persistent
TYF Newbie
- Joined
- Nov 10, 2023
- Posts
- 8
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- 14
the wife's 2020 tahoe recently had a pretty bad brake failure: the front drivers caliper slide pin bolt came loose, caliper rotated up, piston pushed itself out, brake fluid all over. i took the caliper off, removed dust boot, reseated piston, and reinstalled caliper. after putting everything back together, i did a normal pressure bleed with a motive hand pump bleeder, but it took a bit of fiddling to get it to start bleeding properly. when starting the bleed at the rear passenger caliper, i got really poor flow. i moved to rear drivers caliper, got good flow, moved back to rear passenger caliper and got good flow there. i bled the front calipers without event. after completing the normal pressure bleed, the brake pedal was still spongy.
after searching the forum, i found several suggestions that the next thing to try was an abs automated bleed since there can be air trapped in the abs system. i confirmed this as a good next thing to try in the service manual, which cites the abs automated bleed as being appropriate when an "extreme loss of brake fluid has occurred" or "base brake bleeding does not achieve the desired pedal height or feel".
i went ahead and did the automated bleed using a low cost scan tool (cgsulit sc530), and it assumed i was doing a pressure bleed, which worked out because i had the equipment handy. this process can be done easily by a single person, despite my having my wife present for this first run. the spongy brake pedal has firmed up nicely and is working as expected.
considering that a normal bleed isn't much less work than an automated one, and that the abs automated bleed also purges the secondary brake fluid circuits, does it make sense to just do this every time you bleed the brakes? i'm unsure why the service manual suggests doing a normal bleed before an abs automated bleed, that would be nice to know. is there a well-defined set of circumstances where you should run the abs automated bleed versus just a normal bleed?
i used a pretty crappy scan tool, but it got the job done. i guess i should inquire about scan tools in a separate post.
after searching the forum, i found several suggestions that the next thing to try was an abs automated bleed since there can be air trapped in the abs system. i confirmed this as a good next thing to try in the service manual, which cites the abs automated bleed as being appropriate when an "extreme loss of brake fluid has occurred" or "base brake bleeding does not achieve the desired pedal height or feel".
i went ahead and did the automated bleed using a low cost scan tool (cgsulit sc530), and it assumed i was doing a pressure bleed, which worked out because i had the equipment handy. this process can be done easily by a single person, despite my having my wife present for this first run. the spongy brake pedal has firmed up nicely and is working as expected.
considering that a normal bleed isn't much less work than an automated one, and that the abs automated bleed also purges the secondary brake fluid circuits, does it make sense to just do this every time you bleed the brakes? i'm unsure why the service manual suggests doing a normal bleed before an abs automated bleed, that would be nice to know. is there a well-defined set of circumstances where you should run the abs automated bleed versus just a normal bleed?
i used a pretty crappy scan tool, but it got the job done. i guess i should inquire about scan tools in a separate post.
