george88gta

iTrader: (2)

Truck is an 03 Silverado 1500 4wd WT. It was used as a snow plow truck before I purchased it and its main use is still snow plowing. Needless to say it had the rusted brake lines issue. Prior to replacing the lines, it had very little stopping power. About 12k ago, I replaced the master cylinder, vacuum booster and pads and rotors. Brakes were passable, but never really great. I just replaced all the steel lines with a kit from Chevy. While I was in there, I replaced the rear calipers, all 4 wheel pads, parking brake shoes and all the hoses.Should be great right? Wrong. Pedal is OK, but the rear calipers do not seem to be releasing. Very difficult to turn the rear rotors by hand. I checked the rear rotor movement after installing the parking brake shoes, no problem. As soon as I install the rear calipers, and apply the brakes, the rotor cant be turned by hand. First thought was a defective caliper, but what are the odds of getting two defective calipers? Could the steel lines be reversed? The rear of the MC goes to the front of the proportioning valve and front output ( from the proportioning valve ) goes to the lower left port of the ABS module.

arthursc2

iTrader: (5)

I don't know that this will help your specific issue, however I am pretty certain the front output from the MC goes to the front brakes. I can verify in a sec when I go to the garage.

You're pretty specific to say caliper is causing the issue, and I trust your diagnosis: but I have always had a shitty time adjusting the parking brake on these drum in hat designs.

Another thing that could be happening here is that the SUV rotors are bigger than the truck. Any chance you have an SUV rotor in there and the caliper is binding on the OD of the rotor?

I'll report back about the lines in a sec

george88gta

iTrader: (2)

Thanks for the reply. The rotors have been on the truck for about 12,000 miles, all I did was clean them up, so I am comfortable that they are not the problem. When I installed the parking brake shoes, I made sure that the rotors tuned freely before I installed the calipers ( I install 1 lug nut to align the rotor to the axle flange). The shop manual has an illustration that shows the MC lines crossing over and the rear output goes to the front of the proportioning valve. One other piece of information. When the rotors didnt turn freely, I opened the bleeder screw and let some fluid run out. It ran freely, but the rotor didnt free up. I am guessing that it isnt fluid pressure and more than likely mechanical ( just a guess). Getting too old for this stuff!

Hillbilly Silverado

iTrader: (1)

https://www.performancetrucks.net/forums/gmt-800-older-gm-general-discussion-130/easy-abs-delete-531531/

That has a picture of the ABS routing. Double check your line routings.

Check your calipers and make sure the piston isn't hanging out too far.

The only other thing I can think of for you to check is your brake pad clearance and make sure the pads aren't causing the issue. Run a feeler gauge in there and see if it's touching or hanging and the pad isn't caught on those brackets or something. Seen this once before at the mechanic I use to use on a Tahoe. Somehow they got the wrong pads or something and they would slip on but would bind the rotor once they were tightened. Returning the pads and getting new ended up fixing it for them.

george88gta

iTrader: (2)

Thats how I have my lines installed. I will check to verify that I have the lines leaving the proportioning valve correctly.

Hillbilly Silverado

iTrader: (1)

I never had a proportioning valve on mine. I have a 99 ECSB NBS. Mine was completely stock when I overhauled my brakes.

I only had the ABS unit that my brake lines went in too. I deleted my ABS unit and the brakes work perfect. All discs brakes on 4 corners. No proportioning valve just the ABS

george88gta

iTrader: (2)

Latest info. I verified line routing and I believe it to be correct. If anyone can supply an accurate/clear diagram, I would be grateful. Anyway, the truck stayed on the lift overnight. I checked the drag on the rear rotors and I could move them. Took a some effort, but they moved. Tranny was in neutral. I partially collapsed the calipers and the rotors moved easier. Parking brake wasnt adjusted yet and rotors moved OK so I guess the parking brake isnt in the equation. I applied the brakes several times and I could still move the rotors by hand. Installed the wheels and as would be expected, the wheels moved very easily. I adjusted the parking brake cable and no noticeable increase in drag. Went for a ride, no noises, truck coasts just fine and no burning smells. So what was different from yesterday? Only thing I didnt do today was to perform the ABS bleed procedure. I had to do it several times to get a good pedal. The Tech II didnt indicate any codes or errors from the ABS system. Guess this is on hold for a while to see if problem reoccurs. Thanks for the help.