# 92 pathfinder se 4wd. rear brakes do not work.



## blindguardian (Mar 18, 2013)

I have replaced the master cylinder, brake hoses, rear rotors and brake pads. I bench bled the master cylinder and bled it while it was installed. The brake lines are perfect. The brake light is on and the anti-lock brakes light is on, my dad drove it to work a few days ago (before replacing the master cylinder) and the rear brakes locked up on him. Yesterday we installed the new master cylinder hoping it would fix the problem. The rear brakes still do not work. I think its the ABS or load sensing valve, but I have no idea what to do about it. I need this vehicle to drive back and forth to work, but i don't want the brakes locking up on me. And I would like to fix all the major issues before I start driving it. If someone could help I would greatly appreciate it. My dad is a mechanic but he has never done anything with ABS or load sensing valves. So we don't know where to start.


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## IanH (Feb 11, 2003)

If ABS light is on can you get a code read on a 92?

Anyway the ABS isnt working so you have to diagnose the issue. 
My guess is the ABS sensor at rear, mine is 3 channel and i guess yours is to. So there should be one rear sensor somewhere.

I think the load sensing valve adjusts the rear brake pressure like a proportioning valve, even if its messed up the ABS should still work to stop it locking up.

Hope this helps.


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## IanH (Feb 11, 2003)

Thinking about it any sensor or ABS failure will disable the ABS, so you will have to look at the whole system.


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## smj999smj (Jan 1, 2006)

WD21's only have rear ABS; the sensor is located at the front of the rear diff. There is an actuator (looks like a proportioning valve with an electric harness) mounted to the right frame rail under the vehicle and the rear ABS control module mounted under the center of the dash. There is also a 6-pin check connector near the driver's kickpanel. It's a simple system and there is a preliminary check and self-diagnostic procedure in the service manual. If you don't have one, you can get one here if you e-mail the site owner for a password. WHile they don't have one for a 92 Pathy, they do have a listing for a 95 Pathy, which should be very similar if not the same:

Nissan and Infiniti Service Manuals

The LSV (load sensing valve) is a proportioning valve of sorts. It's used to regulate the rear brake fluid to the rear wheels based on the change in clearance between the body and the rear axle, where it's mounted. In simpler terms, if the back of the vehicle is loaded heavy, it will cause the back end to "squat." Without LSV, this would change the braking characteristics of the vehicle. The LSV helps compensate for that. Because of that, it's adjustment is critical. If a vehicle is left stock, it usually never needs any adjustment. However, if modifications are made to the suspension or a body lift kit installed, the LSV adjustment would need to be addressed. On their own, they normally are pretty reliable and you don't see many problems with them unless the get badly rusted or the spring breaks. 

When there is an issue that affects the mechanical braking system, it will also cause the ABS light to illuminate. An electrical issue could also cause this. Some important questions:
-Did this issue exists before the master cylinder, pads and rotors were replaced?
-Did you bleed the entire brake system and do so in the correct order (listed in the service manual): 1) LSV (2) left rear (3) right rear (4) left front (5) right front?
-Have you checked the parking brake cable to make sure that it is not too tight?
-Have you jacked up the rear of the vehicle and tried turning the rear wheels by hand (in neutral) while somebody presses and releases the brake pedal, to make sure it's engaging and releasing properly and not staying "locked" or "dragging?"


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## blindguardian (Mar 18, 2013)

The whole reason I replaced everything is to get the rear brakes to work, we followed all the correct procedures. And the person I bought it from had taken out the E-brake. The proportioning valve is good because it is in the master cylinder, which I replaced. I have a manual. The only thing I can think of is the acuator is not letting fluid get to the rear calipers.......my dad is just going to take it to a shop and have them try to figure it out. I don't know what to do. I' love this car so I'm willing to put money into it. The reason why the person took out the E-brake is because the vehicles rear brakes kept locking up. I think it was stupid to take that out but what can I do....i have exhausted everything I know so far. Anymore help will be appreciated.


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## IanH (Feb 11, 2003)

OK. is the brake circuit split front to back ?

If the rear brakes lock, and the springs are OK, nothing mechanical back there AND it is split front to back check the master cylinder Actuator rod is fully back, IE the pedal is adjusted correctly.

What do you mean rear brakes don't work ?
They never work and you can turn the rear wheels with the pedal depressed ? IE as above ??


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## blindguardian (Mar 18, 2013)

Yes I can hold the brake and the rear wheels will still move. There is no hydraulic pressure back there when hitting the brake. But the front brakes work just fine. I asked my dad about the master cylinder rod and he said he will try to take a look at it tomorrow.


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## IanH (Feb 11, 2003)

What happens when you bleed the rear brakes ?


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## blindguardian (Mar 18, 2013)

Fluid comes out of the bleeder screws like it should, so fluid is going back there. I don't understand why the brakes won't work.


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## IanH (Feb 11, 2003)

it has to be the LSV ? try disconnecting and connecting a connector in its place to confirm, this should be cheap.

The locking up I suspect is a separate problem, and for me the master cylinder adjustment is the main suspect. As the fluid warms it cant expand into the reservoir and put on the brakes. I cant explain why the brakes then work when they don't normally. so this may be wrong.


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## blindguardian (Mar 18, 2013)

The lsv is in the master cylinder, so that was replaced with the new one. I am lost as to why this car does what it does. I took to a show today so hopefully they can figure out what I couldn't. Thank you for all your help, I really appreciate it.


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## IanH (Feb 11, 2003)

No, the LSV is by the rear axle. It adjust the brake pressure with load.

Yes the prop valve is in the master cylinder.


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## blindguardian (Mar 18, 2013)

Well, my dad said that it does not have an lsv. And after looking in the manual, I found that to be true. So I don't think that is the problem.


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## smj999smj (Jan 1, 2006)

Any chance the rear calipers are faulty?


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## blindguardian (Mar 18, 2013)

We checked those, the work just fine.


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## IanH (Feb 11, 2003)

So the only thing between the master cylinder and the rear brake is the rear ABS unit !!


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## smj999smj (Jan 1, 2006)

To my knowledge, since you don't have LSV, there shouldn't be anything between the master cylinder and the rear brakes other than the metal lines, the hoses and the ABS actuator.


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## rogoman (Dec 16, 2004)

blindguardian said:


> I have replaced the master cylinder, brake hoses, rear rotors and brake pads. I bench bled the master cylinder and bled it while it was installed. The brake lines are perfect. The brake light is on and the anti-lock brakes light is on, my dad drove it to work a few days ago (before replacing the master cylinder) and the rear brakes locked up on him. Yesterday we installed the new master cylinder hoping it would fix the problem. The rear brakes still do not work. I think its the ABS or load sensing valve, but I have no idea what to do about it. I need this vehicle to drive back and forth to work, but i don't want the brakes locking up on me. And I would like to fix all the major issues before I start driving it. If someone could help I would greatly appreciate it. My dad is a mechanic but he has never done anything with ABS or load sensing valves. So we don't know where to start.





blindguardian said:


> Yes I can hold the brake and the rear wheels will still move. There is no hydraulic pressure back there when hitting the brake. But the front brakes work just fine. I asked my dad about the master cylinder rod and he said he will try to take a look at it tomorrow.


Your two different posts are contradictory. One says the rear brakes are locking up. The other post says there is no hydraulic pressure at the rear brakes when the brake pedal is depressed. Which is it then?


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## IanH (Feb 11, 2003)

couldnt that be due to a bad ABS unit


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## smj999smj (Jan 1, 2006)

Mechanical failure of the ABS actuator is possible. They are generally pretty reliable, especially on the R-ABS systems (I've never seen one or heard of one failing in all the years I worked for Nissan.), but anything's possible!


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