300zx brake upgrade, extremely mushy brakes - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Imthel33test · 05-23-2008, 10:28 AM

Here's the story. I bought the car with front 300zx front brakes already on and they worked perfectly fine. Then the other day i had the rear 300zx brakes put on. On the front I didn't change anything but the front rotors and the front brake lines. In the rear, everything is new. New rotors, brake lines, pads, ebrake cables, ect. When I got the car back from the mechanic the brakes were realllllllllllllly mushy and they said they had bleed the brakes several time. So i suspected it was my master brake cylinder being too small. So I went and got a new 300zx master brake cylinder the BM44 which is a 1 inch. After removing the old master cylinder, I found out that it was a 15/16 meaning it was upgraded before from the 7/8 so i didn't think that the 1inch would be that big of an upgrade but I put it on anyways. In short, it didn't do anything. I had bench bled the master cylinder and bleed the entire brake system at least 7 times.

So the problem is that the brake pedal went almost to the floor and then started to catch but not really bite, or if you pump it, it would gain pressure and it would catch better. Again I have checked for leaks everywhere from the lines, to the bleeders to the master cylinder.

Then I changed the front pads. The same symptoms but the catch point is now about 1 or 2cm earlier and the pads really bite into the rotors. But the brakes are still mushy all the way to the floor until that biting point.

Sorry for the long story but PLEASE HELP! I have checked everything and asked several mechanics but none that have dealt with solely 300zx brake upgrades on a 240sx.

The car DOES HAVE ABS. I am not sure if that is at fault. So far from the forums, most people have done the upgrade without ABS, and if they had ABS they have only done the front brakes. I am not sure if that is the cause. Would I need a 300zx ABS actuator?

Any input would be very appreciated.

-Stacy

pbcstylez · 05-23-2008, 02:33 PM

how does your front calipers look like, bleeder valve up or down?

Imthel33test · 05-23-2008, 02:39 PM

I fixed the problems today. The rear calipers had the bleeders facing down.

Thanks everyone!

05-23-2008, 10:28 AM	#1
Imthel33test Zilvia Member Join Date: Feb 2007 Location: San Diego Age: 40 Posts: 224 Trader Rating: (4) Feedback Score: 4 reviews	300zx brake upgrade, extremely mushy brakes Here's the story. I bought the car with front 300zx front brakes already on and they worked perfectly fine. Then the other day i had the rear 300zx brakes put on. On the front I didn't change anything but the front rotors and the front brake lines. In the rear, everything is new. New rotors, brake lines, pads, ebrake cables, ect. When I got the car back from the mechanic the brakes were realllllllllllllly mushy and they said they had bleed the brakes several time. So i suspected it was my master brake cylinder being too small. So I went and got a new 300zx master brake cylinder the BM44 which is a 1 inch. After removing the old master cylinder, I found out that it was a 15/16 meaning it was upgraded before from the 7/8 so i didn't think that the 1inch would be that big of an upgrade but I put it on anyways. In short, it didn't do anything. I had bench bled the master cylinder and bleed the entire brake system at least 7 times. So the problem is that the brake pedal went almost to the floor and then started to catch but not really bite, or if you pump it, it would gain pressure and it would catch better. Again I have checked for leaks everywhere from the lines, to the bleeders to the master cylinder. Then I changed the front pads. The same symptoms but the catch point is now about 1 or 2cm earlier and the pads really bite into the rotors. But the brakes are still mushy all the way to the floor until that biting point. Sorry for the long story but PLEASE HELP! I have checked everything and asked several mechanics but none that have dealt with solely 300zx brake upgrades on a 240sx. The car DOES HAVE ABS. I am not sure if that is at fault. So far from the forums, most people have done the upgrade without ABS, and if they had ABS they have only done the front brakes. I am not sure if that is the cause. Would I need a 300zx ABS actuator? Any input would be very appreciated. -Stacy

05-23-2008, 02:33 PM	#2
pbcstylez Nissanaholic! Join Date: May 2005 Location: East Bay Age: 40 Posts: 2,110 Trader Rating: (0) Feedback Score: 0 reviews	how does your front calipers look like, bleeder valve up or down? __________________ parking lot pimpin... Seller Feedback here: http://www.zilvia.net/f/showthread.p...ight=pbcstylez

05-23-2008, 02:39 PM	#3
Imthel33test Zilvia Member Join Date: Feb 2007 Location: San Diego Age: 40 Posts: 224 Trader Rating: (4) Feedback Score: 4 reviews	I fixed the problems today. The rear calipers had the bleeders facing down. Thanks everyone!