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Brakes have me lost...


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Hello,

 

I am lost on my all stock brakes on my 1977 280Z..so here it goes...I replaced all of the rear drum components, the front calipers, rotors, pads, soft lines are now steel braided, brake booster and the master cylinder...so with that, the rear brakes work well but the fronts require that I pump the pedal a bit to engage...I have bleed and bleed them and no improvement...I can't find any leaks, except on the forward most brake line that comes right off of the master cylinder...I tightened it and have got it to stop leaking for the most part, the pedal has no firm feeling at all with the car on and it has some resistance with the engine off but can be pushed all the way through its travel...any help or advise would be greatly appreciated...

 

Alex

Edited by Volition77
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 but can be pushed all the way through its travel

Can you pump up the pressure by lifting and pressing the pedal repeatedly?  If they can be pumped up and will hold, then you have air in the system and need to find a way to bleed it.  If they can't be pumped up then you probably have a leaky seal in the master cylinder.  Did you take the MC apart and clean it before installing it? Today's manufacturing standards are poor and rebuilt parts are often dirty,with honing grit inside that can damage the new seals.

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So you have a split MC, correct? If so, confirm that the front reservoir is connected to the back brakes and the back reservoir to the front brakes. Front brakes get the larger reservoir.  Also confirm that the MC is for a 280Z and not a 280ZX.  The 280ZX MC is designed for disc brakes in the rear and will cause you issues if you have drums.

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  • 4 months later...

Sorry to take so long to reply, I moved and took forever to get things set up again. cgsheen, I will try to bleed again using the method you mentioned, thank you. And Phantom, I do have the split MC, I can't comfirm it's for either, I just ordered it through an Advanced Auto type place...So it could be wrong...I will look into it, thank you.

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I had a brand new brake system with new hard lines, masters, calipers, whole deal and had a hell of a time getting a pedal. What finally worked for me was using a syringe and pushing fluid from the bleeders back towards the masters. That finally got it. I guess motorcycle shops bleed this way all the time. I used a 60cc syringe and just put the bleeder tube right on the syringe. Looks like this one:

http://www.calvetsupply.com/product/Syringe_60cc/Syringes_and_Hypodermic_Needles

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http://www.xs650.com/forum/showthread.php?t=11205

 

I use the oil can method in this link.  Works pretty good.  And it's a lot cleaner.  Make sure you use clear hose too!  A few times I've used regular black hose and I could never see if I had the bleeder opened or not, and pressurized brake fluid hit me in the face.

 

Not a fun feeling.

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I had a brand new brake system with new hard lines, masters, calipers, whole deal and had a hell of a time getting a pedal. What finally worked for me was using a syringe and pushing fluid from the bleeders back towards the masters. That finally got it. I guess motorcycle shops bleed this way all the time. I used a 60cc syringe and just put the bleeder tube right on the syringe. Looks like this one:

http://www.calvetsupply.com/product/Syringe_60cc/Syringes_and_Hypodermic_Needles

 

I just discovered using a syringe while bleeding  a clutch master cylinder. I got the 60cc syringe from kitchen supply section of my local super market (hardware store has them also). The syringe  comes with a needle that  can be fitted into clear plastic tubing.   For new brakes I use a Motive pressure bleeder (like a garden sprayer)  initially to fill the system and have added speed bleeders to the MC and calipers to make follow-on bleeding easier. The syringe comes in handy to fill/remove fluid in the master cylinder.

Edited by Miles
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Going back to your original post you say "...have got it to stop leaking for the most part"

 

Maybe this is the problem, the brake hydraulics have to be a completely closed system; any small leak will suck in air so there's not really any point doing anything else until you've fixed the leak properly.

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JMortensen, ihiryu and Miles I will give those inputs a try for sure, I just hate not getting any pressure/feedback in the pedal, I flipped the check valve to see if that was installed the wrong way, I don't think it is the problem as it will only let air through one way, so I assume it is functioning properly...and morbias, you are correct for sure, I just took the car for a drive around the block with plenty of braking and the lines where I thought it was leaking were bone dry...So I am really just stuck on no brake pressure in the pedal...The brakes stop hard when the pedal is pretty much to the floor but not until just before bottoming out...Could it be on the booster back side, where the pedal connects, needing to be shortened down so the pedal can actuate the rod for a longer travel? Thanks for the help guys

Edited by Volition77
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That sounds like a reaction disk issue. Search here and classiczcars.com for "reaction disk" and see if that sounds familiar.

 

When you check to see if the "reaction disk" has fallen out of place, also verify that the push rod that goes into the master cylinder is adjusted to the correct length per your Haynes or Chilton or Factory Service manual. Make sure that the reaction disk is in place first and then adjust the push rod. Do a search on push rod adjustment for the details. If you find  the reaction disk glue it to the push rod to avoid it falling off the next time you have to remove the master cylinder.

post-178-0-33703400-1433908201_thumb.jpg

post-178-0-18826000-1433908216_thumb.jpg

Edited by Miles
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