1994 Suburban brake system flush

Alright I got a 1994 Suburban 4wd with a 5.7L and the brake fluid is really dirty. It's really dark brown. How would I go about flushing the entire system? I'm also about to change the master cylinder too because the fluid seems to be bypassing it. Could I flush it with the master cylinder acting up like that or would I need to change it then flush it? Thanks in advance.

 

Change first, then flush. Be sure to bench bleed the new master before installation. For bleeding, here's one way:

Start at furthest wheel from master. Break bleeder screw loose and install a long bleeder hose (any small hose will do as long as it is snug fit on the nipple) on the bleeder. Put loose end in a glass jar with a small amount of clean fluid in it. Now open the bleeder and slowly depress the brake pedal to the floor and let it back up. Leave the bleeder open throughout. Wait a few seconds after the pump and release and then repeat. Continue until you can see clear fluid being pumped out. Close bleeder and proceed to next wheel until all four are done. CAUTION: Monitor fluid level in master reservoir and keep it topped off. When all fours wheels have been flushed go back and do a "normal" brake bleed of pumping pressure with bleeders closed, opening bleeder, and closing it when the pedal reaches the floor board. Be prepared to be shocked at what the fluid looks like that comes out.

 

Well on the last comment... as for the bleeding process.. why not bleed for air on the first try... bassically as your having someone press on the brake.. pump until clean comes out.. then have someone press and hold... open the bleeder valve for a moment and re close as they are pressing the pedal and closing the vavle before thier foot hits the floor.. then move to next wheel.. save you sime time and easier

 

My humble opinion: Over 18 years of wrenching, I used every type of pressure, suckula (vacuum), hose & jar, and helper methods of bleeding known to man. The one that I used almost exclusively for 10 years, and the only one that never failed me: gravity. No useless contraptions required, no helpers required, and no sequences to worry about. The only vehicles this will not work on are the abs systems that use pump motor/accumulator, which I believe are almost non-existent anymore.

Simply remove the master cyl. lid(s), fill it up, and open all 4 bleeders at the wheels. You do have to make sure the vehicle is as level as possible. Then walk away and do something more important. Check the fluid level every 10-15 minutes until you have clean fluid coming out of all wheels. Close the bleeders, install the lid(s) on the master, pump up the pedal, then re-open the bleeders one at a time to "burp" them. You may have to repeat the "burping" process once or twice.

 

Yep, that'll work, too. As to my method, yes you can also do the bleed on the last pump or two. Last time I had to do one my assistant (aka spousal unit) wasn't immediately available so I got all the flushing done first and when she was able to help we did a quick bleed.

 

To do the slow, gravity, open all bleeders at the same time, do you have to pin the brake pedal to the floor?? Have the engine ignition on at all??

Tried bleeding the brakes with the spousal unit, ONCE, my eight-year old girl is sooo much more helpful!!. And she doesn't ask worthless questions! And she wants me to teach her about cars!

Seriously, I finally flushed out my system, beginning at rear right and now this old car stops very well!

 

Were you shocked at what the old stuff looked like?

Negative on brake pedal and ignition.

 

20 years doing this junk/ when u go 2 replace the master c undo all brake lines and just spray some brake cleaner or carb cleaner[same thing ]and just flush um out let it sit 4 a hour or so it can evaperate hook your lines back n bleed it. do unhook lines at the caliper/cleaner might mess with the rubber so just telln ya how 2 get the lines clean realy cant clean the calpers eazyer 2 replace um.

 

geno...are you saying spray brake cleaner or carb cleaner into the brake lines??

Whoa....first I ever heard of that...

 

Brake cleaner would probably be safe - it's almost pure alcohol and evaporates quickly. Carb cleaner on the other hand, is NOT the same thing, and would be a VERY bad idea.