2004 Suburban Z71 brake issue

[03GMCYukonXL]

Ok so I have brand spanking new calipers, rotors, and pads all the way around but I still barely have brakes. No lines are broken. When the ignition is off, the pedal will sink almost to the floor. I've bled them like 5 times and no air bubbles comes out.

I'm wondering if it's the brake booster. I do not have the hydro brakes. I have a regular brake booster with the vacuum assist canister. Could the vacuum assist be bad? I'm not that familiar with brakes. I just want this thing back on the road. Is there a way to test the vacuum assist?

 

[afpj]

Bear with me because we don't know what you know... How many miles on the master cylinder? How did you bleed the brakes? Did you use a pressure Bleeder at the master cylinder reservoir or a vacuum bleeder at each corner? Did you use the two-person method and if so, was the brake pedal pushed all the way to the floor? Lots of stories of old master cylinders crapping out after a bleed because the pedal was pushed beyond its normal travel and the seals completely fubarred from that. Did you use a bi-directional scan tool to bleed the ABS?

 

[03GMCYukonXL]

Bear with me because we don't know what you know... How many miles on the master cylinder? How did you bleed the brakes? Did you use a pressure Bleeder at the master cylinder reservoir or a vacuum bleeder at each corner? Did you use the two-person method and if so, was the brake pedal pushed all the way to the floor? Lots of stories of old master cylinders crapping out after a bleed because the pedal was pushed beyond its normal travel and the seals completely fubarred from that. Did you use a bi-directional scan tool to bleed the ABS?

225,000 miles on the master as far as I know and I used the 2 person method and they pushed them all the way down also as far as I know. I used no other bleeding or flushing method

 

[Scottydoggs]

have to ask. are the bleeders facing up. aka at the top of the calipers? its super easy to mix em up and put em on the wrong side., down side is they will never bleed any air out.

if your booster was bad you'd have a rock hard pedal. like when the engine is off, pump the brakes the pedal becomes rock hard and super hard to push.

bad master would sink to the floor with ease. unless you got a load of air trapped in the system.

 

[03GMCYukonXL]

have to ask. are the bleeders facing up. aka at the top of the calipers? its super easy to mix em up and put em on the wrong side., down side is they will never bleed any air out.

if your booster was bad you'd have a rock hard pedal. like when the engine is off, pump the brakes the pedal becomes rock hard and super hard to push.

bad master would sink to the floor with ease. unless you got a load of air trapped in the system.

Thank you and yes, the bleeders are facing up. The pedal sinks to the floor with ease with the ignition off. There may be air in the system but I've bled and bled them and see no bubbles. When the engine is running I have brakes but just barely it feels like. If the master was bad, wouldn't there be visible fluid? Because there is none

 

[Scottydoggs]

Thank you and yes, the bleeders are facing up. The pedal sinks to the floor with ease with the ignition off. There may be air in the system but I've bled and bled them and see no bubbles. When the engine is running I have brakes but just barely it feels like. If the master was bad, wouldn't there be visible fluid? Because there is none

fluid in the master? it should always have fluid in it.

if the soft pedal started before the new calipers the master is likely bad.

if this all went down after the caliper swap and the master went dry, you introduced air into the master and it will need to be bleed first, you can do it still mounted to the truck. you need two ppl, have the pedal pumper pump the brakes and hold the pedal down, while you crack either line nut off the master, wrap a rag around your wrench cause fluid will shoot out and make a good mess. now snug the line back up and have the pedal pusher let the pedal up and start pumping it again. keep bleeding till you stop hearing it spitting air out. then do the other brake line. then do all 4 brakes. most will say start pass rear, d/r rear, then pass front and finish up d/s front. im not sure any of that matters with newer cars and trucks, but thats how ive done it for 35 years, so why change it up now?

make sure the master stays more then 1/2 full while bleeding it.

i tend to end up working alone a lot, so i made my self a one man bleeder set up. all you need is some clear tubing that fits tight to the bleeder nipple, then make that line like 2 foot long. now get a used clean dry plastic bottle. drill, burn what ever ya got to make a hole in the cap so the line fits through the hole and reaches the bottom of the bottle, then make a smaller pin hole so air can get out of the bottle. fill the bottle 1/4 way with brake fluid, make sure the line is under the fluid, open the bleeder put the hose on it, then you can go pump the brakes slowly, down then up down and up. repeat till theres no more air coming through the clear hose off the bleeder, (with your miles id keep bleeding till clear new fluid is in the line, watch the master level. it can drop pretty fast) snug the bleeder and pull the line off it. repeat on the rest of the brakes.

my diy one man bleeder after a fluid flush. whats nice is you just use a another cap and toss the bottle in the trash or drop the old fluid at the parts store.

 

[Fless]

I suspect that the master was damaged by pushing it to the floor while bleeding. After years of the piston stopping at a certain point -- not to the floor -- pushing the piston past that point likely damaged the seals. It's recommended to place a board on the floor under the brake pedal when bleeding, to stop the pedal from going too far.

 

[03GMCYukonXL]

fluid in the master? it should always have fluid in it.

if the soft pedal started before the new calipers the master is likely bad.

if this all went down after the caliper swap and the master went dry, you introduced air into the master and it will need to be bleed first, you can do it still mounted to the truck. you need two ppl, have the pedal pumper pump the brakes and hold the pedal down, while you crack either line nut off the master, wrap a rag around your wrench cause fluid will shoot out and make a good mess. now snug the line back up and have the pedal pusher let the pedal up and start pumping it again. keep bleeding till you stop hearing it spitting air out. then do the other brake line. then do all 4 brakes. most will say start pass rear, d/r rear, then pass front and finish up d/s front. im not sure any of that matters with newer cars and trucks, but thats how ive done it for 35 years, so why change it up now?

make sure the master stays more then 1/2 full while bleeding it.

i tend to end up working alone a lot, so i made my self a one man bleeder set up. all you need is some clear tubing that fits tight to the bleeder nipple, then make that line like 2 foot long. now get a used clean dry plastic bottle. drill, burn what ever ya got to make a hole in the cap so the line fits through the hole and reaches the bottom of the bottle, then make a smaller pin hole so air can get out of the bottle. fill the bottle 1/4 way with brake fluid, make sure the line is under the fluid, open the bleeder put the hose on it, then you can go pump the brakes slowly, down then up down and up. repeat till theres no more air coming through the clear hose off the bleeder, (with your miles id keep bleeding till clear new fluid is in the line, watch the master level. it can drop pretty fast) snug the bleeder and pull the line off it. repeat on the rest of the brakes.

my diy one man bleeder after a fluid flush. whats nice is you just use a another cap and toss the bottle in the trash or drop the old fluid at the parts store.
View attachment 429514

No I mean wouldn't there be fluideaking out of the master cylinder. Because if the pedal is that far down in figured it would have fluid leaking out. I just don't see why the pedal would sink down with fluid in the master and no leaks anywhere.

Also, I have a one man bleeder myself lol. It looks a lot like yours.

 

[Scottydoggs]

No I mean wouldn't there be fluideaking out of the master cylinder. Because if the pedal is that far down in figured it would have fluid leaking out. I just don't see why the pedal would sink down with fluid in the master and no leaks anywhere.

Also, I have a one man bleeder myself lol. It looks a lot like yours.

if the master leaks its under the base where it mounts to the booster, sometimes they leak, other times they dont. theres seals inside that fail and the plunger can just push in and fluid leaks around the plunger. try bleeding the master. then the brakes. if they still dont work then the master is dead.

 

[rockola1971]

Master is probably ruined AND there is probably alot of air trapped behind the solenoids in the ABS manifold which you cant get out without either locking up the brakes a millions times and rebleeding after or just use a bi directional scanner with the auto bleed function like the tech 2. It uses the ABS pump to pump up your brakes and is a one man job.