- Joined
- Jun 25, 2019
- Messages
- 7
- Reaction score
- 3
- Location
- Connecticut, USA
- VCDS Serial number
- C?ID=195067
I have a 1J Mk4 GTI 1.8T AWP with ASR (no ESP) with a lot of odd brake problems that i'm very deep into with time money and effort.Most of them i've "solved." (I think. I haven't gotten to road test the car much) There is one I have yet to figure out:
Symptoms: When I open the rear brake caliper bleed screws and pump the brakes, no fluid comes out and the pedal feels hard. This has changed over time from not being able to bleed one rear caliper to now being unable to bleed both rear calipers.
Solutions: New soft lines for all four corners. New hard lines going from the ABS unit to the rear soft lines. New bleeder screws. Took rear calipers off and tested flow from line entry to bleed screw with compressed air (caliper flowing correctly). Cycled ABS pump with VCDS block 03->output tests. Went through procedural steps. Took ABS unit off and blew air through ports, everything flowed symetrically and without issue. Purchase low mileage ABS unit and install both the module and fluid block. Cycle ABS with VCDS block 03->output tests again. Unplug battery and ABS unit plug (Resets ABS?) Remove lines going from master cylinder to ABS fluid block, blow through with compressed air (lines flowing correctly). Reinstall lines, pump brake pedal to test master cylinder flow (fluid comes out in bursts from both lines, seemingly sucking air in when pedal reaches the bottom of its stroke).
Recently replaced parts: New calipers, all four corners. New brake pedal switch. front right new ABS ring. New rear hubs/ABS rings. New ABS sensors all 4 corners.
I'm unsure of what proper master cylinder fluid flow looks like and what improper master cylinder fluid flow looks like. I'm unsure of how to test a master cylinder for correct operation. A few friends have advised replacement of the master cylinder and doing a bench bleed of the new unit. This is the last option and if this does not solve the issue, I'm unsure of what to do next. AS of now, I can only bleed the front calipers successfully.
Any alternative solution ideas or further understanding of how the ABS/brake system operates either electrically or hydro-mechanically would be greatly appreciated.
Symptoms: When I open the rear brake caliper bleed screws and pump the brakes, no fluid comes out and the pedal feels hard. This has changed over time from not being able to bleed one rear caliper to now being unable to bleed both rear calipers.
Solutions: New soft lines for all four corners. New hard lines going from the ABS unit to the rear soft lines. New bleeder screws. Took rear calipers off and tested flow from line entry to bleed screw with compressed air (caliper flowing correctly). Cycled ABS pump with VCDS block 03->output tests. Went through procedural steps. Took ABS unit off and blew air through ports, everything flowed symetrically and without issue. Purchase low mileage ABS unit and install both the module and fluid block. Cycle ABS with VCDS block 03->output tests again. Unplug battery and ABS unit plug (Resets ABS?) Remove lines going from master cylinder to ABS fluid block, blow through with compressed air (lines flowing correctly). Reinstall lines, pump brake pedal to test master cylinder flow (fluid comes out in bursts from both lines, seemingly sucking air in when pedal reaches the bottom of its stroke).
Recently replaced parts: New calipers, all four corners. New brake pedal switch. front right new ABS ring. New rear hubs/ABS rings. New ABS sensors all 4 corners.
I'm unsure of what proper master cylinder fluid flow looks like and what improper master cylinder fluid flow looks like. I'm unsure of how to test a master cylinder for correct operation. A few friends have advised replacement of the master cylinder and doing a bench bleed of the new unit. This is the last option and if this does not solve the issue, I'm unsure of what to do next. AS of now, I can only bleed the front calipers successfully.
Any alternative solution ideas or further understanding of how the ABS/brake system operates either electrically or hydro-mechanically would be greatly appreciated.
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