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Quick Master Cylinder Problem/Q


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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

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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.

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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.

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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?

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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.

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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.

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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.

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  • 3 weeks later...

??? 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.

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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.

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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.

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