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  #1  
Old 12-01-2008, 11:42 PM
 
Join Date: Dec 2008
Posts: 5
joshbuchan is an unknown quantity at this point
Default can't bleed all air outta brakes

Hello chev pros [sm=hail.gif] Are GMC trucks OK to ask about on here? This site seems a lot more active than the others I found. I have a 96 V6 Jimmy 4x4 with the worst brakes ever!! and desperately need some help!!!

Let me start off saying I absolutely HATE ABS!!!!!! has to be the worst feeling not having control of your own brakes. The pedal is super soft and goes to the floor and if it is raining out and I try and stop at a light the ABS activates and makes the craziest noises, then I blow through the red light [:@]. I have stopped driving it until I get it fixed.

First thought was air in the lines, so tried bleeding them. No matter how much I tried I still got big air bubbles out of the drivers rear. I replaced the cyls (DR was a little wet under the boot) and now I don't get the big bubbles out back. BUT now the fronts (replaced the pads while up on jacks) it looks like a milkshake coming out of the calipers when I bleed, fluid looks like pure teeny bubbles (using a clear 1/4" chunk of rubber tube) .
I have tried all different styles I know of bleeding, no change.
I forgot to put the master cyl cap back on one time after topping up and my helper just barely touched the brake pedal and a 10" fountain of fluid shot out of the master cly (I think from the rear chamber) IS THIS NORMAL??
The fluid after a round of bleeding is all frothy looking in the rear chamber of the master cyl..........DOESN'T SEEM RIGHT TO ME
I wondered if something funky was going on in the ABS module thing so I tried bleeding with the truck running to give the sensors power......no change.
When I first started this marathon bleeding the fluid was black so I sponged the fluid out of the master reservior and wiped it out, started with new silicone fluid.
The ABS light has never come on when truck is running, just when ignition gets turned on and all the lights flash on and off.
The parking brake light comes on sometimes while braking and sometimes stays on for a while.

Do I have a duffed master cylinder or ABS Module or some other problem?? Thing that has me baffled is it's like there is a leak sucking in air but not leaking fluid out???
Please let me know if you need any more info.

PLEASE HELP BEFORE THIS TRUCK GETS A BRICK ON THE GAS PEDAL AND LAUNCHED OFF A CLIFF!!!!!!!!!!!

Thanks a bunch Josh

  #2  
Old 12-03-2008, 08:31 AM
 
Join Date: Dec 2008
Posts: 5
joshbuchan is an unknown quantity at this point
Default RE: can't bleed all air outta brakes

Bump......anyone help with this issue?? truck is sitting in my driveway up on stands and I need it!!!
  #3  
Old 12-03-2008, 12:41 PM
 
Join Date: Nov 2007
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N2BLAZIN is an unknown quantity at this point
Default RE: can't bleed all air outta brakes

you let the master go dry and now in order to get the bubbles out you will have to bleed the master by itself then hook the lines back up and bleed the system starting with the pass rear. Inspect the ABS unit closely for leaks. It sounds like an air pocket in one of the ABS solenoid units and its wreaking havoc on your whole system.
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  #4  
Old 12-03-2008, 01:54 PM
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Default RE: can't bleed all air outta brakes

Welcome to the wonderful world of ABS brakes.The ABS brake failures androll-over accidents is what madethe S and T-Series GM vehicles a deathtrap. I have been grappling with the exact same problems for two months. I will tell you what I have determined:

DO NOT use silicone brake fluid with ABS brakes. Only use DOT 3. Silicone brake fluidcan damage the ABS controller.

I have determined that my Electro-Hydraulic Control Unit(ABS modulator or controller) is bad. The fluid has never been changed. Particles of wornseals in the EHCU,rust and dirty fluidhas deterioratedthe dump valves in the EHCU. The dump valves aresometimes not closing completely when I apply the brakesandfluid is by-passingthe dump valvesinto the low pressure accumulators. That will allowthepedalfall to the floor unexpectedly. The condition appears exactly the same as a bad master cylinder which is the first thing I replaced and it did no good at all. A by-passing dump valve in the EHCU will not settrouble codes and will not turn on the orange ABS warning lightin the instrument cluster! The red brake warning light(not ABS) will turn on if activated by low fluid or a by-passing master cylinder. Thatwarning lightiscontrolled by the combination valve switch.My conbination valve is good and is functioning correctly.

A rebuilt1990-1992 S-T-Series 4-wheel sensor EHCUcosts about $850. There are sources on e-bay that offer rebuilt1996 and later controllers. My 1991 S10 Blazer 4x4 with 4WAL brakes is a Kelsey-Hayes EBC4 controller. Only the1990-1995 4WAL brakes on S and T 10 series used the troublesome EBC4 controller.Your 1996 S/T-10 Jimmy/Blazer uses a EBC310 (GM) controller and Ford used the same one. Those units were aneededimprovement over the EBC4 controller but they still had similar problems. GMducked a expensive recall of the EBC4 controllers because most of the failures were due to old and dirty fluidwhich GM blamed oncustomer neglect. Besides, most of theEBC4 failuresdid not occur until the vehicle was well out of warranty. During a NHTSB investigation of a few thousand accidents due to the pedal going to the floor, GM made the lame excuse in front of Congress that it wasthe fault of the driver not knowing how to use ABS brakes!Of course the congressmen fell for it. GM recalled many1996 and later S/T series vehiclesequipped with the EBC310controllersbut they blamed those recalls on a$104WD selector switchassembly, not a $850 controller.

You can bleed the master cylinder, lines, calipers, wheel cylindersuntil hell freezes over and never get the air out of the system,. You must follow a special procedure to bleed the EHCU, but only if yourEHCU is good! If the EHCU has air in it, you can push 100 gallons of brake fluid through the rest of the sytemand never get allair out. I cannot tell you how to bleed the EBC310 controller becuse all I know is how tobleed the 1990-1995 EBC4 EHCU. The 1990-1992 EBC4 controllers are four sensor (each wheel) units and the 1993-1995 EBC4 controllers are 3-sensor (2 front brakes and 1 driveshaft) controllers, with different ECM programming, otherwise they are the same. It is not a difficult job to bleed the EHCU, in fact it iseasier than bleeding thecalipers and wheel cylinders.

Don't feel bad about not nowing this because there are no independent repair shops and three Chevrolet dealerships in my area and all have"ASE Certified" techniciansand those guys did not know how to bleed mine . That is not because the ASE Certified technicians arestupid but it is because they don't have a Scan 1 tool and the timeto work on a 18 year old Chevrolet, not even at $90 per hour. The GM dealer-"shafts" are too busy with make-ready and warranty work on the thenew junk cars they are trying to sell.

An independent study byThe Institute for Highway Safety determined that ABSbrakes have not reduced the number or cost ofaccidents. Don'tblame the American automakers.....they were just trying to comply with stupidgovernment mandates. The U.S. Governemntshould GIVE (not loan) the American automakers 100 billion dollars because government agencies such as theEPA and NTSB arethe main reasonthe car makers are going broke!
  #5  
Old 12-03-2008, 02:22 PM
 
Join Date: Dec 2008
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joshbuchan is an unknown quantity at this point
Default RE: can't bleed all air outta brakes

thank you both for your responses........N2 BLAZIN, I haven't let the MC run dry but I can't speak for the previous owner (brakes weren't great when I bought it)
Duntov, that shed a lot of light on the mysterious ABS-BS thank-you for taking the time to explain! I noticed 2 bleeder nipples on the ABS block. Do you think that bleeding it will help of are is it toasted?
Is it possible to by-pass the abs crap and just run the lines straight off the master cyl to the front&rear like old school?? Like I said I like being in control of my brakes not some malfunctioning computer thinking it knows when and how I need to stop[sm=badidea.gif]
  #6  
Old 12-04-2008, 09:53 PM
 
Join Date: Dec 2008
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joshbuchan is an unknown quantity at this point
Default RE: can't bleed all air outta brakes

back up top...

Can anyone see any problems with unhooking the ABS module and running the lines from the calipers and drums straight into the master cylinder??? like any older truck
Will this mess with any other functions of the computer ie: 4x4 ??
  #7  
Old 12-05-2008, 05:59 AM
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Default RE: can't bleed all air outta brakes

I have considered by-passing the EHCU. I have read it can be done on some vehicles and I have also read it cannot be done on others without relpacing theelecronics and braking system with one from a vehicle without ABS.As far as a 1990 - 1992S10 Blazer with a EBC4 four-wheel anti-lock brakesconcerned, by-passing the ABS isnot anoption.

The only thing I have not done when bleeding the EHCUis to disconnect the battery during the bleeding process. Since I feel like my EHCU is bad anyway, that would not have done any good. However, when I install the rebuilt EHCU, I will disconnect the battery to deactivate the electrical components in the EHCUand keep the batterydisconnected during thebleeding process. That may be the only way to completely purge the air from the EHCU. It is at least worth a try.
  #8  
Old 12-05-2008, 09:41 AM
 
Join Date: Dec 2008
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joshbuchan is an unknown quantity at this point
Default RE: can't bleed all air outta brakes

where can I find instructions to bleed the EHCU? I have read that you need a scan tool to do it.....why is that?

anyone have a link to a step by step? my haynes manual has nothing on the proceedure
  #9  
Old 12-05-2008, 10:49 AM
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Default RE: can't bleed all air outta brakes

I found a good description of the EBC4 ABS unit bleeding procedure at www.autozone.com Click on: Repair Info; Repair Guide; Brakes; Four Wheel Anti-Lock 4wal System 1983 - 1993 GM Blazer/Jimmy/Typhoon/Bravada. If you are bleeding by foot pressure, be paitient and don't give up becauseit takes a long time to push the air out of the ABS EHCU. It may take as many as15 to 20 separate attempts to get a firm pedal. A pressure bleeder is what you need for this type system.

I bled my EHCU according to the instructions on theAutoZone website and had good brakes for about 50 miles then they got soft and the peal would go to the floor. I am am convinced that if my 18 year old EHCU was good at the time, I would have good brakes now. That is why I pruchased a rebuilt EHCU for $700. Autozone has Cardone rebuiltEHCUadvertised but they don't have any in stock and cannot get any because Cardone is out of cores and do not expect to get any more. I purchased arebuilt Raybestos EHCU and it was one of the last 10 units they had.Rock Auto Parts recently dropped the Raybestos EHCU from their on-line inventory. Rock Auto Partsstill has the rebuilt Cardone EHCU advertised but they are not aware thatCardone is not offering them anymore. I talked to a Cardone represenative about this matter. Raybestos and Cardone are the only companies that rebuilt those EHCU.

You must usethree OTC-7853 depressor tools to bleed the system.Placing duct tape over the vales does not work. When using the depressortoolson the two low pressure accumulator valves and the rear (proportioning section) of the combination valve,DO NOT turn the wing nut down but finger tight or no more than .030" when depressing the valves.Remove the rubber boots on the two EHCU accumulator valve stems and attach the tools.The combination valve stem doesnot have a rubber boot.The proportioning valve stem on the combination valve islocated on the opposite end from the rear brake line attached to the combination valve that goes to the EHCU .The OTC 7853 depressortools are available at www.carparts.com for $5.00 each. The same tool isas much as $30 each from other suppliers on the internet.

Those are the tools thatthe so-called "ASE Certified" technicians DO NOT have and that is why they do not know how to bleed these type ABS brakes. They do not want to pay $15 for three tools that they would never used but once every ten years or so. A technician at a large Chevroletdealership told me that! I hope that ASE Certified Technicianis laid offin a few months afterGM goes broke then hemay be able to get a jobas a fry cook at McDonalds.
Old 12-05-2008, 10:49 AM
 
 
 
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1996, 4wal, abs, blazer, bleed, bleeding, brakes, cost, dealer, ebc310, ehcu, gm, hayes, kelsey, kelseyhayes


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