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1997 Nissan Pathfinder Brake Bleed

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In my 97 Pathfinder with 198k miles I recently changed the front passenger caliper and the brake blaster as that went bad (I adjusted rod as should be).

Is it possible to bleed the current master cylinder along the same way as I bleed at the wheels? Basically having someone press down on the pedal and crack the lines to the master. I bled each point on the Pathfinder using the two person method and the order the FSM states, starting with the LSV, and about 10 times each spot until no bubbles seen in the bottle hose. The brakes are much better but I still observe that I have to give it a pump to harden up more and get rid of that sponginess. Calipers are all new, so are rear cylinders, and hoses are fine.

I will admit the master has run dry once after a brake line broke a few years back, but after changing the line, refilling, and bleeding, I did not really notice any issues. When I fill the reservoir I with brake fluid I notice bubbles or air lock occasionally that will make the brake fluid take some time to go down. The pedal holds firm pressure when the engine is off and you pump the pedal hard so I’m sure the master is not losing any pressure internally.

I saw in one of Scotty’s video he even changed a master cylinder without bleeding at wheels. Since I bleed the whole system thoroughly yesterday, can I just crack the two lines and bleed at the master two person method without introducing air into system? 

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Posted by: @ars1218

It’s not a new master cylinder, it’s the one currently on the vehicle. I suspect air is inside, but I was wondering if I can just bleed that on the vehicle without having to redo the whole system.

Since air bubbles might potentially travel from the master cylinder to any other point in your brake system I would bleed the whole thing. It might require a bidirectional scan tool to bleed the ABS if so equipped, especially if air gets into the ABS module.

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I always found it beneficial to bench bleed the master cylinder before installation.  Then right rear, left rear, right front, left front.   

It’s not a new master cylinder, it’s the one currently on the vehicle. I suspect air is inside, but I was wondering if I can just bleed that on the vehicle without having to redo the whole system.

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No.  Any time any part of the closed, hydraulic system is opened, the whole system needs to be evacuated of air as correctly recommended by @chucktobias.

Is it possible for a master cylinder to be bad despite holding firm pressure when engine is off? I am going to change the hoses on the brake system (the rear to the diff and driver side was changed a few months ago, only the passenger side was left) as well as change out that passenger caliper with another new one just to see because Ive bled it and the pedal is still very spongy and gets firm when pumping.

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You must bleed the whole system.  No shortcuts.

I did. After master I did the LSV, left rear wheel, right rear, left front, right front. That’s according to FSM. Still have same problem which started after brake booster and right caliper replacement. Push rod is adjusted correctly.

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The correct sequence is -

right rear - left rear - right front - left front

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