300zx brake problem on a s13 help!

[johnny butt]

Upgrading to a Z23 MC is NOT required. If the one you have is bad then go ahead and get one since you need a replacement anyway.

The brakes are vaccuum operated via the booster, are you sure you don't have a vaccuum leak or faulty booster?

not required, but it's 50$ for something that saving your life is dependent upon.

seriously...you spent at least 300$ to throw some new front brakes on, is 50$ more too much to save your life?

really, 50$ > your life?

anyways...

Here are my calipers.I haven't quite figured out how to mount them so I can have the bleed holes on the top side. They basically look like the same-side calipers....



calipers in same position just flipped around so NISSAN is visible.



not quite sure how I should mount them / I.E. which one is driver, which is passenger...

[94_240sx]

not quite sure how I should mount them / I.E. which one is driver, which is passenger...

Sorry to say this, but both of them are for the passenger side.

For the OP, I have s13 BMC in good condition. Let me know if you want to buy it. I did the swap recently and this is it. It's in perfect working condition. No leaks at all.

[nevertheless]

dont fuuck around, get the z32 BMC.

[ddgsxr504]

not required, but it's 50$ for something that saving your life is dependent upon.

seriously...you spent at least 300$ to throw some new front brakes on, is 50$ more too much to save your life?

really, 50$ > your life?

How will a Z32 BMC save your life. Since you are so insightful tell me why you NEED to get one? All it really does is improve pedal feel, it has nothing to do with braking bias or modulation. If you swap to the Z32 rears also then yes I would highly suggest getting the Z32 BMC. You can use the stock S13/S14 BMC with no issues, the only difference is it will be easier to lock the front brakes up, so I guess that means you just need to get better at brake modulation with your feet.

[94_240sx]

not required, but it's 50$ for something that saving your life is dependent upon.

seriously...you spent at least 300$ to throw some new front brakes on, is 50$ more too much to save your life?

really, 50$ > your life?

I think what he meant was get a new (any) BMC and fix it ASAP since it's a critical part on the car.

[duffman1278]

^^No he said to get a Z32 BMC earlier.

However OP, I had a somewhat similar issue and I bled each caliper in the proper order of course about 5 times when I did it and it was STILL not braking properly. I got lucky though and was able to get my hands on a compressed air self bleeder. It wasn't until I let the compressor suck all the air out of the brakes that my brakes finally went back to normal.

You're just going to have to bleed the hell out of them.

[i240sx]

automatic 240 come will a different BMC and it is good for front z32 and 240 rear conversion only....i heard due to the auto transmission being heavier the BMC was built for more weight which give you a better pedal feel so there is no need for a z32 BMC unless you have a 5sp or full z32 brake conversion...

[ddgsxr504]

^^No he said to get a Z32 BMC earlier.

However OP, I had a somewhat similar issue and I bled each caliper in the proper order of course about 5 times when I did it and it was STILL not braking properly. I got lucky though and was able to get my hands on a compressed air self bleeder. It wasn't until I let the compressor suck all the air out of the brakes that my brakes finally went back to normal.

You're just going to have to bleed the hell out of them.

I agree, I bought a Craftsman vaccuum pump to bleed brakes. Best $100 I ever spent and makes 1 man brake bleeding a breeze.

[johnny butt]

^^No he said to get a Z32 BMC earlier.

because you're already going to get a new BMC in the first place, why not get the z32 since they are the same price?

Sorry to say this, but both of them are for the passenger side.

is this going to give me any problem when I try to put them on? Or will the drivers side just be a little harder to bleed?

[Hijacker]

It is definitely the MC. The reason is that your MC was already on its way out. Now that you've effectively increased the surface area of the calipers' pistons, the MC has a lot of backpressure on it. This in turn allowed fluid to seep past already worn MC piston seals. This also tends to be an issue in the colder months as the seals constrict, and it's easier for the hydraulics to start to leak.

The reason your friends' works fine is that his MC wasn't as worn as yours. I recommend replacing your MC with a Z32 MC (whether it is a 1" or 16/15"). The reasons are due to over pressurization of the hydraulic system. The smaller diameter S13 MC exerts too much force on the surface area of the pistons of the Z32 calipers. It's designed to push on 2 pistons of X diameter, not 4 pistons of Y diameter.

I used an S13 cylinder for 2 years on my Z brakes, and locked the brakes up too often. Once I switched over to a Z MC, the braking system felt more balanced, and I no longer locked my brakes up, allowing for quicker stopping times (and I don't plow into road cones in auto cross due to locked brakes anymore).

The diameter of the master cylinder determines both how much brake force you'll get for a given pedal effort, and how much pedal movement there will be. The stock 7/8-inch master cylinder has a piston area of 0.60 square inches, so 100 pounds of force shoving on the piston from the combined effort of your foot, the pedal lever ratio and the brake booster, will make 167 psi (100 lb/0.60 in2) of fluid pressure with which to squeeze the calipers. Moving to a 1-inch master cylinder gets you 0.79 square inches, which makes only 127 psi from the same 100 pounds of footwork.

Since we had complained that the brakes felt touchy and overboosted, this reduction in pressure would be exactly what we needed. We also complained that there was too much pedal movement. The bigger master cylinder helps here, too. A 7/8-inch cylinder moving 0.1 inches pumps .060 cubic inches of fluid to the brakes. A 1-inch cylinder would pump .079 cubic inches. That means it would take less pedal movement to move the brake pads the fraction of an inch from their resting position to the rotors.

Here's a bit from an old article Dave Coleman wrote. It should help put things in perspective.

[johnny butt]

The reason your friends' works fine is that his MC wasn't as worn as yours. I recommend replacing your MC with a Z32 MC (whether it is a 1" or 16/15"). The reasons are due to over pressurization of the hydraulic system. The smaller diameter S13 MC exerts too much force on the surface area of the pistons of the Z32 calipers. It's designed to push on 2 pistons of X diameter, not 4 pistons of Y diameter..

your S13 master cylinder isn't designed for four pistons per caliper.

Thanks, chances are they'll believe you before they believe me.

Either way,I've known I had two of the same Z calipers for a while (didn't think anything of it), I'm just somewhat worried I won't be able to mount or bleed them properly, and i've already got them powdercoated and ready to toss on..It's gonna be a ***** trying to find just one 30mm drivers side and have to rebuild & powdercoat it...

sorry for the threadjack.

[Bumnah]

I have not read the entire post so I may be saying something others have already covered.

01. Make sure the bleeder on the calipers is pointing up. If the bleeder is on the bottom you are not getting the air out. Mount it upside down if need to be to get the bleeder on top. Bleed the system, remount the caliper back upside down like normal after the bleeding is done. I'd just get the proper caliper.

02. With oem rear brakes and Z32 front brakes the s13 bmc is fine. You need the z32 bmc if you have front and rear z32 brakes

03. Obviously test your MC to see if it's working. It's been stated. Pump the brakes hard with the car off. Hold it, the pedal should stay stiff, if it sink. MC is bad. Replace it. I'd go with the z32 BMC then for sure, because if you ever upgrade the rear the bmc is there.

04. If you replace a BMC; IT MUST BE BENCH BLED. BENCH BLEED IT! Not bench bleeding can cause damage to the BB as well. Put the BMC on wet, as in, bench bled! Easy to do, and there is a cheap bench bleed setup some guy on here posted. It works perfectly well.

[johnny butt]

I have not read the entire post so I may be saying something others have already covered.

01. Make sure the bleeder on the calipers is pointing up. If the bleeder is on the bottom you are not getting the air out. Mount it upside down if need to be to get the bleeder on top. Bleed the system, remount the caliper back upside down like normal after the bleeding is done. I'd just get the proper caliper.

nice, thanks, that's what I was thinking, but it's not in my options / time constraint / budget to try and source a single 30mm 300zx caliper.

[Hijacker]

02. With oem rear brakes and Z32 front brakes the s13 bmc is fine. You need the z32 bmc if you have front and rear z32 brakes

I disagree with this. I had overboosting issues with my original setup of S13 rear brakes and MC paired with the Z32 26mm front brakes. The pedal was way too sensitive, and the system locked up too often for me to consider it a safe way to set things up. Also, rear brakes do less than 10% of the braking of the car, so I would rather have my front brakes proportioned correctly and my rear brakes see less applied pressure than have my fronts receive too much pressure and my rears be proportioned correctly.

[Bumnah]

I've driven 300zx front brakes with oem rear brakes and oem bmc. No issues. I've only seen issues with 300zx brakes front and rear, with oem bmc. Dunno what to tell you, do what works for you I guess.

Advance Auto can source aluminum 30 mm calipers for you. Tell them you own a 92 300zx. they come rebuilt. You'd just need to paint them or powder coat them or whatever.

Easiest way of mounting the brake caliper upside down is to flip it. So instead of face the front bumper the caliper is sitting closer to the doors. I just put something under neath the caliper to hold it. I then used elastic straps to hold it onto the rotor. that way it doesn't fall, and you use the rotor to keep the pistons from falling out. Be easy loosening and tightening; don't want to strip anything.

[Flip240sx]

ok i replaced the bmc and didnt fix the problem i think i got some messed up calipers thats what im thinking cuz like i said b4 everythin was working fine b4 the swap ..somebody told me that the pistons on the calipers are pushing out but not returning (leaking internally) is this true ?? so what im gonna do is get em rebuild..

[Bumnah]

Advance Auto can source aluminum 30 mm calipers for you. Tell them you own a 92 300zx. they come rebuilt. You'd just need to paint them or powder coat them or whatever.

[dlydrvn240]

take them off and take off the dust boot and see if there is any fluid visible or squeeking out of there. You can also try the ole gravity bleed for a day or two with the car sitting level and all your bleeders open...then close them all and bleed as you normally would.

It really sounds like air in the lines man, could be the calipers...but really think its a bleeding issue.

As far as a rebuild kit you can go to PDM and get a rebuild kit...its pretty easy. Hardest part is getting the pistons out...which if you have access to an air compressor is not that difficult either.

[tamdo714]

i didnt see anywhere that you had converesion lines. maybe thats your problem.

[Flip240sx]

okay so i got me another pair of z32 calipers damn pep boys only had the cast iron so i got em freshly rebuild i slapped em on and was bleed em and was for sure now my brakes would work but no but the braking greatly improved i only pump it once and it stops but still goes all the way to the floor is going on man im really getting frustrated... changed the bmc and got fresh calipers i ran out ideas of what could the problem be???ima re bleed em again tommorow so the aluminum calipers that i replaced were good ugh what a pain in the butt

[Flip240sx]

ok never mind the braking didnt im prove. it did but only while the car is moving at 3mph i test drove at 35 mph all i hear when i pump the brake pedal is air after 4 pumps the calipers do their work so th last thing i could think of is the brake booster ima go get one tommorow at my local junk yard good luck to me..

[Flip240sx]

so all that work i went trought did nothing i changed the booster today and bleed the system again and the same thing is happening i dont get it what im out ideas tired and feel like put my stock calipers backs why is this happening is not rocket science it shoulda work the first time

[94_240sx]

Remove the wheels and check calipers. I'm suspecting bad calipers or bleeders.

[nissans13240sx]

Make sure all your bleeders are on top of the caliper and not the bottom.

[Bumnah]

List car specs. Brake changes made and a detailed explanation of what is happening.

[Flip240sx]

i got onther pair of rebuild calipers..

[Flip240sx]

the bleeders are on top

[Flip240sx]

92 SE first i had the aluminum 30mm then i bought the cast iron rebuild when i thought the other pair were bad im using stock 300zx lines and yes i checked them for leaks and bleeders are on top also replaced bmc and chaged my brake booster today ..so whats happening here is that i hold the pedal turn the car on and the pedal goes to the floor i let go and pump it again the prussure comes back keep pumping it and its normal now i move the car just abit 5mph again floor repump peldal gets hard... now 20 to 30 mph 3 pumps pedal goes to the floor 4th pump get hard again ...after all the things i replaced its the same thing nothing chaged well it feel way better with the rebuild caliper but still the same thats all there is to ..also i checked the vacuum line to the booster and its fine ..what you guys think about this ???

[hungryjoseph]

tell us how you're bleeding them, maybe you're doing something wrong, and also, are you losing any fluid in the resevoir?

[94_240sx]

tell us how you're bleeding them, maybe you're doing something wrong, and also, are you losing any fluid in the resevoir?

Good point. I'm sure you did it right, but did you do like this?

http://www.youtube.com/watch?v=Hf1iPbeg778