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MapleNuts

610 brake upgrades issue

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Alright here’s another one for you guys. II got a brake problem. On my 610 recently upgraded to 280zx front calipers with 7/8 master cyl. All brake parts are brand new including wheel cylinders. Original booster.

 

Brakes are hard when cars off and when on I have almost 0 brakes. Foot goes to the floor. When bleeding fluid flows through the calipers a good strong amount.

 

Looks like the 7/8 over the 3/4 BMC has about a extra 1/4in of pushrod length.

 

Is this difference my issue or proportioning valve? Or booster related?

 

Also when I slam on the brakes with engine on the brake light comes on.

 

Thanks guys.

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I have that same setup without a booster and i think i had to lengthen the 7/8 master cylinder pushrod.

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Brake light on when slamming on the brakes indicates that either the fronts or the rears are not building pressure properly. If fluid flows when bleeding the calipers, suspect the rears.

 

I assume the rears were bled properly? If you didn't bleed them it's time they were.

 

Rear adjustment of drums....

Loosen the E brake, adjust the rear drums so that they just rub while spinning the rear wheels by hand. Pump the brake to center the shoes and check your adjustment again and adjust if necessary. When done, reset the E brake. The rear brakes, if not adjusted, use up a lot of pedal travel.

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Yes ive bled the rears, i have bled all 4 corners in proper order each time.

 

push rod has been adjusted

 

I just re bled the master, made sure the E brake didnt have tension, double checked the rear adjustment, and re bled all 4 corners again, and no cigar. Still plenty of fluid coming out.

 

After this session ive noticed that when bleeding the front calipers, when the bleeder valve is open the pedal only moves down  slightly 1/8-1/4 inch.

Im guessing im not sending enough fluid to the front then?

 

Ive heard several people do exactly this setup with just adjusting the push rod, so damn frustrating haha

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The push rod must be adjusted so that there is about 1/16" of play on the pedal. Just push down with thumb the pedal should move easily this amount before the push rod actually starts working. This just assures that the master returns to it's rest position and lets the pressure in the lines release back into the reservoir.

 

To test the vacuum booster.... Pump the brakes with the engine off to remove any residual vacuum. Push down on the brake pedal and hold. Start engine and observe that the pedal now drops slightly as the vacuum builds. This is normal operation.

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Ok pushrod is adjusted.

 

brake falls when i turn engine on, tho it doesn't fall very far because pressure doesn't build up that high in the travel

 

falls slowly as well.

 

still no brakes when cars on.

 

Should i be looking into a proportioning valve? 

do i have the wrong year zx calipers?

 

i even tried the MC off my 280z and it worked worse.

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The pedal drops slightly as the engine vacuum increases and helps you apply the brakes. This is why it's also called a brake booster.

 

All '79-'83zx calipers are the same even the turbo models.

 

 

Are the calipers on the correct sides? with the bleeder screws to the top?

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Yes bleeder screws are on top.

 

I shouldn’t have to go to a 15/16 bmc right?

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I have a 15/16" zx master with my Maxima calipers... which are a 6 cylinder car based on the Zcar platform. They work very well with a booster.

 

I'm surprised there are no brakes at all. Even a 7/8 would push enough fluid to work them. The pedal will travel farther to make up for the smaller size and it might feel slightly mushy but it would work. Some say that a slightly smaller master makes it easier to modulate braking pressure at near lock up when racing.

 

If you tried a 280z master and worse I guess we should assume that the masters work and aren't the cause.

 

 

 

Rear adjustment of drums....

Loosen the E brake, adjust the rear drums so that they just rub while spinning the rear wheels by hand. Pump the brake to center the shoes and check your adjustment again and adjust if necessary. When done, reset the E brake. The rear brakes, if not adjusted, use up a lot of pedal travel.

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I agreee I think it’s something to do with these calipers.

 

I’m getting plenty of fluid at each corner which is confusing.

I can see the caliper piston pushing on the pads and holding them enough to not move by hand. But at soon as engines on, nothing.

 

I’ve adjusted the rear drums enough to where if I give em another turn they lock up.

 

Maybe I’ll throw on the 3/4 bmc for the hell of it

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Ive checked now to make sure the push rod has adequate throw into the the master and it does. 

Initial push rod length is still good.

 

still looks like things are pointing to the calipers or proportioning valve.

 

When bleeding the rears, open bleeder valve and pedal goes to the floor.

When bleeding the front,  open bleeder valve pedal moves about a 1/8 -1/4 of an inch.

I've also noticed that the stream when bleeding the rears seems stronger than the fronts

 

 

Is this due to not enough fluid making it to the front via prop valve? 

and the brake light coming on when i slam on the brakes would indicate fronts are not getting enough fluid correct?

 

Ive also disconnected a caliper and didn't see much, to any fluid leaking out of the hard or soft lines.

not like the original brakes where it would be leaking like a sieve.

 

are there different prop valves for different year 610s??

 

 

 

 

I've also noticed that the stream when bleeding the rears seems stronger than the fronts

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I took a apart the booster to make sure that spacer was in place. Now it’s hissing and pushing are through the pushrod area.

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I'm not sure the 610 even has a proportioning valve. Brake bias is designed in by the master cylinder design and the size of the rear wheel cylinders, besides the fronts are unaffected by proportioning valves, only the backs are.

 

When swapping the master cylinder did the front and rear brake lines get swapped? The front of the master cylinder is for the rear brakes and the back of the master is for the fronts. If swapped by accident you would be sending more brake to the rears.

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I think there is a prop valve. Lines run from master into the box with the brake light switch to a prop valve and then to calipers/wheel cyl

 

No mix up, the lines are running to the correct sides. Should I try bypassing the what I’m. Assuming is that prop valve. I’ll take some pictures of everything when I get home.

 

Also with the master off, is some air coming from the pushrod in the booster normal? Or should I coat the pushrod in vasaline to seal it or something

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Only thing in the booster will be vacuum or normal air pressure. Maybe sound of air leaking in. Pump the brakes gently several times and if it goes away this is it.

 

 

Everything points to trapped air or the calipers are seized.

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Ok I’ll double check th booster for that.

 

I haven’t seen any air coming out of the calipers, I’ve bled them like 4 times now. Fluid seems strong enough.

I can see the pistons pushing on the pads as well. Idk something’s gotta be up these calipers

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mine did the same thing with all 610 brake parts air gets trapped in places i literally bled my brakes for 3 days before i finally got a petal if i were you i would go buy a vacuum bleeder it will help a lot 

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For how many times I’ve bled brakes I should have bought one forever ago haha. Thanks for the input

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I even put on the original calipers and master cyl and it still acting the same. Somethings off

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Could be air trapped in the metering blocks

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Try opening the bleeders on the front calipers... then bleed the rears. Having the fronts open will increase the stroke inside the master, pushing more fluid in the rear circuit. Then do the fronts.

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Alright, havent touched this hunk of junk for a few months now.

 

My plan was to start from the beginning with all original stuff, master, calipers, ect.

Make sure that all worked fine first.

But for the life of me i cant find my original 3/4 BMC

 

Getting back into it ive noticed this as well.

 

The new ZX calipers on the car seem different than an original seized set i have.

Hence why i have flipped the brake pads. The raised trapezoidal part of the pads i got didnt fit in correctly, but they did fit flipped with the trapezoid fitting into the piston fine.

Pads would have fit fine with these seized calipers.

]44059192411_83d6d55d09_b.jpg

 

Also appears to have different stampings.

I thought all ZX calipers were the same?

42250447980_9f2bb4d7d2_b.jpg

 

 

 

Also I probably asked this before but how am i to fit the bake shims onto these suckers?

Edited by MapleNuts

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The numbers are likely just mold or casting ID. Gotta figure there were likely dozens of molds for making these calipers fast enough and in quantity and more than one foundry involved. Likely also some slight revision was made during the run of the ZX '79-'83.

 

The anti rattle (squeal) shims? Probably they won't fit unless you get the thinner original factory pads. No worries, the brakes work exactly the same without them. If they squeal there are after market dressings that do the job as well. Additionally.... drive the car for 6 months and wear then down enough to slip them in but don't be surprised if they start to make noise.

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FINNALLY, brakes are working.Turns out you can’t trust “new” calipers as well. Took some old zx calipers and rebuilt them and now I have brakes!

 

Thanks again to everyone for the help!

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