This Is Driving Me Crazy Now!!!help

[zdriffter]

hello my Z brothas. First of all i want to thank all these people on hybrid that have provided lots of helpful information on here. Good job guys. Anyway this is my problem.

 

I have 1973 240z. This car sat for lilke 10-15 years before i bought it. So i bought it did turbo swap, suspension, ect... Well i did the 4runner caliper upgrade non vented, stock rotors, got the booster rebuilt @ napa, replaced wheel cylinders, got the msa steelbraided hoses all around and well the master cylinder i had the stock 240z one but swap and put i believe 280zx master.

 

Heres the prob. The pedle is very sensitive and soft. Ive bled it several times and still the same thing. Its hard to explain exactly how the peddle feels all i can say is that its very sensitive and soft. I been driving the car like this for a while now but now ive had it. I want to fix this prob but dont know where the problem is at????? The car stops, there is a point where the peddle stops and if i have to stop fast then i have to push on the brake really hard for it to stop completely. I dont know if when i took the booster i had to adjust the shaft a certain way before installing it back. Alot of people have told me it can be the porpotioning valve but i dont know. I really need help on how i should run this 4 piston 4runner caliper set up.

 

1) can i use the stock 240z master cylinder?

2) should booster shaft be adjusted certain way?

3) Do drums brakes have anything to do with my prob? not adjusted right?

4) Should i go back to the stock 240z calipers?

 

Any info or tips would help guys. you can email me @ bre240z@aol.com.

thanks jimmy

[Guest 280ZForce]

this actually happens to alot of us w/ any brake changes...so dont be surprised.

 

i would definately upgrade to a zx brake master cylinder though.

 

when i had my pads changed in the front and did a disc conversion in the back i ran into the same problem...must've bled the lines 30 some times and removed/reinstalled the bmc and what not before it fixed itself.

 

if u pump the brakes while stopping does it help? like pump once and then the 2nd time it's firmer to push in?

[Mr.INSANE]

sounds like bad Master Cylinder to me

[zdriffter]

no peddle feels the same even by pumping them several times. Its just very soft and sensitive. Dam im even thinking of going back to stock set up. I dont see any possible leaks anywhere.What im planning to do is replacing the master cylinder with a new 280zx, the booster...well i dont know if i have to re-adjust the shaft, and putting the stock 240z calipers back on rebuilt. What do u guys think??? thanks for the info

[blueovalz]

"soft and sensitive".... hmmm, sensitive implies (to me) that it will lock up the wheels very quickly with no modulation, but you're saying you must push hard on the pedal to stop the car. There are some strings from the past (search will help) about the reaction disc in the booster. You may want to investigate this if you're sure the air is completely out of the system.

 

Several members have had bad master cylinders right out of the box (including me), and some have just simply not done the bleeding correctly (MC outward toward the wheels), and others have had the reaction disc slip out of place and fill into the diaphram chamber (easily fixed, but you'll need to find the string, being I've not had to do this and I did not pay real close attention to how it was done or fixed)

[zdriffter]

ok ive found some threads w/ similar prob that i have. The reaction disk in the booster maybe have fallen out. Ok now how to i check if its no there? And if it did fall off is it possible getting it out of the booster? How hard is it to see if its fallen out of place.

[zed240au]

just my 10 cents worth i ran std 240z booster and master cylinder throught two brake upgrades and its still feels fine so id be inclined to try the 240z master cylinder first

I first ran 240z calipers with good pads std rear

2nd hilux 4 spot calipers on std discs std pads and then good compound pads and mazda 929 rear discs

3rd hilux s12w calipers carbon pads on vented discs and mazda 929 rear discs

 

so i reckon the 240z master cylinder work fine and ahs felt good through all my changes

[Trevor]

and mazda 929 rear discs

Hello Zed240au,

Tell us a bit more about this modification. Are these rotors vented? What make of caliper did you use? Is there a custom bracket required?

 

Thanks,

[evildky]

he said he has to put the pedal to the floor to stop, I think my sensetive he means that the pedal requires very litte effort to move, that being said, sounds like the master cylinder

[240playtoy]

If you removed your M/C from your booster, it's very possible your reaction disk fell out.

Reaction disk missing (follow link to see pictures): Sensitive = push it down a long distance with little slowing of the vehicle then poof, wheels lock up.

To take the booster apart to find the disk missing was very easy, but maybe my booster was ready to fall apart to begin with. The actuating rod on the M/C side just pulls out along with the "retaining" piece (round piece in front of the plunger in the pics on the link).

As for soft, I had that issue as well but it went away after I replace my missing reaction disk.

[1 tuff z]

sounds like the reaction disc to me. i just went thru the same thing. here's what the disc looks like.

 

http://album.hybridz.org/showphoto.php?photo=7428&cat=500

[zdriffter]

Guess what it was the reaction disk..... dam thanks to this site, i had been trying to troubleshoot this problem for the longest time. Sure enough when i took the m/c out and the shaft wala! that dam disk was gone. So i manage to take it out of the booster put lil bit of silicone to hold it in place reinstalled everything and bam now shes stops beautiful. Thanks guys.

[1 tuff z]

it took me about an hour to actually get the booster 'split' apart. the shop manual instructs you to use the special tool-mine consisted of 2 very large screwdrivers. anyway, here's what i did. remove master-leaving the aluminum plate attached to the booster. remove booster, then clamp in vice-clamping on alum plate-use vice jaw protectors or something suitable. use some penetrating lube around the circumference of the seam where the 2 halves join. tap-around the outer portion with a rubber mallet to help 'loosten things up a bit'. then, take the large screwdrivers or levers and position them in a manner that you're attempting to rotate the non-clamped half counter-clockwise. it's a tough nut to initially crack and only needs to turn about 1/16 of a turn. be sure to index mark it first or take pics for reassembly. once turned it simply pulls apart. then it's easy. i called the dealer this morning, they still sell a 'rebuild' kit for it-they're around $100. i believe bonzai still carries the stickers if interested.