Brake System Problem

[BoostGetsULaid]

So I'm not the best with brakes. Well i was about to go 180sx brakes but in the middle of it i decided not to and put my stock on. While i tried to bleed my brakes and i still couldn't get the air bubble out.

I had over 5 different people help me out and still couldn't get it out. I got a One-Man Brake Bleeder kit and still couldn't get it out. When the car is off i can get about 75% of pressure and when i keep pumping when the car is off it goes to full pressure and when i take a break it goes back to 75% pressure.

After this i thought that would be good enough to drive. But then when i turned my car on the brake pedal loses all pressure and i have to pump to get it back up and again when i take a break the pedal loses pressure but when i lose pressure when the car is on it loses all pressure.

When I pump the pedal with the car on the RPM's slowly go up. and when i stop they go down.

I was told by the people that were helping me that it was the master cylinder. But on i did some searching that the RPM thing would be the brake booster.

Any suggestions?

[180fan]

test the booster first. with the car off, press your brake pedal. if the pedal height gets higher to the point where you can't press it down any, then your booster is fine.

More likely your master cylinder though. You've bled the brakes for days and still the mush. Probably the master.

How exactly are you bleeding the brakes though?

[BoostGetsULaid]

Thanks for the help man. my car as been inactive for a month now.

Well when i have people help me bleed. We'd first top off the reservor and leave the cap off. Then we'd remove that rubber thing on top of the bleeder valve and plug a clear tube on the top of it. then after that someone would pump the brake pedal till they built pressure up (usually like 10 times) then hold the pedal down while another releases and quickly closes the valve. we'd do this till all the air bubbles stopped goign through the tube and do afew more to make sure. we'd add more fluid after that.

We'd go:Driver FrontDriver RearPassenger RearPassenger Front

And when i used bleeder vaccum thing i'd top the fluid off and leave the cap off. pull the rubber thing. attach the hose to the valve, pump afew. then go and pump the brake. then release the valve and pump the vaccum while the valve was open then when no more air was getting vaccumed through i'd close the valve. then repeat the same way.

[BoostGetsULaid]

i just tested the brake booster. i went out there and my car is totally off. pumped the brake it kept getting harder but not to the point where i can no longer push but it was some what hard

[sephiroth99]

usually to bleed brakes it is from the farthest to the nearest i.e. pass. reardriver rearpass. frontdriver front

[dlhS13]

I would go with the master cylinder. Sounds like the booters fine. Had same problem but they really just didn't work at all. Swapped the brakes and master cylinder all z32 stuff. Fixed the problem but it really not a fix for your unless you want a whole new project. Sorry not really being able to help that much.

[BoostGetsULaid]

yeah thanks i didnt really want to go out and buy like a brake booster install it and then have it not be the problem ya know i knew it was one of the 2.

[dlhS13]

I know what you mean. Its like the water pump and radiator problem. If you really don't know then you go though the hassel of putting a new water pump. Then find out that you really should have bought a radiator. Speaking from exsperience. Anyways good luck.

[BoostGetsULaid]

if i install it and it comes out to be wrong im coming after all you! jk lol

[dlhS13]

I'll come to you. Winter time, I want to get out to Whistler this year you got it made up there.Lucky

[leper421]

Check the slider pins on the calipers, make sure they move freely and arent seized. Floating calipers like the 240 has are reliant on free moving slider pins.

I never had this problem with my 240, as I always did things the right way However, a friend of mine with an 87 300zx didnt listen to my advice. He was having brake problems. His brakes were spongy and very unresponsive. It turned out he never greased the slider pins when changing his brakes, and one of them seized.

ALWAYS CHECK AND RE-GREASE YOUR SLIDER PINS WHEN CHANGING YOUR BRAKES!!

[BoostGetsULaid]

i dont even know what hte slider pin is

[leper421]

This is in reference to the front brakes. The rear is similar.http://www.scriptsandwich.com/...s.jpg

When you change your front brakes you loosen two 14mm bolts and remove the lower one completely in order to swing the caliper up. What those two 14mm bolts screw into are the slider pins. They have rubber boots between them and the torque member. Those pins should slide freely into and out of the torque member. The "torque member" as Nissan calls it, is the bracket that bolts to the steering knuckle, that holds the brake pads, and that the caliper bolts to.

[BoostGetsULaid]

oh i know what your talking about now.... what should i use to grease them?

[leper421]

oh i know what your talking about now.... what should i use to grease them?

Um... grease

but seriously, use high temp grease, and make sure they move freely everytime you change your brakes. Floating calipers depend on these pins moving freely.

[BoostGetsULaid]

yeha i know grease but i was wondering if there was one better than another or a certain brand you like

[BoostGetsULaid]

so i replaced the master cylinder with a new one. bench bleed it and installed it. i used one of thsoes vaccum bleeding kits and bleed all 4 brakes.

Passenger rear. Driver rear. Passenger front. Driver Front.

Twice and then i got in and pumped like there was no tomorrow the pedel barely moved it was extremely stiff and when i pumped i'd only move it slightly. Then when i turn the car on when i pumped the pedel the RPMs didnt go up like last time. but i still had no pressure. i had the car on and had my sister pump and i could feel the caliper moving just alittle cause the pad is already on the rotor already which leaves no rooms for compression. i checked the slider pins and there seems to still have grease in them

My Theories

1: I bench bleed wrong2. Didnt bleed it right3. Need to grease the slider pin4. Brake Booster is bad.

[BoostGetsULaid]

bump

[leper421]

Heres a bunch of images taken from the factory service manual. Follow the steps in the order they appear in the images, and check EVERYTHING it says to check. If you dont want to remove the master cylinder, skip over the "output rod length" check, but if everything else seems ok then go back and check it. The images are for a 93, but I just checked the part numbers and everything is the same for 89-93.

http://www.scriptsandwich.com/...s.zip

If all checks out ok (or before you do the above) also check the following:Remove each caliper from the wheel, one at a time. Put a block of wood between the piston and the other end of the caliper. Have someone slowly press the brake pedal and verify that the piston moves. I'm not sure, but a 2x4 might be too thin, you want something with a thickness that will allow the piston to extend 1/4"-1/2".

And, I hope you know that using a C-clamp to push in the piston destroys the rear calipers...

so i replaced the master cylinder with a new one. bench bleed it and installed it. i used one of thsoes vaccum bleeding kits and bleed all 4 brakes.

Passenger rear. Driver rear. Passenger front. Driver Front.

Twice and then i got in and pumped like there was no tomorrow the pedel barely moved it was extremely stiff and when i pumped i'd only move it slightly. Then when i turn the car on when i pumped the pedel the RPMs didnt go up like last time. but i still had no pressure. i had the car on and had my sister pump and i could feel the caliper moving just alittle cause the pad is already on the rotor already which leaves no rooms for compression. i checked the slider pins and there seems to still have grease in them

My Theories

1: I bench bleed wrong2. Didnt bleed it right3. Need to grease the slider pin4. Brake Booster is bad.