# Brake problem



## max556 (Jan 15, 2005)

I have a weird brake problem that I can't figure out.
2000 Maxima, V6, ABS
When I step on the brake pedal, it goes down half way just like if the master 
cylinder had an internal leak, the rest of the travel is normal.
I replaced the master cylinder, no change.
I plugged both outputs of the master cylinder and the pedal had no travel.
Then I plugged the front port and connected the rear port to the brakes,the pedal felt normal.
Then I plugged the rear port and connected the front. Now the pedal started bleading down half way.
Obviously something on the circuit that handles the right front and left rear
wheels has an internal leak that affects the pedal.
The components in question are calipers, ABS motor, proportioning valve.
Any ideas? Please help. This car is driving me nuts.
Thanks.


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## Matt93SE (Sep 17, 2003)

proportioning valve is internal to the master cylinder I believe. may be separate on these guys, but I've forgotten now.

have you bled the system properly? sounds to me like you've simply got an air bubble in the line somewhere. did you boil the brake fluid somehow?

try re bleeding the system first and see where that gets you.
after that, I would try capping each brake line at the caliper (similar to what you did with the master cyl) and see where that gets you.


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## max556 (Jan 15, 2005)

Matt93SE said:


> proportioning valve is internal to the master cylinder I believe. may be separate on these guys, but I've forgotten now.
> 
> have you bled the system properly? sounds to me like you've simply got an air bubble in the line somewhere. did you boil the brake fluid somehow?
> 
> ...


I pulled the master cylinder and started from scratch.
I held it on the vice horizontally and bled it until I was satisfied.
Installed it and bled the connections before tightening the lines and then
I used a vacuum pump (I previously used the standard manual method).
The pedal is the best I've seen so far, still not where it should be.
During the last bleeding (one of many), The two front calipers bled dirty dark fluid. That's strange considering how many times I had already bled them.
I think the ABS was holding fluid somewhere.


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## rps180 (Aug 20, 2005)

It does take awhile to properly flush thru the entire brake system even with a power flushing system. Takes the machine a good 10~15 minutes of continuous flushing with all four calipers done at once. You may still have air in the line considering that dirty fluid still came out the last time you bled the system.


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## [email protected] (Sep 5, 2005)

Brake hoses will cause this also. There are hard to diagnose but you can pull the wheels have someone push the pedal down and inspect the lines for bulging.



max556 said:


> I pulled the master cylinder and started from scratch.
> I held it on the vice horizontally and bled it until I was satisfied.
> Installed it and bled the connections before tightening the lines and then
> I used a vacuum pump (I previously used the standard manual method).
> ...


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## max556 (Jan 15, 2005)

rps180 said:


> It does take awhile to properly flush thru the entire brake system even with a power flushing system. Takes the machine a good 10~15 minutes of continuous flushing with all four calipers done at once. You may still have air in the line considering that dirty fluid still came out the last time you bled the system.


I am looking to buy a pressure bleed tool.
Something inexpensive that I can use for the family cars.
Thanks.


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## max556 (Jan 15, 2005)

[email protected] said:


> Brake hoses will cause this also. There are hard to diagnose but you can pull the wheels have someone push the pedal down and inspect the lines for bulging.


You are right, the hoses looked good.
Thanks.


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## metro273 (Sep 16, 2005)

You might have sticking slide pins on the calipers, front or rear. Also, your rear caliper pistons might be seized.


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