have my foot in my mouth a little bit on this one too, but those of you shaking your head at me can at least take some solace in knowing that I probably spent a lot of money on this project I didn't really need to! :stupid: Live and learn I suppose!

Cheers, everyone!