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i have a 76 280z.i have to put brake fluid in the car about every two days.i don't know where it goes i have checked the hole system for leacks and can't find one.can any one tell me where it might be going.it is only the front brakes that i have to fill up.the brakes do fill spongy.thank for the help ahead of time
 

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Hard to say where your leak is, but you DO have a leak. Could be into the Master Vac Canister located behind the Master Cylinder Pump. Could be that one of the lines is holed and it is a small but persistent leak.

Since you've isolated the leak to the front half, get in there and start looking. Sorry, wish I could give you more than that, but as it stands that's what you have.
 

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this was happenign to me a while ago. Not as quick but about every week or two it needed to be filled.....

It turned out there were small cracks inthe flexible lines. They didnt appear to be leaking but after changing them the problem was fixed, so it must have been them....

Some other things to look out for.....

The seal wasnt working properly on the master cylinder on one of my cars. If you got someone to push the brake down you could see like a mist of brake fluid come out from the join. (I put a bit of paper under it pushed the brake then could see tiny little brake fluid dots on it.)

It could also be easy to think you are topping up the front when you are topping up the back. It looks kinda the wrong way round.
 

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Some brake cylinders the front resevoir is for the front brakes, some the front resevoir is the rear brakes. Determine which one you have. The rear brake shoes and all the brake dust in there can sponge up a lot of fluid before the leak shows on the outside, pull all 4 corners of your car and check closely. If everything is dry than you probably have a bad master cylinder. It can leak into the vacuum canister. I might also add check all the steel lines, they rust and it's very common to get one thats weepy leaky dribbley. Check all fittings and the rubber hose as well.
 

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M.C.

Mine is identical. Lots of time the large reservoir is the one that goes away. If this is to the rear of the master cylinder, then the fluid can leak out, into the master vac, and when you start the car it gets sucked into the engine and combusted...
The large reservoir is for the Front brakes ALWAYS, as the discs require more volume to actuate than the drums do. THe big reservoir is for the front, that's the theing to rmember.
They are correct in saying some have front/front layout of the master cylinder, some don't. I have cars with both. On the one where the drum section (small reservoir) is in the rear, IT leaked into the master vac regularly. Drove me nuts because the wheel cups out back were consistently dry!
I think there is somehow the vacuum in the Master Vac can leak towards the master cylinder and work majic on the master cylinder sealcup assemblies in the nearest portion of the thing. Just my theory, but I've never had the front half of the master cylinder fail.....EVER. Not on a Dutsun.
 

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Hey! Just Pulled Mine!

It was, AGAIN going into the Master Vac.
I was in the same situation as you---had to fill the reservoir every day, but no leak under the car!
Pulled the M.C. off just a while ago (see post: "Terrible Stock EFI"...) before doing some runs, and found all sorts of nasty leakage into the Master Vac.
Like I said, AGAIN! But when you got 9 Z's, and five are road worthy, you go through some parts...
 
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