Jon87transam
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- Jan 14, 2011
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This is my first post, and it is long, so please be patient. i own a 99 C2500 suburban, 454,4l80E, G80 14bolt (13 x 3.5 shoes), hydroboost, and overall a real nice find for this style truck. i have owned since may of 09, and came to me bone stock and in exceptional condition with 93,000 miles. truck always runs excellent, but never stopped worth a crap, especially with the largest brakes that gm offered on the rear of any truck, even a 1 ton. i tried lots of ideas: machined all surfaces and installed wagner TQ front pads, hoses, and adjusted rear shoes real tight, new wheel cylinders. complete flush with all new fluid and bleed. left original shoes because they showed little wear and looked very good. truck still stoped marginal. finally noticed that on a 60-70mph stop, i would actually smoke the front pads, and stop way long. brake shop told me to try new shoes as they might be softer than original, and may seat and stop better. also re-machined drums with ultra smooth finish. still no difference. talked to other people and they suggested un-hook kelsey hays abs system. figured i might as well, it wouldn't lock a tire if it had to, even when wet conditions. still little change. swapped wagner tq pad for a mid level pad, still no difference. truck always had good pedal, wasn't stiff. although i was starting to question my hydroboost, i never (and still haven't) changed the booster.
now after all of this i am starting to question my sanity, and how safe it is for my wife and very young child to be in this vehicle. i decided to look for the proportioning valve (pv for short). i found the pv to be located on or in the kelsey hayes abs pump. came to a crossroads: buy more expensive pads and shoes and hope they combat the problem, or change the fluid pressure going to the rear wheels in hope that solves the problem. i talked to lots of gm techs, people on internet that sell high performance frictions, friends in the field, and others having the same problem, albeit, pickups, tahoes, or burbans (i work at napa) and about all said to change the pressure.
now from here on: i will not be responsible if anybody else trys this solution. everybody is on their own, i simply did this out of desperation. some might question the parts i used, or the way i used them, but i feel it is much safer than having a 6500-7000 lb vehicle that is totally useless when it comes to stopping. to all those that might try this, good luck!
first of all, i decided to totally ditch the kelsey hayes abs pump. i re-used everything i could, including all of the lines. all of the lines coming in or out have different threaded fittings, although all front uses 3/16 inverted flare lines, and rear uses 1/4 inverted flare line. the master cyl puts out one line for each front and rear, goes to abs pump, and outputs 2 lines for the front, and one for the rear. in order to re-assemble these parts if this didn't work, i cut approx 1-1.5" (all lines need to be even) off of each line at the abs pump, except for the output for the rear brakes, as you can reuse that fitting. i used a 1/4 female pipe thread "T" with 3 - 1/4 male pipe thread 90* fittings that convert to 3/16 compression. if you would set the "T" on the table with sides pointing out, and one pointing up, you would set all 3 - 90* 1/4 pipe to 3/16 comp facing yourself in the same direction. i used that setup for the front brakes as you will find it works well for the input/ouput from the abs pump. as for the rear line: i use a 1/4 compression union and made a new line in the shape of a "S" and brought that new line up where the abs pump used to sit. i then used a Jegs adjustable proporting valve, make sure to follow in and out, and then brought it out to a "U" shaped line to double back from where it came from under the new adj pv. from there it went into a jegs 2-3lb residual valve that the output of it actually just threads right onto the odd thread size of the output rear line. i did have to machine a bracket to hold the "U" shaped line as it got really bouncy with the added weight and length traveled. it says to start out with the valve at 1/2 of its full travel. proceed to bleed as normal, check for leaks, then test drive in open area. i ended up adding more pressure than half, but now i can actually lock the rear wheels on dry pavement if i push hard enough, a task that was never accomplished with factory setup. i can now allow for towing a load on a trailer without trailer brakes and adjust the valve accordinly. it works great.
i know some of you will say never use compression fittings, or pipe thread, but the hell with it. i used thread sealer on a the threaded connections, and the compression fittings were used properly. i can still re-install the abs pump in the future, although i'll have to compression the ends of the lines back on. i'm sure somebody will say i should have flared the fittings, but millions of older cars and especially trucks on the roads today have compression fittings on brake lines, and i personally haven't heard of any failures. i think there is a better chance the line will rust out before a compression failure. to each their own. and besides, pipe thread was commonly used on older cars, trucks, and heavy duty trucks for years and years before the flare fitting was invented.
i also pulled the dash cluster, removed the abs and brake warning bulbs twist outs, pulled the bulbs, and reinstalled the twist outs. i got tired of looking at the lights always being on. at this time i do not have pics of my work, however if there is enough response to this thread, or questions from people wanting to try this, i will submit some. i think it turned out great. it doensn't look sloppy at all. again, sorry for the long post, i only did this post in hopes it might help somebody else.
happy motoring
now after all of this i am starting to question my sanity, and how safe it is for my wife and very young child to be in this vehicle. i decided to look for the proportioning valve (pv for short). i found the pv to be located on or in the kelsey hayes abs pump. came to a crossroads: buy more expensive pads and shoes and hope they combat the problem, or change the fluid pressure going to the rear wheels in hope that solves the problem. i talked to lots of gm techs, people on internet that sell high performance frictions, friends in the field, and others having the same problem, albeit, pickups, tahoes, or burbans (i work at napa) and about all said to change the pressure.
now from here on: i will not be responsible if anybody else trys this solution. everybody is on their own, i simply did this out of desperation. some might question the parts i used, or the way i used them, but i feel it is much safer than having a 6500-7000 lb vehicle that is totally useless when it comes to stopping. to all those that might try this, good luck!
first of all, i decided to totally ditch the kelsey hayes abs pump. i re-used everything i could, including all of the lines. all of the lines coming in or out have different threaded fittings, although all front uses 3/16 inverted flare lines, and rear uses 1/4 inverted flare line. the master cyl puts out one line for each front and rear, goes to abs pump, and outputs 2 lines for the front, and one for the rear. in order to re-assemble these parts if this didn't work, i cut approx 1-1.5" (all lines need to be even) off of each line at the abs pump, except for the output for the rear brakes, as you can reuse that fitting. i used a 1/4 female pipe thread "T" with 3 - 1/4 male pipe thread 90* fittings that convert to 3/16 compression. if you would set the "T" on the table with sides pointing out, and one pointing up, you would set all 3 - 90* 1/4 pipe to 3/16 comp facing yourself in the same direction. i used that setup for the front brakes as you will find it works well for the input/ouput from the abs pump. as for the rear line: i use a 1/4 compression union and made a new line in the shape of a "S" and brought that new line up where the abs pump used to sit. i then used a Jegs adjustable proporting valve, make sure to follow in and out, and then brought it out to a "U" shaped line to double back from where it came from under the new adj pv. from there it went into a jegs 2-3lb residual valve that the output of it actually just threads right onto the odd thread size of the output rear line. i did have to machine a bracket to hold the "U" shaped line as it got really bouncy with the added weight and length traveled. it says to start out with the valve at 1/2 of its full travel. proceed to bleed as normal, check for leaks, then test drive in open area. i ended up adding more pressure than half, but now i can actually lock the rear wheels on dry pavement if i push hard enough, a task that was never accomplished with factory setup. i can now allow for towing a load on a trailer without trailer brakes and adjust the valve accordinly. it works great.
i know some of you will say never use compression fittings, or pipe thread, but the hell with it. i used thread sealer on a the threaded connections, and the compression fittings were used properly. i can still re-install the abs pump in the future, although i'll have to compression the ends of the lines back on. i'm sure somebody will say i should have flared the fittings, but millions of older cars and especially trucks on the roads today have compression fittings on brake lines, and i personally haven't heard of any failures. i think there is a better chance the line will rust out before a compression failure. to each their own. and besides, pipe thread was commonly used on older cars, trucks, and heavy duty trucks for years and years before the flare fitting was invented.
i also pulled the dash cluster, removed the abs and brake warning bulbs twist outs, pulled the bulbs, and reinstalled the twist outs. i got tired of looking at the lights always being on. at this time i do not have pics of my work, however if there is enough response to this thread, or questions from people wanting to try this, i will submit some. i think it turned out great. it doensn't look sloppy at all. again, sorry for the long post, i only did this post in hopes it might help somebody else.
happy motoring
