04 Yukon, can't get brakes bled.

[Jeremy_K]

I recently put a new caliper on the driver rear and new pads and rotors on the rear brakes. I also flushed the black fluid out of the lines and tried pressure bleeding starting from the pass. rear with no luck. I couldn't get the fluid flowing into the container. So I had a buddy pump and bleed that way. Took it for a drive and had a very low pedal. Then I blew a brake line. I had a mechanic friend install all new lines and he also did the traditional brake bleed. I drove it home and the pedal is still low as hell. I have the hydro boosted garbage. I'll never buy another vehicle equipped with it again. Am I missing an important step here? I've been doing brakes for many years and never had this many problems.

 

[BlackOh7on22s]

Gotta use a TechII to do the bleed procedure with b/c of ABS

 

[David Paul]

Humm. I have an 04 Tahoe, hydroboost. I've replaced brake line, calipers etc, and never had a problem bleeding the system. I can't imagine how the hydro could cause a problem with bleeding the system. Never used the Tech2, have heard you need it for abs, but I still have a firm pedal.
Master cylinder?

 

[hoaxci5]

I had to cycle the ABS after replacing my rear calipers on my 01. Low speed and jam the brakes, or find a dirt road. That fixed my low pedal.

 

[#1taho]

hydro boost is great, way better breaking than a traditional vacuum booster. But I replaced all my lines and they blead fine. you may need a master cylinder or have air in the abs pump. After I blead my lines my pedal was low for the first few km, then went back to normal. I have heard of guys bleeding with the key on, may want to try that.

 

[Gtir007]

Definitely air in the abs pump, you can also use a otc genesys

 

[SLCHOE]

Lift the rear of the truck a little higher than the front and do an ABS bleed via scantool. Then bleed both rears first.

 

[Red Rider]

is there a write up on bleeding brakes with ABS. Last time i did it, i just pumped traditional way. evidently, that may not be best way?

 

[rockola1971]

is there a right up on bleeding brakes with ABS. Last time i did it, i just pumped traditional way. evidently, that may not be best way?

i did a quick and dirty one a little over a month ago here. Let me see if i can find it. Gravity Bleeding works just fine, just takes alot of time. Trick is you have to get the abs pump to cycle a few times to get the air out of it. I used the below procedure on a 03 Tahoe 5.3L FFV. It had major corrosion and had a pinhole blowout on the line that goes from master cylinder to the ABS manifold for the front brakes.

Here is a copy that I wrote in a thread concerning ABS component replacement.

Have someone pump the brakes up like old school method and go around and bleed as normal. Then move the hoe in the driveway a few feet and lock the brakes up a couple times. Then bleed again old school. Wont hurt to lock em up again and bleed again. This moves air out of ABS system (pump, manifold, etc). Start again with farthest from the master cylinder and one caliper at a time. Crack the bleeder open just enough to get a little fluid and leave open for around an hour. Make sure master cylinder is always topped off during each caliper bleed. Once you finish up with all 4. You should have good pedal. If not, lock em up again and repeat. I locked them up twice after regular bleed then gravity bled every tire and thats all it took. I had all 4calipers off and replaced. One line from front to ABS manifold replaced and it was all good to go.

Or see my other thread about the ****** clone GM Tech 2 which has the auto bleed feature that the dealership mechanics use when a vehicle is bled in the dealership service Dept. $240 or so and it does much more than just that! Itll pay for itself in less than a year easily.

 

[iamdub]

First off, hydraboost is da ******* and has nothing to do with issues with bleeding.

Secondly, if that rear caliper is not defective and there are no leaks anywhere, the problem is likely the master cylinder. Of course, you wanna make sure the ABS module is bled. I've always bled as best as I could the traditional way, except ever so often I'd turn the key to "on" just as I started to push the pedal down. I'd pump a couple of times and repeat this a few times. I've never had a helper when I bled. I've always hung a plastic water bottle with a clear hose going through the cap all the way to the bottom of the bottle and the other end of the hose slipped over the bleeder. Anyway, I bleed them like this cuz the ABS solenoids are cycled during a test when you first turn the key on. If I feel it needs more or I'm just bored, I take the car to a grassy lot and hit the brakes to activate the ABS a few times, then bleed again. If you still have a soft pedal, change the master cylinder.

I just did a brake job on my '08. All the corners bled fine until I got to the last one (front left). The pedal suddenly felt odd during a stroke and would never get firm again. I started the bleeding process all over again and there was air again at the back calipers and the pedal just would not firm up. After some interwebz digging, I rushed to O'Reilly's for a new master cylinder (it was only $10 more than the remanufactured one and included a new reservoir). This fixed it. I couldn't believe that it was pure coincidence that the MC just so happened to have so many strokes left in it and they were used up during that bleeding process. This was kinda the case, but not exactly. Over time, the bore and piston seal(s) inside the MC wear just in the area where the piston has been cycling for the past 1xx,*** miles. When bleeding during a brake job, the piston is pushed much farther than it's normal travel and into the rarely- or never-touched area of the bore where it's tighter. The aged seal(s) on the piston catches in the smaller/tighter bore and gets torn or peeled out of place. Some mechanics place a block of wood behind the brake pedal to limit it's travel during the bleeding process.