No More Spongy Brake Pedal - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

240 2NR · 07-02-2003, 10:24 PM

Wow!!!!

Ok so I had orignally posted a thread about the brake issues I was dealing with after installing a new MC. Turns out after writing a long *** post my dial up connection at work disconnected and my post was lost.

BEST LUCK EVER!!!!! Turns out that since I didn't have responses from you guys I actually went and read the instructions that came in the box and came across the exact issues I was having. I've installed a MC before but the install was a big improvement right out of the box so I didn't read on and my friend who was working on it with me didn't bother to explain how to trouble shoot problems that didn't exist.

To back up, since I bought the car my pedal has been firm, but with a long stroke before engagement, though the brake lights turn on within a few mm so I knew it wasn't the pedal free play. I changed the stock pads to KVR's which made a big difference when hot and improved fade resistance, but cold it was just as bad. I've bled the lines numorous times without a noticable change and the MC seemed like the last option besides SS lines. I had read the FSM about checking the brake booster, but the procedure requires compressed air so I ignored it.

So this weekend I changed the MC and while I felt like my braking force was improved (there was definitely some leaking past the seal), modulation was worse than ever, accompanied by a groaning noise. This wasn't going to do with a 1000 mile road trip ahead of me.

So I read the little instruction manual and right there was the procedure for curing just that series of problems.

Turns out the piston for the brake booster wasn't seating in the MC piston in the retracted position and now with the new MC the problem was worse. Pedal travel before engagement was long, even though the pedal was firm once the pistons engaged.

So an hour later, super stiff pedal with very short travel!!!!!

Here's how to do it. It should only take about an hour and really only requires a 12mm wrench, a 7mm wrench and a pair of needle nose locking pliers (non locking will work, but locking is much easier).

-Unbolt the two nuts securing the MC to the brake booster.

-Pull back the MC to reveal the BB piston

-There is a round piston with a 7mm fitting on a threaded pushrod

-The entire pusrod/ piston assembly freely rotates by itself so you will have to use the locking pliers to hold the pushrod (easier if the pushrod is deployed so have a friend press on the brake pedal or rig up a way to have the pedal depressed while you work on it, I used a jackstand and a pair of 20+mm wrenches)and the 7mm wrench to turn the piston counterclockwise (or clockwise if you have brake dragging to retract the piston). I used 1.5 full turns and it went from very spongey accompanied by a groaning noise to super firm (almost too much) while allowing the wheels to turn without dragging the brakes. My guess is if you are not getting a groaning noise with the brake pedal depressed at idle you should go less than a full turn.

Then just rebolt the MC and go for a test drive (you may want to check for brake drag by lifting a corner and spinning the wheel while it's off the ground).

Pic....

240 2NR · 07-03-2003, 08:04 AM

Well I thought this would have generated a bigger buzz.

I thought I would add that in the picture it looks like the MC is completely removed from the brake booster. If you just loosen the two nuts, there's enough flex in the hard lines that you can pull the MC away from the BB 2-3 inches, which is tight to work with, but just enough, without having to remove any lines and then bleed everything and then find out it needs to be a adjusted again (my worry before starting). I just unclipped the first two clips on the firewall and gained an extra inch or so, which was enough to work with. A shop light will help tremendously (as will not driving the car for an hour prior to trying this so the exhaust manifold just inches away is blazing hot while you work,

). Seriously, I always thaought there was more involved in adjusting this, but it was very easy and should be a lot more clear once the MC is loose and you can see the piston I'm talking about. If it still looks too hard for ya, just tighten down the two nuts on the MC and you're right back where you started.

If I knew about this 2 years ago it would have been the first thing I did on my car.

240 2NR · 07-03-2003, 08:18 AM

FREE Free free free freefreefreefreefree!

timmybgood · 07-03-2003, 10:30 AM

perhaps this is why some people with Z32 brakes have some mush? excellent write up btw

240 2NR · 07-03-2003, 10:45 AM

Could be, but my brakes are stock. I think the Z brakes has more to do with the volume of fluid being moved (more travel once engaged), this just seats the piston to begin with which eliminates the travel prior to engagement so its firm right away instead of having .5" of travel or so before actually getting some resistance. I seiously think I have less than .5" of travel total now. It rocks!

I was all set to order some stainless lines, but I guess this cures most of the issues, though I'll probably still get them.

Warwick5s · 07-03-2003, 10:47 AM

kick ***!

i'll try this tomorrow morning. my pedal seems to move about 3" before it does anything.

**West** · 07-03-2003, 11:32 AM

Thanks!, ill have to do this when I put my 5lug and Z brakes on.

MorganS13 · 07-03-2003, 02:24 PM

i'm gonna have to try this.. it'll be my lazy way of making up for my "dirty brake fluid" according to the dealer.

Hubie · 07-03-2003, 02:29 PM

OMG!! This is exactly what I need. Mine doesn't make a groan noise though. I'm try this tonight. If I f up somehow, then I can drive my parents car. They're out of town and I'm house sitting...hehehe. Thanks.

hurleyboi514 · 07-06-2003, 04:13 PM

awesome, now i dont have to buy a Z brake master cylinder. its very stiff now and ive got Z brakes!! good job man!

240 2NR · 08-08-2003, 11:34 AM

Had to dial back my setting by a quarter turn since I was having issues with my brakes dragging. It wasn't a huge deal and was just enough to keep my KVR's nice and warm all the time but once they got hot (during some spirted mountain driving) I could feel them noticably dragging as their friction coeffient increased. It also took a long time to cool them back down.

Took it back a quarter turn, which seems like it might have been a touch too much. Apparently this adjustment is very sensitive. The brakes no longer drag and the pedal response is better than it had previously been, however it's still a bit softer than ideal. Maybe an 1/8 turn back will be just right.

**mrmephistopheles** · 08-08-2003, 10:15 PM

.....and into the archives we go!!

07-03-2003, 08:04 AM	#2
240 2NR Zilvia FREAK! Join Date: Dec 2001 Location: Denver Posts: 1,131 Trader Rating: (0) Feedback Score: 0 reviews	Huh, no replies? Well I thought this would have generated a bigger buzz. I thought I would add that in the picture it looks like the MC is completely removed from the brake booster. If you just loosen the two nuts, there's enough flex in the hard lines that you can pull the MC away from the BB 2-3 inches, which is tight to work with, but just enough, without having to remove any lines and then bleed everything and then find out it needs to be a adjusted again (my worry before starting). I just unclipped the first two clips on the firewall and gained an extra inch or so, which was enough to work with. A shop light will help tremendously (as will not driving the car for an hour prior to trying this so the exhaust manifold just inches away is blazing hot while you work, ). Seriously, I always thaought there was more involved in adjusting this, but it was very easy and should be a lot more clear once the MC is loose and you can see the piston I'm talking about. If it still looks too hard for ya, just tighten down the two nuts on the MC and you're right back where you started. If I knew about this 2 years ago it would have been the first thing I did on my car. __________________ Steve 93 240sx FB currently very clean and for sale

07-03-2003, 08:18 AM	#3
240 2NR Zilvia FREAK! Join Date: Dec 2001 Location: Denver Posts: 1,131 Trader Rating: (0) Feedback Score: 0 reviews	OH yeah, I should have said in the topic heading, IT'S FREE!!!! FREE Free free free freefreefreefreefree! __________________ Steve 93 240sx FB currently very clean and for sale

07-03-2003, 10:30 AM	#4
timmybgood Zilvia Member Join Date: Mar 2003 Location: central ohio Age: 37 Posts: 229 Trader Rating: (0) Feedback Score: 0 reviews	perhaps this is why some people with Z32 brakes have some mush? excellent write up btw __________________ 1995 SE

07-03-2003, 10:45 AM	#5
240 2NR Zilvia FREAK! Join Date: Dec 2001 Location: Denver Posts: 1,131 Trader Rating: (0) Feedback Score: 0 reviews	Could be, but my brakes are stock. I think the Z brakes has more to do with the volume of fluid being moved (more travel once engaged), this just seats the piston to begin with which eliminates the travel prior to engagement so its firm right away instead of having .5" of travel or so before actually getting some resistance. I seiously think I have less than .5" of travel total now. It rocks! I was all set to order some stainless lines, but I guess this cures most of the issues, though I'll probably still get them. __________________ Steve 93 240sx FB currently very clean and for sale

07-03-2003, 11:32 AM	#7
West OMNOMNOMNOM Join Date: Dec 2000 Location: Denver, CO Age: 40 Posts: 6,456 Trader Rating: (0) Rides Gallery: West Feedback Score: 0 reviews	Thanks!, ill have to do this when I put my 5lug and Z brakes on. __________________ West - Zilvia.net - Toyobaru.net - NapkinSketch.com

07-03-2003, 10:47 AM	#6
Warwick5s Zilvia Junkie Join Date: Sep 2002 Location: Madison, WI Age: 39 Posts: 504 Trader Rating: (0) Feedback Score: 0 reviews	kick ***! i'll try this tomorrow morning. my pedal seems to move about 3" before it does anything.

07-03-2003, 02:24 PM	#8
MorganS13 Zilvia Addict Join Date: Dec 2001 Location: Midwest Posts: 707 Trader Rating: (1) Feedback Score: 1 reviews	i'm gonna have to try this.. it'll be my lazy way of making up for my "dirty brake fluid" according to the dealer.

07-03-2003, 02:29 PM	#9
Hubie Leaky Injector Join Date: Aug 2002 Location: TX Age: 40 Posts: 124 Trader Rating: (0) Feedback Score: 0 reviews	OMG!! This is exactly what I need. Mine doesn't make a groan noise though. I'm try this tonight. If I f up somehow, then I can drive my parents car. They're out of town and I'm house sitting...hehehe. Thanks.

07-06-2003, 04:13 PM	#10
hurleyboi514 Zilvia Addict Join Date: Mar 2002 Location: The Fort Posts: 905 Trader Rating: (0) Feedback Score: 0 reviews	awesome, now i dont have to buy a Z brake master cylinder. its very stiff now and ive got Z brakes!! good job man! __________________ HighTach Motorsports

08-08-2003, 11:34 AM	#11
240 2NR Zilvia FREAK! Join Date: Dec 2001 Location: Denver Posts: 1,131 Trader Rating: (0) Feedback Score: 0 reviews	Had to dial back my setting by a quarter turn since I was having issues with my brakes dragging. It wasn't a huge deal and was just enough to keep my KVR's nice and warm all the time but once they got hot (during some spirted mountain driving) I could feel them noticably dragging as their friction coeffient increased. It also took a long time to cool them back down. Took it back a quarter turn, which seems like it might have been a touch too much. Apparently this adjustment is very sensitive. The brakes no longer drag and the pedal response is better than it had previously been, however it's still a bit softer than ideal. Maybe an 1/8 turn back will be just right. __________________ Steve 93 240sx FB currently very clean and for sale

08-08-2003, 10:15 PM	#12
mrmephistopheles Inactive Admin Join Date: Mar 2002 Location: BFE Age: 19 Posts: 14,334 Trader Rating: (9) Rides Gallery: mrmephistopheles Feedback Score: 9 reviews	.....and into the archives we go!!

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