maybe 1990B150318's problem fix is a possibility?
Thanks 1990B150318 for the suggestion, btw

 

Was the master cylinder a new or rebuilt unit? It's possible you got a bad rebuild. I've gotten several in a row until they got to a different rebuild batch.

 

unknown, had it done in a shop...
Clamping off at the front flex lines, solves the fading issue...
Does this bring any idea's to mind?
Why this makes a difference I don't know...
Makes no sense to me...

 

Let us know after you bleed the combination valve. The hard lines should run from the master cylinder down to the combination valve which will have a bleeder on it like a caliper. Start there then then wheels.

But yeah I had the exact same issue you describe, perfectly. And, my fluid was leaking out of the cap. Like you I was like, "aw hell it's the booster" but I was just reading that if there was a leak at the booster it usually causes the engine to run like ****.

 

Yea, Thank's to everybody that's replied to my questions...
I will go through these steps bleeding the Proportioning Valve/combination valve and see if that fix's the problem.
If that don't work then maybe another MC...
I'll update this post when I am done...

Thank's again Folks.

 

If clamping the lines stops the fade, it isn't your master cylinder. Normally, when the flex lines fail, the brakes get rock hard or the caliper sticks in the brake position. Are the flex lines cracked on the outside? I have seen brakes be spongy with a bad line. I'll bet you either have a bad caliper or bad flex line.

 

The flex lines look good, no cracks and do not bulge or swell under pressure, nor do the brakes drag or pull to one side. the previous front pads were worn pretty evenly and the calipers pistons collapsed evenly and smoothly using a 6" C-clamp during the re-shoe.
This kind of stuff makes my head hurt...

Ghosts I tell ya, Ghosts..../lol

 

Try clamping off just one side, see if the problem is still present. If it is, then the other side is the issue. Exactly what that issue is though.... well, that's a good question.

 

we did clamp off the drivers side first and problem was still there, clamped the right side and problem was gone had a firm pedal with about 1" of travel and got no leak down...
going to have to do it again and be sure which side has the problem...
Thank You

 

If one is bad, I'd replace both of them. Just to be safe.