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Discussion Starter #1
ever since i did the brake pads/rotors on my 2002 silverado 1/2 ton i have constantly had problems stopping. the rotors are the exact same specs as stock but slotted and i have hawk pads. at first they were really bad and a local garage told me to add a proportioning valve to the rear brakes to boost the pedal pressure...did jack shit. then the rotors were glazed with 1000 miles on them so i had them turned down and bought new pads because i wanted to be sure it was right and the pads were glazed too. then i did stainless steel brake lines...helped with stopping but pedal pressure and height still sucked. and i was just under my truck and next to the transfer case, and torsion bar on the drivers side attached to the frame there is a black box with brake lines going into it, and it has 2 plugs one big one and one small i unplugged both of them and took it for a ride and thought my head was going to go through the windshield they worked soo good and the pedal was nice and firm. and i obv know i cant leave it like that i was just troubleshooting but what could cause the brakes to be shitty with it plugged in? is it a sensor that isnt doing its job correctly? what can i do...?
 

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Ballin' on a Budget
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I'm assuming it's the mechanical part of the abs system. I dont know why it would be let the fluid give without sensing slip. Do you have different size tires front to back?
 

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The black box is your ABS pump. Do you have 4 wheel disks? GM went back to disk/drum on the trucks in 05 because of such a shitty pedal. Anyway, it may be that the ABS pump is going bad or has crap in it. When you did the brakes, did you just push the caliper piston back in it's bore? The proper way is to clamp the line, open the bleader valve and then reset the piston. This way, all the junk that has setteled into to calipers is not pushed back into the ABS pump, but flushed out. I have seen too many pumps ruined because of doing a brake job the "old school' way. As for the pro valve, it LIMITS pressure to the rear wheels to prevent lock up, it does not increase it. Bleed the lines real good, it sounds like you may have air in the system. As for the glazing, did you overheat the rotors and pads before they got seated good? 1000 miles sounds real quick to glaze up and set of pads.
 

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Discussion Starter #4
The black box is your ABS pump. Do you have 4 wheel disks? GM went back to disk/drum on the trucks in 05 because of such a shitty pedal. Anyway, it may be that the ABS pump is going bad or has crap in it. When you did the brakes, did you just push the caliper piston back in it's bore? The proper way is to clamp the line, open the bleader valve and then reset the piston. This way, all the junk that has setteled into to calipers is not pushed back into the ABS pump, but flushed out. I have seen too many pumps ruined because of doing a brake job the "old school' way. As for the pro valve, it LIMITS pressure to the rear wheels to prevent lock up, it does not increase it. Bleed the lines real good, it sounds like you may have air in the system. As for the glazing, did you overheat the rotors and pads before they got seated good? 1000 miles sounds real quick to glaze up and set of pads.
yes, i have 4 wheel disk its an 02 1/2 ton. when i did the brakes i did not clamp the line and open the bleeder valve tho:pissed: i didnt know you had to till after:think:. with that said what part of the abs would that ruin because i will replace it...and im sure there is no air in the system a local shop bleed them then the dealership to be sure...the glazing on the rotors is gone now...how long do they have to "seat"...also if i replace the abs pump will this solve my problem???
would it be a bad idea to just leave my abs pump wires unplugged(the 2 plugs going to it) like would it ruin or hurt anything because i like the brakes the way they are with it unplugged and abs in my opinion is for people who dont know how to drive anyways...
 

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Discussion Starter #5
oh yea JGPSILVERADO: the pro valve limits the pressure to the rear brakes?!? the reason i put it in is because my pedal was soft and i was told it would boost the pressure to the rear which would help the pedal stiffness since the my pedal was soft.
Also when i disconnected my abs pump my brakes were good but my rear wheels kept locking up because they were working harder than the front but i think what im going to do is get a new abs pump and get rid of the prop valve goin to the rear...what do you guys think?
 

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Yes, the pro valve limits pressure to the rear wheels. During a stop, the wieight shifts forward applying more pressure to the front wheels than the rear, so you need less rear brake pressure. Did you add a proportioning valve or replace the one you already had? As for replacing the ABS pump, get it looked at by a tech and make sure it is the problem before replacing it. It is not cheap. Please understand, I am not there and can only go by what you tell me, and my experiance. I don't want you just throwing parts at your truck. It can get real expensive real fast. These late model ABS systems are good, but complex and next to inpossable to diagnose without being there. Let me know if there's anything else I can help with.
 

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Discussion Starter #7
Yes, the pro valve limits pressure to the rear wheels. During a stop, the wieight shifts forward applying more pressure to the front wheels than the rear, so you need less rear brake pressure. Did you add a proportioning valve or replace the one you already had? As for replacing the ABS pump, get it looked at by a tech and make sure it is the problem before replacing it. It is not cheap. Please understand, I am not there and can only go by what you tell me, and my experiance. I don't want you just throwing parts at your truck. It can get real expensive real fast. These late model ABS systems are good, but complex and next to inpossable to diagnose without being there. Let me know if there's anything else I can help with.
well when i unplug the abs pump wiring the rear wheels are gettin too much braking because they are lockin up on me...and i didnt replace the one in there i added a second universal pro valve to the rear brakes because it was said to "boost the pedal pressure", i dont know if this may affect it but the valve is located going to the rear right under my extended cab door obv on drivers side because thats where the lines are! ha. and i got a price on one for 400+shippin fro gmpartsdirect.com so its pretty expensive and i would deff have a tech look at it first at the dealer...as for you throwing parts at my truck your just tryin to help me out bro and point me in the right direction no blame is on you for anything!
Also do you know if this is the p/n the guy at the dealer who i was tryin to get the p/n from didnt know if it was or not?!? anyways 88964302...if not i dont know where you could look it up because he said there different for different last 8 of the vin and mine is 21415378 if that helps...?:shake:
 

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Discussion Starter #9
ok, having a problem. which part do i need to fix my problem the module or the valve?!? because i called a dealer and, i e-mailed gmpartsdirect.com and both gave me p/n 88964302 which when i type it in at gmpartsdirect.com it says "VALVE". but the p/n JGPSILVERADO gave me 88982286 lists as "MODULE"...just dont want to go spend $500+ on a part and have it be the wrong thing ya know...thanks guys!
 

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Alright.

Number one. Don't assume a black box is bad because the brakes are better with it unplugged.
Number two. The bleeders on this application do not need to be opened to bleed the brakes. ( I have 13 full size GM's in the fleet, some with 180k miles or better so I can say this for sure.)
Number three. Never add a component (additional proportioning valve) to the hydraulic ABS brake system on your truck while in search of a problem. Or ever for that matter, unless the truck has specialized off-road only applications.

Now that we've gone through all the things you should already know, here's the important one.

THERE IS NO WAY TO COMPLETELY BLEED THE AIR FROM THE ABS IN THESE TRUCKS WITHOUT THE USE OF A COMPUTER INTERFACE (USUALLY THE DEALER) WHILE BLEEDING . The computer is used to instruct the ABS module to open it's valves allowing complete removal of the air. If you had the brake system open and allow even the smallest amount of air into the lines, not only will the performance suck, IT CAN KILL YOU.

Call the dealer and schedule a brake bleeding while interfaced with a tech 2 controlling the ABS while bleeding. I typically pay 1hr shop rate for this service, but only have two dealers smart enough to do it.

With that said, PLEASE have the brakes professionally bled, PLEASE.
 

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Discussion Starter #11
Alright.

Number one. Don't assume a black box is bad because the brakes are better with it unplugged.
Number two. The bleeders on this application do not need to be opened to bleed the brakes. ( I have 13 full size GM's in the fleet, some with 180k miles or better so I can say this for sure.)
Number three. Never add a component (additional proportioning valve) to the hydraulic ABS brake system on your truck while in search of a problem. Or ever for that matter, unless the truck has specialized off-road only applications.

Now that we've gone through all the things you should already know, here's the important one.

THERE IS NO WAY TO COMPLETELY BLEED THE AIR FROM THE ABS IN THESE TRUCKS WITHOUT THE USE OF A COMPUTER INTERFACE (USUALLY THE DEALER) WHILE BLEEDING . The computer is used to instruct the ABS module to open it's valves allowing complete removal of the air. If you had the brake system open and allow even the smallest amount of air into the lines, not only will the performance suck, IT CAN KILL YOU.

Call the dealer and schedule a brake bleeding while interfaced with a tech 2 controlling the ABS while bleeding. I typically pay 1hr shop rate for this service, but only have two dealers smart enough to do it.

With that said, PLEASE have the brakes professionally bled, PLEASE.
well, if you actually read whats going on you would have realized that in comment #4 i clearly said the dealer blead the brakes already...? And just like stated above you cant just diagnose the problem like that without acutually seeing it what if my truck is having a problem one of your 13 trucks doesnt have?!? how do you know the black box isnt bad?
 

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well, if you actually read whats going on you would have realized that in comment #4 i clearly said the dealer blead the brakes already...? And just like stated above you cant just diagnose the problem like that without acutually seeing it what if my truck is having a problem one of your 13 trucks doesnt have?!? how do you know the black box isnt bad?

I didn't mean to put you on the offensive, but brakes are the most important system on your truck, period. But, most dealers I've dealt with have no concept of how to bleed the air from the ABS correctly. It took 4 dealers and two accidents to get it solved.

Brakes working better after unplugging the ABS module can only be one thing:
1. False signals from a front WSS (wheel speed sensor) Anything else would activate the ABS lamp and throw a fault code.

Low pedal height can only be two things:
1. Air in the system.
2. Binding brake pads or hardware.

The number one cause of poor braking performance on all my used and abused trucks has been corrosion somewhere.

As for the brakes being better after unplugging the ABS, one or both of your front WSS (wheel speed sensor) has either failed or has corrosion under it's mounting flag causing the sensor to move away from it mount slightly fooling the ABS to activate early, or a front wheel bearing is failing. I think you would have noticed the front wheel bearing loose after you jacked the truck up though.. The WSS is a very common problem and there are many people out there with this problem. Heck, there is even a recall on your year truck, but only in the Rust-belt states. The dealer is the fastest way to determine which one WSS is bad.

In summary, you most likely have two problems:
1. Repair or replace the WSS first. (electrical)
2. Then, attack pedal height second. (air)

Please don't think I'm preaching or that I'm a know-it-all, but $3600 spread out over TWO "air in the ABS system" accidents is enough for me to be a little vocal.
 

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And, I almost forgot, before doing any of the above, if those 20" wheels have a different rolling diameter than the stock size, have the dealer reprogram the tire diameter BEFORE any of the above is tested. The tire diameter is essential to the operation of your ABS equipped truck even when ABS is not activated (normal braking.) This is because your truck has electronic brake proportioning that is also controlled by the ABS module.
 

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Discussion Starter #14
nah bro my bad im not offended just in a bad mood about it because i just havent been able to figure it out. JGPSILVERADO said if you dont clamp the brake line when you compress the caliper piston otherwise all the junk in the caliper piston gets forced into the sensors of the abs pump therefore making false signals...and idk about the wheel speed sensor thing because this happened when i first did brakes/rotors so could i have fucked up a sensor when i did the brakes? i mean or do they just go bad because the chances of doing the brakes the same day they go bad is pretty slim i would bet...?
 

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...and idk about the wheel speed sensor thing because this happened when i first did brakes/rotors so could i have fucked up a sensor when i did the brakes? i mean or do they just go bad because the chances of doing the brakes the same day they go bad is pretty slim i would bet...?
Now were cookin'... Yes, I believe you may have damaged a WSS while doing the front rotors.

However, have your dealer check your truck for RECALL concerning the front WSS's. If you live in Mass. and the you haven't had the recall done, your in luck. If the truck was sold in a state not listed in the recall, and you live in a recall state, explain that to your dealer and GM will still cover it.

Otherwise, it's about $120 a sensor and there is a way to test them with an OHM meter but I'll have to search for the procedure (I saw it here or another forum) so you will only have to change the bad one, not both.
 

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Discussion Starter #16
when i brought to get my brakes blead they said there was a recall...then they said they wouldnt do it because i had aftermarket rotors:pissed:.
 

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when i brought to get my brakes blead they said there was a recall...then they said they wouldnt do it because i had aftermarket rotors:pissed:.
The replacement of your rotors cannot affect the recall. If your dealer's service writer can't understand, perhaps the service manager can. If all else fails, call the 800 number in your service manual, and explain to them that your local dealer won't honor the recall.
 

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Discussion Starter #18
will do...and i scheduled to have the dealership re-bleed my brakes to make sure for nothin...will get back to ya and let you know...:shake:.
 

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will do...and i scheduled to have the dealership re-bleed my brakes to make sure for nothin...will get back to ya and let you know...:shake:.

I wouldn't have them rebleed the brakes until the WSS is addressed.
After normal braking is restored (when they fix the WSS's), activate the ABS on an empty gravel road from about 8mph. If the pedal drops as the ABS activates, then there is still air in the system. If the pedal stays the same, but simply vibrates, then there is no air in the system.
 
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