Stan, <br> I was amazed at what a very small amout of run out would do. The front pistons are so large that it takes a lot of pedal strokes to move em very far. Happened to me on an old Ramcharger, almost pulled all my hair out before I got it cured

 

Wow, thanks for all the advice! I will pull the wheels off in a day or two and check the condition. I will shake the fronts down also to check the bearings. The master cyl is already installed, and like I said, it's a little better, and the brake light stays out now, but it's still a guess as to what kind of pedal travel to expect - alittle or a lot...<br><br>I'll let you all know.<br>

 

The weirdest one I ever encountered was a 67 or 68 Camaro that had been converted to disk brakes in the front. After turning a corner, or any sharp turn, you had no brakes until you pumped the pedal up. We finally found out that there was some kind of metal bumper on the lower control arm that pressed against the caliper when in a sharp turn, compressing the piston. This, of course, did not interfere with the drum brakes. I think we just cut that little piece off the control arm and fixed it.<br><br>Disclaimer: this cannot apply to this situation because the problem vehicle here was designed for disk brakes, unlike that Camaro.<br><br>Check out that bearing deal. Weird as it sounds, I can believe it.<br><br>Chris

 

The strange part was the brake thing just happened one day with about 2100lbs in the box. No warning, the truck drove and handled just fine (gyroscopic effect I think). The really annoying thing was that I had been taking the truck to the same shop for service for 2 years, and doing preventative maintainence (so I thought). Was skeptical when the shop called, but it fixed the problem . We had a chat about what was involved in a PM program.

 

So... what was the problem? ???

 

dma,<br><br> You said you changed the master cylinder. Did you change the plastic checkvalve on the master cylinder? How does the vacuum line look that comes off the pump that goes up to the checkvalve? <br><br> I was having the same symptoms.....intermittent. Well, really it was when I pumped the pedal too much, but it became more frequent. I remember seeing a post about it over on the TDR; maybe it was even a TSB. In fact, I seem to recall that there is an improved checkvalve.<br> The vacuum hose was weakening due to fuel/oil and collapsing. I changed out the checkvalve at the same time so I can't swear to which one was the culprit, but I haven't had the problem since. <br><br>Just a thought.

 

dma<br> you got brakes yet ??? let us know what the fix was

 

I have ran into this on several ocassions on different vehicles and it can be a number of things includeing the abs the most common cause is the master cylinder. What you need to do first is isolate the master cyl by plugging the ports that come out of it and then step on the pedal with the truck running and see if the master cyl is bleeding off. If not it is something else did you bleed your abs? When I got my truck the abs had air in it and it had a low sinking pedal. Matt