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Hello Everyone,
I just did some brake work on my buddies 2008 GMC Sierra 1500 4.8L Base truck and I cannot get a solid brake pedal. He had let it sit for a year and the front calipers seize up and I couldn’t even compress them. Also the rear drum brake shoes where down to the metal. I went a head and replaced the drums, shoes and had to replace the rear drive side wheel cylinder because it had a casualty when trying to remove the stuck on drums. I adjusted them properly and the the self adjusted is working freely. I then moved on and replaced the front calipers and pads. I then bleed the brakes/ I wasn’t getting good pedal and it keeps traveling strait to the floor. I used my Autel scanner to run through the ABS bleed procedure on each wheel and still not any peddle. I am getting a ton of air and the fluid coming thought my one man bleeder tool hose is all foamy and filled with air on the front calipers. The rear wheel cylinders the fluid looks good with no air on both sides when bleeding them. After a couple bottles of new brake fluid being run though the system in the attempt to get the air out out of the front calipers it has gotten a little better but still very low peddle feel. When driving the vehicle it stops, but the peddle is almost to the floor. If you double pump the brake peddle when coming to a stop it has brake feel like it should at the top of the peddle, but returns to the floor on the next stop. I’ve checked for leaks everywhere and I am not losing fluid level in the reservoir. The truck has 103,000 miles on it currently. No codes in any of the systems.
I have done tons of brakes in my life and bled many brakes systems with all the lines that rot out where I live and have never had this much problems getting brake peddle to build of pressure. At this point I am thinking bad master cylinder or maybe one of the calipers I got from Advance Auto is bad? Thanks for reading guys!!!
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I’ve replaced some calipers on my vehicle before and had to run through the bleeding process through my computer to properly do it as well.
I’d say the caliper is not the problem since it’s not leaking and the brakes do work still. I bet there is still air somewhere in the lines.
You said you’re familiar with brake work, but is it possible when you ran the procedure that you bled the calipers out of order?Did you pull out all the old brake fluid from the reservoir before bleeding and did you notice if it was dirty, how dirty if it was? If you didn’t remove it, the dirty fluid could damage the master cylinder.
When you double pump the brakes to get them to feel like normal, does the pedal move towards the floor at all when you hold it in place?
If not, your master cylinder is likely not the issue.Can you extrapolate on your bleeding method? If do you keep the bleeder valve wide open through the whole process or do you pump the brakes, then hold the pedal down with something, then open and close the bleeder valve?
Also,in my experience, using a one man bleeder can be deceiving if you don’t have the hose around the nipple as tight as it can be, letting air from outside get in where the hose sits over the the bleeder valve. This can make it seem like you’re removing more air than you are. I use a zip tie over mine, but even then it leaks occasionally.
Back brakes work OK ?
Problems with only the front brakes .
I am guessing the problem is with the part of the master cylinder that operates the fronts . Or the part of the ABS that operates the front .
You keep getting air when you bleed the fronts ?
I have read about gravity bleeding brakes . At least for most of the bleeding process .
Also might look at one of these kits ;
http://www.harborfreight.com/catalogsearch/result?q=brake+bleed
If you still have problems , my gut tell me master cylinder
God bless
WyrDue to the design of the ABS pump, there is a special automated bleeding procedure for the front wheels of these vehicles. It can only properly be done with GM’s Tech II tool because it has the correct solenoid sequencing procedure programmed into it. Other tools, like your Autel, won’t get it done. So, you may need to have the dealer do the bleed unless you know someone else with a Tech II.
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