R50 rear brakes not getting any pressure.

[TheRadBaron]

I'm at one of those stages in life where all of my vehicles break at the same time. I ran into something odd on my the 1999 Pathfinder that I just bought today. I didn't have time to look into it further than I did this evening so it might be something obvious, but I thought that I'd take a few minutes and ask here first in case it was a known problem. My truck has rear drums.

When I bought the truck I noticed that the brakes were acting strangely. In my experience they felt like maybe the rears weren't working. I had my wife help me look at them today and this is what I found. I had her pump the pedal and I cracked the rear, driver side bleeder valve. Fluid came out, pedal went down, just like normal. We did this another time or two and then no more fluid came out when the valve was opened. The pedal didn't go down, either. I moved to the passenger side rear and nothing came out there, either. Pedal didn't go down. It was like the valves weren't even opening.

So then I moved to the rear load-sensing proportioning valve. I had her pump the pedal and I cracked the bleeder on the prop valve. Fluid came out, pedal went down. After that, same story of no fluid and no pedal movement.

At this point I had to call it a night and I didn't look into it any further. Any ideas what could cause the rear brakes to not get any pressure? I know that it could be a number of things but I thought that it was worthwhile to ask here and see if anyone has had a similar experience. I'm an old hand at working on brakes but I'm pretty new to ABS and load-sensing prop valves.

Thanks.

[hawairish]

So the pedal won't even compress a little bit? Does it seem like a hard/mechanical stop? With the truck off, the ABS shouldn't be a factor, and I don't think even a mal-adjusted LSV would lock the line either. Seems a bit puzzling indeed...

 

 

[TheRadBaron]

No, it's not that the pedal doesn't go down at all. In fact, it goes down more than it should. The front brakes are operating but the rears aren't. It's just that when the pedal is pushed down and any of the bleeder valves in the rear brakes are opened, the pedal doesn't go down any further like it normally would.

It's probably just a bad master cylinder. I have a new one on the way that should be here today. I'll report back with my findings. Thanks.