I've got a 1992 Dodge diesel 4wd. I found that the master cylinder reservoir for the rear brakes ran dry. I've bled the brake lines at each wheel after watching several Youtube videos on how to do that (I had never bled brakes before).. Some of the videos seem to say I still need to bleed the master cylinder and the combination valve if the reservoir ran dry. My Dodge manual says nothing about bleeding the master cylinder and combination valve. It seems to me if I've bled the brake lines at each wheel, then that should automatically mean the master cylinder and combination valve have been bled, and I don't have to separately bleed them.
Can someone clue me in on the answer?
Thanks.

 

How does the brake pedal feel? Where did the fluid go that WAS in there? You have/had a leak somewhere. Need to find and fix that first. (if you haven't) I only bleed the master cylinder if I am replacing it, or, I find there is air in the system I can't get out otherwise.

 

After bleeding the brakes I've looked for evidence of a leak. No leak, and the reservoir is, so far, staying full. Wierd. As for the feel of the brakes, I don't like the feel - it still seems spongy and I find I'm wondering if the power assist is working. It seems to call for a fair amount of leg muscle.

 

Probably still have air in the system somewhere.

 

have you checked to make sure your rear brakes adjusted and where did the brake fluid go? dealt with something similar on my friends 91w250 a couple months ago. wheel cylinder failed destroying the new 3" shoes that were installed only a couple years prior. did you make sure to bleed the right rear first? also when possible i generally like to let gravity do most of the work. leave the bleeder open till you start getting fluid out of it. i would recommend doing it this way. you need the line to go up so the air can travel up but the line can stay filled with fluid.