I have a 98 2500 2WD 5.9 gas 8800GVW with 244k miles with a master cylinder shaving tiny metal flakes out of the bore to the point that the brake fluid looked like metalflake paint when I last flushed it

The fix is obvious enough, but my question is whether anyone else ever had this happen and if it took anything other than a new master cylinder and a lot of flushing to clear it out of the brake system.

That’s all easy enough to do but I’m wondering if that’s good enough to clear the proportioning valve and ABS unit (rear only. It seems everything is working properly other than maybe setting off the ABS a little too often under low speed (city traffic) hard braking when empty, which sometimes makes me wonder about the state of the proportioning valve, though of course it might have to do with the Centric fleet/severe duty/tow truck brake shoes (now that they have broken in) and new drums I installed to go with the Centric premium drilled discs and powerstop Z36 truck and tow pads I installed up front. It doesn’t much pedal pressure to stop or slow it down.

I will be replacing both front calipers and front hoses along with the master cylinder since one caliper piston was binding up along with it’s bleeder valve port being completely blocked.

so the questions:
would having the brakes pressure flushed by a shop be necessary or worth the expense? I could likely accomplish same by installing a tire fill valve thru a hole drilled in the old mc cap.

Has anyone had same problem, if so, what did you do as far as a flush?

Any input Re proportioning valve or ABS hardware?
thanks in advance for your input.

 

What I did was flush each wheel with the old bottle trick. Then went out and made the ABS activate a few times then redid it. I noticed on the second flush some old fluid came out of the abs unit

 

The RWAL ABS unit is just a dump valve. So, should be too bad to get it cleared out. I might be tempted to reverse flush the system a bit, and see what comes out.