Brake Fluid Flush GMT800

[WFO]

The brake pedal on my 03 goes down just a little bit more than normal. Brakes work fine though, and master cylinder is still full, with the original fluid in it. Has 72k miles on it.

I'm about to flush it the old fashioned way with a helper, and I was wondering if I need to do anything different due to the ABS?

 

[Edelbrock]

I would try this:

Have someone start the engine and stomp hard on the brakes repeatedly while you check each rubber brake hose for bulging and replace any that are. Should be 3 hoses to check. Then I would bleed the brakes starting with the shortest brake line and ending with the longest brake line - so probably LF RF LR RR. Once this is done, the brake peddle should be back to normal.

If there is a bulging hose, then replacing the fluid wont help anything.

If there is no air in the system, then replacing all of the fluid might introduce air, compounding the problem - making it harder to isolate.


Brake fluid wont compress, regardless of its age.

 

[fast 99]

If the excessive travel developed with a full master here are a few possibilities. Am sure there are others. Rear shoes out of adjustment if drum brakes, as suggested swelling brake hose, bad master, loose front wheel bearings causing pad retraction, tight wheel cylinder or caliper. I would do a complete inspection and if nothing found flush fluid being very careful not to run it out.

As an alternate get a turkey baster suck the fluid out of master and refill. Won't be as good as a flush but better than doing nothing.

 

[Grit dog]

^What he said.
I’ve become a big fan of the lazy man’s fluid flush on brakes and power steering. And sometimes differentials if no drain plug and no real reason to open up the differential cover.
If you run the numbers and don’t mind “wasting” fluid at the expense of ease and time, you’ll find that usually 3-5 lazy man flushes gets mostly all new fluid in the system.
I lucked out on both squares as they both had extensive work done to them and very fresh brake fluid. On those I do a single suck and refill bout once a year.
The 77 had a leaky steering return hose so it got self flushed over the first few months. Went thru a couple quarts refilling occasionally. It was the one original component on the new engine the PO had installed in it.
But for the OP, if they’re a little spongy, likely have to figure out the cause which could be bleeding them so may as well do a real flush.
But think about it, the lazy man’s flush is about as good. Most brake calipers have the line coming in the top and the bleeder on top. So not really draining the fluid behind the cylinder completely just during a couple bleed ing sequences.
lazy man’s way allows the old and new fluid to mix for a while (I usually drive for a few weeks or longer between brake refills)