I have a 1995 GMC Jimmy and I have bled the brakes but their is still air in the

[cassita]

line.? Also the cylinder bubbles and I need some advice on how to fix this problem Thanks

 

[Molson02536]

line.? Also the cylinder bubbles and I need some advice on how to fix this problem Thanks

I looked at my Alldata for my blazer about the bleeding procedure, they say there's some bolts on the sides of my EHCU (ABS module) under the hood that you are supposed to crack open and use somekind of special tool to bleed it out (3 of them) somekind of combination valve pressure bleeding valve or some mess... and it's not the 2 bleeders on the top of the unit, here's the proceedure they have down for 95+ Jimmy's/Blazer 4wd.

You can bleed the master cylinder, lines, calipers, wheel cylinders and never get the air out of the system,. You must follow a special procedure to bleed the EHCU, but only if your EHCU is good! If the EHCU has air in it, you can push 100 gallons of brake fluid through the rest of the system and never get allair out.

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.

 

[sofasurfer]

Aha!! Someone with the same trouble as me.
95 sierra. 4x4.
I had my brakes bled 4 times last year. Also replaced master cylinder and wheel cylinders. Brakes still feel like they need bleeding. I can hit them hard and they feel hard but after a split second the pedal goes soft. This causes a delay in the braking action and when they do finally grab it is a poor grab.
Does this sound the same as Cassita's problem.

This is the first time I have heard of the problem you discribe as being related to the EHCU. In fact I just discovered the EHCU a little while ago.

I will read your proceedure better this evening. I have NO knowledge of the EHCU. Just more confusion.

I was thinking my problem was the rubber brake hoses getting weak. Possible?
Steel brake lines corroding and causing obstructions?

I read that the brake system also produces trouble codes. Is this true? How do I check for the codes?

Thanks.