Brake Bleeding?

Whipple1

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Was wondering if our trucks need a scan tool to bleed the brakes properly,it supposed to reset the abs accuator through a cycle then you can bleed,not sure if this is true:confused2: .Ever since I installed my brakes I have an inconsistant brake pedal,when I start it or when I drive around town it feels fine,but when I drive on the parkway wait for a couple of min. depress the pedal it travels twice the distance it should then 1 or two pumps its back to normal,its really unpredictable but it always happens somtimes its high somtimes low,I will try the motive power bleeder next if I dont have to cycle the accuator for the abs.Anyone with info would be great.Thanks
 

JKmotorsports

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There is an automated bleed procedure that uses the scan tool.
If you do not have the JL4 option (Vehicle Stability Enhancement System), then you have to re-initialize the abs system with the scan tool after the automated bleed procedure.
If you DO have the JL4 option, I don't believe you need to perform abs initialization.
But if you have no abs lights illuminated, I would double check to make sure you don't have any trapped air in the system before you move on. You can still manually bleed the base hydraulic system like normal before performing the automated bleed and abs initialization with the scan tool.
 
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unlukky

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And remember to start with the furthest wheel from the master cylinder and work your way to the closest.
ie: RR, LR, RF, LF.
Good luck.
 

Whipple1

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There is an automated bleed procedure that uses the scan tool.
If you do not have the JL4 option (Vehicle Stability Enhancement System), then you have to re-initialize the abs system with the scan tool after the automated bleed procedure.
I do not have stability control,so your saying that I should have to re-initialize the abs system?Im not sure because I called the dealer and they said they dont do that,but that doesnt mean there right,Im still thinking there is air in the lines,I will get a power bleeder and try that.Hey JK unless you have some source thats 100% sure then I will take it somewhere thats familiar with that procedure,Thanks for the help guys.:yesnod:
 

JKmotorsports

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I do not have stability control,so your saying that I should have to re-initialize the abs system?Im not sure because I called the dealer and they said they dont do that,but that doesnt mean there right,Im still thinking there is air in the lines,I will get a power bleeder and try that.Hey JK unless you have some source thats 100% sure then I will take it somewhere thats familiar with that procedure,Thanks for the help guys.:yesnod:

I would say you have air trapped in the system still somewhere from what it sounds like. The abs system wouldn't cause what you are describing (at least I wouldn't think so from my experience). GM tech service and repair procedure guide states the ABS re-initialization is only done if you perform the automated bleed with the scan tool. Manual bleeding of the system doesn't require this.
 

Whipple1

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Well I finally figured out what the cause of the low brake pedal is after installing the Brembo brakes,It wasnt air,the master cylinder or the brake booster, it turned out to be excessive end play in my rear end shafts,it turns out that our posi units in our rears are beyond garbage a time bomb waiting to explode,so what happens is with the rear caliper off I can move my rear axle in and out at least 1/4 of an inch on both sides due to a worn posi unit,You cant feel this play when everything is assembled,So due to a fixed caliper the back and forth play is causing my rotors to compress my caliper pistons inward around turns and swervy driving is when I would get a low Pedal,just like you get when you do a new brake job you have pump the pedal to ceat the pads back to the rotor.Im getting the rear rebuilt completly but with a eaton posi to bullit proof the rear,I know a guy by me thats been building rears for 40 years.So anyone doing brakes check the end play in the shafts there should be very little play,Note: Floating calipers absorb this play dramaticly aposed to fixed calipers,but this is also what can cause a low pedal on our trucks and it is commom.
 

JKmotorsports

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Whipple, makes complete sense now. Not something you would normally look for during a low/spongy pedal diagnosis. Thanks for the useful info. I'm going to check mine when I change my brakes here in the next couple days.
Btw, good to see you around again.
 

Old Goat

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Old thread I know, but wondering if anyone can tell me further info on whether or not I have to do anything as far as ABS scan tool or special bleeding on a 2005 Tahoe with RPO's JL4 (control, Active Brake) and JH2 (Brakes Disc/Disc) ??
 
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