Armand Posted August 25, 2007 Share Posted August 25, 2007 Hey guys, I'm just re-newing my stock brakes. Put hawk hps pads up front, new shoes in the rear, stainless steel brake lines all around, but I have a problem. When I tried bleeding the brakes it wouldn't hold a vacuum. So I checked out some stuff and found my master cylinder had a small leak. I looked around for an original mc but the only ones I found were like 240 bucks. So I put in the larger '79 280ZX mc. I also found my check valve was bad but I replaced that with a brand new piece. So right now my problem is my pedal has no firmness to it whatsoever. It's completely loose right before it hits the floor, toward the end of the pedal throw I can feel I'm just pressing the brakes with purely my foot power. When I do feel the brakes its extremely weak and I have to really push on the pedal hard to make the car stop. The brakes are bled perfectly but the pedal just hits the floor. My question is if the larger 280zx mc is causing this. When I first ordered the part I thought that it would be the opposite, I thought the pedal would feel even firmer with the larger mc. But is the larger mc w/ stock equipment causing this problem? Or is my problem elsewhere? I'm a 16 year old and I have no education or anything when it comes to cars. I only read what I can find online and in my repair manuals and try to figure out the rest. Thanks in advance, -Armand Quote Link to comment Share on other sites More sharing options...
Armand Posted August 26, 2007 Author Share Posted August 26, 2007 I just discovered that when I push the pedal I can hear gas escaping. So that's what's making the brakes have no vacuum. What I'm wondering is where can there be a leak? The MC is brand new and the booster is all good. No leaks in any brake lines anywhere. Quote Link to comment Share on other sites More sharing options...
zachattack15 Posted August 26, 2007 Share Posted August 26, 2007 Have you adjusted your rear brakes? Quote Link to comment Share on other sites More sharing options...
Armand Posted August 27, 2007 Author Share Posted August 27, 2007 Yes, my rear drums are perfect. All the brakes are functioning just fine, its just there is no vacuum. I think its my booster because I just noticed the hissing sound from the booster area when I push the pedal. I have a rebuilt unit somewhere in my garage. I'll try it out tomorow. Quote Link to comment Share on other sites More sharing options...
zachattack15 Posted August 27, 2007 Share Posted August 27, 2007 Im not sure on the Z. But most master cylinders have a rubber o-ring on the backside of the master cylinder where it meets the booster. Do you have that o-ring? If not that could be your problem. Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted August 27, 2007 Share Posted August 27, 2007 search for "reaction disk" as well Quote Link to comment Share on other sites More sharing options...
z-ya Posted August 27, 2007 Share Posted August 27, 2007 If there is a hissing sound around the booster, then you need a new brake booster. They are around $200 from Black Dragon Auto. I just put one in my turbo car. Quote Link to comment Share on other sites More sharing options...
Armand Posted August 27, 2007 Author Share Posted August 27, 2007 I bought one locally for $130, it's a rebuilt A1 unit. Looks like a really nice piece. I'm gonna install it today and I'll update you guys. Thanks for the help. Quote Link to comment Share on other sites More sharing options...
mario_82_ZXT Posted August 27, 2007 Share Posted August 27, 2007 Did you bench bleed the master cylinder before installing it? Mario Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted August 28, 2007 Share Posted August 28, 2007 Did you bench bleed the master cylinder before installing it? Mario Yeah, that alone takes about 20~30 minutes. (Just did mine) Quote Link to comment Share on other sites More sharing options...
zachattack15 Posted August 28, 2007 Share Posted August 28, 2007 20-30 min? NO way! I do it everyday for work and it takes me a few min max Quote Link to comment Share on other sites More sharing options...
Armand Posted August 29, 2007 Author Share Posted August 29, 2007 Alright, so I installed the new brake booster. Hissing went away, put the pedal still drops straight to the floor. I tried thinking what else could be wrong, its got a new mc, new booster, new stainless lines, no leaks anywhere, everything bled perfectly. So I realized that the 280zx mc was larger so I figured I should adjust the push rod a turn or two out. But this thing is just budged on there! No matter what I did this thing wouldn't budge. I tried searching HZ and google, and I found that since the push rod can't be moved the slightest bit, sometimes there is a very very strong locktite used on the threads when assembled. Is this my problem? How the hek do I get this thing loose? Quote Link to comment Share on other sites More sharing options...
z-ya Posted August 29, 2007 Share Posted August 29, 2007 Pull the MC away from the booster, and look at the rod in the booster. There are two different lengths. They are also adjustable. The tip unscrews so that you can remove and or adjust it. So you can either swap the tip from your old booster, or adjust the one on the new booster so that it is the same length as the one you replaced. Quote Link to comment Share on other sites More sharing options...
Armand Posted August 31, 2007 Author Share Posted August 31, 2007 Problem Solved! Push rod needed to be adjusted plus the reaction disk was out of place. Dumba$$ mechanics at the local brake shop don't even know how to install a booster. My brakes are GREAT! With the new pads, new SS lines, new brake fluid, new larger master cylinder, new booster, re-adjusted rear drums, the pedal is sooo stiff with almost no fade whatsoever. Stock brakes kicka$$ when setup right. Its great because I can slam on the brakes with no locking up on any wheel. It just STOPS. My interior is almost finally completed so I'm really excited. Quote Link to comment Share on other sites More sharing options...
z-ya Posted August 31, 2007 Share Posted August 31, 2007 Stock brakes kicka$$ when setup right. Its great because I can slam on the brakes with no locking up on any wheel. It just STOPS. My interior is almost finally completed so I'm really excited. Exactly! For street use, the stock brakes are more than adequate. Good to hear you got it figured out. Quote Link to comment Share on other sites More sharing options...
G.I.jonas Posted September 21, 2007 Share Posted September 21, 2007 ??? im a bit concerned here as your brakes SHOULD be able to lock.Also how can you say everything is done perfect and then after say that you say I'm a 16 year old and I have no education or anything when it comes to cars. I know thread is 3 weeks old but you may need to look at those brakes still. Quote Link to comment Share on other sites More sharing options...
Armand Posted September 21, 2007 Author Share Posted September 21, 2007 I haven't really SLAMMED on the brakes as hard as I possibly can but pushing it pretty damn hard the car just stops and I can feel its on the verge of locking up. I don't see why I would try to setup the brakes to lock up. Plus what I really like is it isn't a one wheel lock up. It tracks perfectly straight under HARD braking, and I know if it were to lock up it would be both left and right wheels at relatively the same time. Comparing to how the brakes were before the problems started I'm VERY happy and I'm pretty sure this is as good the stock brakes get. Quote Link to comment Share on other sites More sharing options...
G.I.jonas Posted September 21, 2007 Share Posted September 21, 2007 I don't see why I would try to setup the brakes to lock up. Its not a matter of setup,just saying that if you dont have any problems with your system and there isnt any air in the lines your brakes will lock,Think of locking as evidence of having done it right,not to say that you should do it all the time. Quote Link to comment Share on other sites More sharing options...
Armand Posted September 23, 2007 Author Share Posted September 23, 2007 Btw, I tried slamming on the brakes and yes I did lock up the fronts. Quote Link to comment Share on other sites More sharing options...
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