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Old 05-07-2019, 06:54 PM   #1
Timtruck
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Avalanche brake failure

A friend of ours, not me, has an '02 Avalanche that has no brakes at all, he replaced the master cylinder, yes it was bled, but the pedal still goes to the floor and wont even pump up. No leaks anywhere either.
I bled the master cylinder for him and it had a good firm pedal then but, when the lines were connected, nothing, right to the floor, I'm stumped. Could it be the ABS, module, pump or sensors?
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Old 05-07-2019, 07:51 PM   #2
95 S_Trucker
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Re: Avalanche brake failure

Did you bleed at each wheel after the master cylinder replacement? Did you perform an automated bleed on the abs unit?
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Old 05-08-2019, 08:54 AM   #3
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Re: Avalanche brake failure

Not sure if this is the same / similar to my 97 Burb. There is an automated bleed that needs to be done on the ABS unit using a Tech II scan tool. An alternate way is to bleed it as good as you can, then try to lock the brakes on a dirt or gravel road. You might be able to try bleeding out the back of the ABS unit first before connecting the lines to the brakes.
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Old 05-08-2019, 11:25 AM   #4
hatzie
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Re: Avalanche brake failure

There are other scan tools that will initiate an automated bleed.
I've done the washboard road trick but it doesn't work as well as the scan tool, if at all, because it's not operating the ABS valves in sequence.
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Old 05-08-2019, 07:28 PM   #5
Timtruck
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Re: Avalanche brake failure

Ok, so a scan tool will be needed. this gets me on the right track, Thanks!
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Old 05-15-2019, 10:41 AM   #6
izzy_Britton
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Re: Avalanche brake failure

i fought my brakes with the same issue for a month. kept asking the same question and kept getting a funny responding question: "did you center the proportioning valve?"

i thought it was one of those funnies, like muffler bearing aand blinker fluid. ya know the kind?

anyways yes, a good scan tool should have something in the menu about an automated bleed or an abs bleed. it is a real thing and yes it will most likely fix your issue, as odd as it sounds. I have an old Solus II from snap-on and it was able to do this.

good luck. update us please. thank you.
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Old 05-15-2019, 11:53 AM   #7
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Re: Avalanche brake failure

Quote:
Originally Posted by izzy_Britton View Post
i fought my brakes with the same issue for a month. kept asking the same question and kept getting a funny responding question: "did you center the proportioning valve?"

i thought it was one of those funnies, like muffler bearing aand blinker fluid. ya know the kind?

anyways yes, a good scan tool should have something in the menu about an automated bleed or an abs bleed. it is a real thing and yes it will most likely fix your issue, as odd as it sounds. I have an old Solus II from snap-on and it was able to do this.

good luck. update us please. thank you.
That's a valid question for folks that are used to working on antiques without ABS brakes.
On the older vehicles you remove the brake warning lamp switch from the combination valve and install a plug after you center the valve shuttle.
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1959 M35A2 LDT465-1D SOLD
1967 Dodge W200 B383, NP420/NP201 SOLD
1969 Dodge Polara 500 B383, A833 SOLD
1972 Ford F250 FE390, NP435/NP205 SOLD
1976 Chevy K20, 6.5L, NV4500/NP208 SOLD
1986 M1008 CUCV SOLD
2000 GMC C2500, TD6.5L, NV4500
2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263
2009 Impala SS LS4 V8


RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.
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