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 Post subject: bleeding ABS
 Post Posted: Fri Nov 07, 2008 6:31 pm 
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31's
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Joined: Mon Mar 05, 2007 5:33 pm
Posts: 191
Location: West Milford, New Jersey
so i just replaced the master cylinder on my truck to end the whole brake fade problem that i had but i dont know how to bleed the abs unit. actually the all the repair manuals ive read for the truck dont give any info on bleeding the unit. i just disconnected the powersupply for now but need to know how to bleed the unit because the brakes are still spongy even after bleeding almost two quarts of new fluid through

the truck is a 94 blazer

_________________
1994 Jimmy, bullet proof 4L60E, Posi-Lock, Cooper Discoverer STT's, 55w Hella 500's, Camoclad Camo, Magnaflow Cat, Dynomax catback exaust, mostly stock but still takes a beating


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 Post subject: Re: bleeding ABS
 Post Posted: Fri Nov 07, 2008 10:23 pm 
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235's

Joined: Thu Jan 24, 2008 5:04 pm
Posts: 39
Location: Bridgeton, New Jersey
DID YOU "BENCH BLEED" THE MASTER CYLINDER BEFORE INSTALLING IT? DO YOU HAVE 4 WHEEL ABS OR JUST REAR? I PUT IN BOTH ANYWAYS(I couldn't put in the figure(picture) of the unit for the 4 wheel system if you need it i can email it to you or whatever works). LET ME KNOW IF THIS FIXES IT BUT I THINK YOU FORGOT TO BLEED THE MASTER.


Right from ALLDATA: (for a 1994 Blazer)

Master Cylinder Bleeding

This procedure can be performed with master cylinder on or off vehicle.

1. Disconnect brake lines at master cylinder, if necessary.
2. Connect suitable lengths of brake lines to master cylinder and immerse other ends of lines in master cylinder reservoirs.
3. Apply master cylinder pushrod or brake pedal with full strokes until air bubbles have disappeared in reservoirs. It may require 20-30 applications to fully eliminate air bubbles.
4. Remove bleeding lines from master cylinder, then install master cylinder on vehicle, if necessary, and connect brake lines. It is not necessary to bleed entire hydraulic system after replacing master cylinder, providing master cylinder has been bled and filled during installation.



Also from ALLDATA:

Four wheel ABS bleed procedure:

MANUAL BLEEDING
The Electro-Hydraulic Control Unit Brake Pressure Modulator Valve Module (EHCU/BPMV) should be bled after replacement or if air is trapped in the unit or system. If system bleeding is required, the module must be bled thoroughly before the wheel cylinders and calipers.

There are two bleeders on top of the unit that appear to be normal bleeders (figure 221). These are modulator bleeders and must remain closed when the unit is not pressurized.

The internal bleeders are on either side of EHCU/BPMV module. The valves are used to open the internal passages within the EHCU/BPMV module. Both bleed valves must be rotated 1/4 to 1/2 turn counterclockwise before beginning the bleed process. The valve on the lefthand side is used for the rear brakes and the valve on the righthand side is used for the front brakes.

NOTE: The ignition switch must be in the Off position or false diagnostic trouble codes may be stored.

SPECIAL TOOL REQUIRED (or equivalent)

* J-39177, Combination valve pressure bleeding tool (three required).

PROCEDURE

1. Install combination valve depressor tool J-39177 to LH high pressure accumulator bleed stem of EHCU/BPMV module.
2. Install combination valve depressor tool J-39177 to RH high pressure accumulator bleed stem of EHCU/BPMV module.
3. Install combination valve depressor tool J-39177 to rear combination valve.
4. Ensure master cylinder fluid level, fill if required.
5. Bleed EHCU/BPMV module as follows:

1. Slowly depress brake pedal one time and hold.
2. Open left modulator bleeder, until fluid flows clearly or pedal is depressed, the close left bleeder.
3. Slowly release brake pedal.
4. Wait 15 seconds, then repeat steps until all air is bled from EHCU/BPMV module.
5. Close LH internal bleed valve. Torque bleed valve to 7 Nm (5 ft lbs) .
6. Repeat preceding bleed steps for righthand bleed procedure.
7. Remove special tools.

6. Ensure master cylinder fluid level, fill if required.
7. Bleed wheel cylinder and calipers.
8. Turn ignition key to On position, then perform 3 function test with TECH 1 scanner.
9. Check brake pedal feel and braking performance; repeat procedure if required.




Then rear wheel ABS from ALLDATA:

Rear Wheel Anti-Lock Brake System

The ignition switch must be in the Off position or false diagnostic trouble codes may be set to memory.

1. Install bleeding tool No. J-39177, or equivalent, on combination valve.
2. Check master cylinder reservoir fluid level and fill if necessary.
3. Relieve vacuum reserve by pumping brakes several times.
4. Fill master cylinder reservoirs with suitable DOT 3 brake fluid. Maintain fluid level during bleeding.
5. If master cylinder is suspected to have air in the bore, bleed it before any wheel cylinder or caliper as follows:

1. Disconnect forward brake pipe connection at master cylinder and allow brake fluid to flow from connector port.
2. Connect brake pipe but do not tighten.
3. Slowly apply brake pedal and allow air to bleed from loose fitting, then tighten fitting before releasing pedal.
4. Wait 15 seconds.
5. Repeat this sequence until all air is purged from master cylinder bore.
6. Repeat procedure for rear pipe.

6. Bleed each wheel in the following sequence:

1. Right rear.
2. Left rear.
3. Right front.
4. Left front.

7. Attach tool No. J-28434, or equivalent, to wheel cylinder/caliper bleeder valve. Immerse opposite end of hose into suitable container partially filled with brake fluid.
8. Slowly apply brake pedal one time and hold.
9. Loosen bleeder valve to purge air from wheel cylinder/caliper.
10. Tighten bleeder valve and slowly release pedal.
11. Wait 15 seconds.
12. Repeat sequence until all air is purged from wheel cylinder/caliper.
13. Torque bleeder valve to 62 inch lbs.
14. Perform preceding bleed steps at each wheel until system is bled.
15. Check brake pedal for sponginess and the brake warning lamp for indication of unbalanced pressure. Repeat bleeding procedure to correct either condition.


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 Post subject: Re: bleeding ABS
 Post Posted: Sat Nov 08, 2008 3:27 pm 
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31's
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Joined: Mon Mar 05, 2007 5:33 pm
Posts: 191
Location: West Milford, New Jersey
so i re-bleeded the master cylander but i cant seem to get the foward chamber to bleed(this is the rear brakes i beleive... correct me if im wrong) the rear chamber will blead fine. any thoughts on why this mignt be happening would be help full

_________________
1994 Jimmy, bullet proof 4L60E, Posi-Lock, Cooper Discoverer STT's, 55w Hella 500's, Camoclad Camo, Magnaflow Cat, Dynomax catback exaust, mostly stock but still takes a beating


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