installed 300zx MC and 300zx brakes and the car stops like crap

[koukiKA240]

last night after work i finally installed my z32 mc just in time to drive down for the twi night autoX. The autoX i was at 2 weeks ago i competed with the z32 brakes and 240sx mc and complained that the pedal was unpredictable and squishy, so i upgraded. The event last night the brakes felt AWFUL, the scariest part was i couldnt get the car to stop in the stop box, i couldnt MAKE it lock up. the pedal feel was good but the brakes were 100% unresponsive. I had a TON more stopping power with the 240sx mc than with the 300zx one but sacrificed pedal feel and consistancy.

This cant be normal. I filled the mc and allowed the car to gravity bleed for about 10 mins and then bled it with my bleeder bottle and a 1 2 3 hold bleeding method. I saw no air in the lines and then headed for the track.

what could be the problem? Is it possible to upgrade to the z32 brake booster?thanks,~Sam

[BaliLover]

front and rear Z32 brakes or just front?

[nismofly]

did you bleed all 4 corners or just the fronts?

[koukiKA240]

only fronts, and blead all 4 corners, from RR to LR to RF then LF.~Sam

[Dano]

sounds like you still have air in the system, either that or the primary cup seal of the primary piston may be leaking (that's the seal that holds pressure, and generally the first thing to let go within the mc) ...

-Dan

[koukiKA240]

the mc is brand new, so i hope that is not the issue. If that winds up being it i will be irate.~Sam

[SmithSR]

Did you bench bleed the MC before install?Normally people don't ask but I didn't see you mention this.

[koukiKA240]

the day before install i pushed some fluid through it testing a flare we made to see if it would hold pressure, and fluid remained in the mc. But i did not purposefully bench bleed it.~Sam

[eddiec]

do you have abs? if so that could need bleeding to.

[koukiKA240]

no abs

[Dano]

my roommate had a very similar problem when we put bigger brakes on his car. I took the m/c off and bench bled it properly, problem solved. I'd bench bleed it, but make sure to bleed the whole system afterwards.

-Dan

[koukiKA240]

i found time to bleed the brakes properly at every corner fora bit yesterday and the problem has gotten better. so i am going to bleed them once a day untill the problem goes awaythanks for ur help guys.~Sam

[Dano]

i would bet on air being trapped in the m/c.

-Dan

[llamabeta]

only fronts, and blead all 4 corners, from RR to LR to RF then LF.~Sam

Guys please note he mentioned he *only* had the Z32 brakes up front. (Good question bailover) I dont recall seeing any info anywhere that states that Z32 MC works well with *only* the fronts.

[koukiKA240]

"One of the questions that always comes up is the proportioning of the 300ZX MC vs the 240's MC and the effect of using the 300ZX MC with stock 240 rear brakes. Below are a few excerpts from FreshAlloy members:

The way OE proportioning valves work is that the front and rear line pressures go up by the same amount until the pressure reaches the so-called "split point". At this point, the rear pressure increases at a lower rate than the front pressure (with the proportionality factor given by the reducing ratio).

Now the reducing ratio for the Z32 and 240sx MC's are the same (0.4), so the only difference is the split point. The Z32's split point is lower than the 240sx, so above the split point, the Z32's rear line pressure will always be lower than that of the 240sx.

What this is saying, is that there is no way the rear brakes are going to lock up first by swapping in a 300ZX MC while using Z32 front brakes and stock 240 brakes in the rear."~Importnut.net

~Sam

[BaliLover]

So doesn't that mean, that the pressure required to make the split is lower, and at the same time, once it makes that split, the pressure to the rear brakes is lower?

It won't cause the rear brakes to lock up, but could this also mean it doesn't allow them enough stopping force and making the front brakes work harder?

Are you possibly losing fluid? Were the Z32 calipers new or used?

I think you may have had a problem previously, and switching to the Z32 MC increased the problem. I know the Z32 MC is not a direct (out of the box) bolt on, and it requires a little modification to work. Did you install the flare fitting into the new MC? If not, this would for sure cause a line pressure problem and make the brakes feel crappy.

FWIW, I'm running stock rear, Z32 fronts, stock MC/Booster, and I don't have any complaints about pedal feel or with them being "unpredictable." I find its just as easy to modulate them as before, but I can now lock them up whenever I want to.

[koukiKA240]

I suppose it could have been a pre-existing problem but what the hell could it be? Hydrolic brakes just are not that complicated.

The brakes were used, but a nissan rebuild kit and 8 new pistons make em brand spankin new.

I put a bubble flare on the line, i hacked open 2 240sx, mc. One was a made on fitting, therefore could not be removed. The other one was too large, and would not fit in the hole. The hole it came out of was considerably larger than the one in my new mc. Actually come to think of it...

Could the fact that i dont have the normal fitting pressed in the mc cause this issue? The hole was larger, the fitting has a smaller hole to match the holes on the 2 front brake lines. ... But it wouldnt be more pressure but more volume... so would that affect my braking. Since the fluid is, well a fluid would it be sending more of the braking force the the rear? Is this making any sense im more or less typing out loud....

****, it makes sense... doesnt it??????~Sam

[dumbstroke8]

when you bleed the brakes, you should tap the calipers with a dead-blow hammer a few times, because sometimes air bubbles can be stuck and need somep persuasion to get out.

[smokey240sx]

I came across this article on zilvia.net that might help.http://www.zilvia.net/faqs/arc...r.asp