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Hello all!

So the brake pedal in the tracker will slowly fall to the floor when stopped at a light or stop sign etc., classic symptoms of a bad master cylinder. I replaced the master cylinder and thoroughly bled the entire system per the Chilton manual for a RWAL system. By the way, all 1991 Geo trackers come with an RWAL system.

Upon spending numerous hours scouring the Internet for information on RWAL systems, I found a Wagner brake help sheet. In this sheet it says that you will experience the same symptoms if the dump valve (within the pressure limit (isolation/dump) valve) is stuck open due to foreign matter keeping it open. I have already tested the wiring harness leads on the PLV and all check out for the proper resistance as listed. There is a bleeder valve near the accumulation section of the PLV. Does anyone know if this is a bleeder valve for the accumulation section? Is it a bleeder valve for the chambers that are utilized during non-ABS situations? Nonetheless I went ahead and bled it which did not correct the situation.

The next test is to remove the rear brake line from the master cylinder and install a plug. If the pedal no longer falls to the floor, then it is safe to say that the dump valve is the culprit. If the problem persists, then it is a faulty master cylinder. My mechanic friend is going to do this test tomorrow, but I thought I would go ahead and get started with this thread to document the progress, get help, and hopefully help others.

Thinking ahead, I thought I'd gather some opinions regarding bypassing the RWAL if the PLV (no where to be found for purchase at any price) is found to be at fault.

A few things I already know:
1) The RWAL system is a standalone system meaning that it has its own control unit so disabling it should not affect any of the other ECU functions.
2) The RWAL is disabled when the Tracker is in four-wheel-drive mode.

I am thinking of fabricating a brake line that will connect the rear outlet port in the master cylinder to the two-way joint, thereby physically diverting the brake fluid and bypassing the PLV. Then I figure if I trick the RWAL control unit into thinking that the tracker is in four-wheel-drive mode, the brake indicator light should function just fine, and BOOM! problem solved. Does anyone have a wiring diagram for the RWAL electrical circuit which shows the relationship between the control unit and the four-wheel-drive indication and/or sensor circuit? Or does anyone think it would be easier to just disconnect the RWAL electrical components? And if so will all the other brake light operations continue to work normally?

Looking forward to a good discussion here!! Thanks!!
 

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Let's see. First, the FSM indicates that some cars may have LSPV instead of RWAL. And I would first have looked for leaks (loss of pressure) in the brake lines, checked to see if the master cylinder is losing fluid (it can leak internally).
And I would dump the Chilton's, and get a proper FSM, as Chilton's is full of misinformation (as is Haynes). Normally, if there is a problem with the RWAL, the EBCM will throw a code. And I would say that just because it is possible for the dump valve to open and decrease brake fluid pressure it doesn't necessarily mean that this is what is happening to your car. Normally, this would throw a code 9 from the EBCM - presumably your brake light works with key on and goes off once the car starts??
Personally, I would do some diagnostic testing on my brake system, rather than just getting rid of part of it. As the front discs work off of hydraulics, too, there are plenty of places to look. ;)
 

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The front and rear brake systems are hydraulically independent of each other, are they not? Therefore IF the rear section is malfunctioning as you suspect, then the brake PEDAL would still maintain some distance from the floor, while operating the front brakes, correct?

I think you have a Master cylinder issue still. ;)
 

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Hmmm....I disconnected my rear brakes for a couple of days while waiting to fix them, and found that with just the front brakes working, the pedal was extremely hard, with very little downward movement.
I still wonder at the level of the brake fluid in the MC - any loss? Have you thoroughly checked the entire brake system for leaks? If none, the MC can leak internally, causing fluid loss.
There are two different circuits in the MC - one for the front and one for the rear brakes.
 

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Discussion Starter #5
I put a re-manufactured master cylinder in it, and it still did the same thing with the pedal. So I bought a "new" one, and the same exact problem still exists... Hard to imagine that I got two "bunk" master cylinders from the parts store. A total of three master cylinders have been used (if you count the original), and still the same problem. There is no fluid loss either.
 

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And I would dump the Chilton's, and get a proper FSM, as Chilton's is full of misinformation (as is Haynes).
Good advice. I just downloaded one from a link I found here in the forums:
SUZUKI MANUAL

presumably your brake light works with key on and goes off once the car starts??
Yes.

Normally, if there is a problem with the RWAL, the EBCM will throw a code. And I would say that just because it is possible for the dump valve to open and decrease brake fluid pressure it doesn't necessarily mean that this is what is happening to your car. Normally, this would throw a code 9 from the EBCM
Would I get a code 9 if there was foreign material keeping the dump valve from seating in the closed position properly?
 

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The dump valve/solenoid is in the pressure limiting valve under the master cylinder, all of which can (and should) be bled to make sure that there is no air in the system. The dump solenoid also works off of voltage, info of which is in post #8 here:
http://www.suzuki-forums.com/suzuki...993-91-tracker-4x4-driveline-binding-2wd.html
So you may want to check the wiring, before deciding to replace this valve (or do away with the RWAL).
When your brake pedal sinks, aside from being soft and spongy which is a different issue, it is basically that it is losing hydraulic pressure somewhere, either internally or externally. Did you buy a new master cylinder, or a rebuilt/Chinese knock-off?
 

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Just a thought here. When you say you completely bled the system after installing the new master cylinder, did you bench bleed the master cylinder before installation? If not you probably still have air in the system. A slow dropping pedal is a sure sign of either a leak or air in the system.
 

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The dump solenoid also works off of voltage, info of which is in post #8 here:
http://www.suzuki-forums.com/suzuki-...nding-2wd.html
I had actually read that post last week before joining :) and in my first post I stated that everything measured properly ;) "I have already tested the wiring harness leads on the PLV and all check out for the proper resistance as listed."

Did you buy a new master cylinder, or a rebuilt/Chinese knock-off?
"I put a re-manufactured master cylinder in it, and it still did the same thing with the pedal. So I bought a "new" one, and the same exact problem still exists..."

did you bench bleed the master cylinder before installation?
Yes.
 

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I had the transmission rebuilt last month and it developed a pan leak so I sent it back on warranty to be fixed. When it arrives, I am going to isolate the the front circuit from the rear rear circuit by plugging the rear outlet on the master cylinder. If the pedal doesn't sink, then I am certain that the dump valve is stuck open.

I'm thinking about it this way: If the dump valve is open at all times, fluid will be forced against the accumulator piston, which will collapse the accumulator piston spring. As the accumulator reservoir begins to fill up, it would make sense that the pedal would begin to drop to the floor, yes? When pressure on the pedal is released, the accumulator piston spring forces the fluid back into the system. Anyone aboard on this hypothesis?

A couple things I haven't really mentioned: When I press on the pedal, the brakes work and feel just fine, not spongy, no excessive travel, stops fine, etc. But when I have to sit at a light, it slowly falls to the floor. If i pump the pedal, the whole process starts over, it slowly falls to the floor. The second thing I've noticed, is couple times when I've come up to a stop sign rather fast and have braked a little hard side (in no way hard enough for the RWALS to kick in) the front brakes make a noise like the caliper pads are pinching the heck out of the disks. Not a squeak or a grinding noise, but somewhere in between. Basically it is a sound which, after all this research, has led me to believe that the rear brakes aren't engaging 100% and are thereby not helping the fronts very much, causing them to take the brunt of the stopping force.
 

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I am going to isolate the the front circuit from the rear rear circuit by plugging the rear outlet on the master cylinder. If the pedal doesn't sink, then I am certain that the dump valve is stuck open.
The front and rear hydraulics work off of different lines. Frankly, with the rears blocked off, the brake pedal will be extremely hard, normally, and, if the pedal doesn't sink, only indicates that the problem is in the rear, but not what or where.
You can check the dump and isolation valves in the pressure limit valve, with a DVM. The dump valve is normally closed and should have no voltage going to it on the white/green wire. The brake computer provides 12v through this wire, when it opens the valve.
 

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It's best to start your own thread, advising of your symptoms and what testing you have done to try to determine your problem.....;)
 
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