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Odd brake pressure issue non cup 172 ph2



  Clio 172 ph2 / bikes
Hi guys, just want to bounce this off someone.

Clio 172 ph2 non cup with abs.

I’m no stranger to rebuilding bike/car brakes etc, spent more time doing it than I care to think about although I’m less familiar when it comes to abs systems.

So the story,

Brakes were fine prior to this.

few months back when doing a fluid flush with a power bleeder, two callipers already done I ran into a sheared rear nipple, bled It at the rear line till I had a chance to get another caliper, not ideal but works when done right, On the last caliper I ran out of fluid in the pressure bleeder. Took a massive hit of air. So, went and got more fluid and Re bled the entire system

symptom: no matter how much I bled I got soft pedal on first pump much like you’d expect with air in the system, it’s odd as you can feel the pressure build slightly l, move as if proportioning is shifting, then there’s enough pressure to come on properly at 3/4 travel. comes in hard on the 2nd and holds pressure without dropping away.

so, rear caliper is replaced so I can properly bleed. Same symptoms persist after a day of bleeding.

take the car out, activate the abs on gravel, bleed and repeat. Marginally better after day of bleeding.

next I cave in and buy an RSTuner to do an abs bleed. Same symptoms persist after a day of abs bleeding but now the 2nd pump will put you through the windscreen.

So... I’m thinking maybe the master seals are starting to go after all the fully extended presses when bleeding ( bleeding both with and without the power bleeder, as sometimes one method will work better.)even though it’s not acting like a typically failed master.

Replaced the master, spend a day bleeding and chasing the last of the air out and ding ding ding symptoms persist.

the systems holding pressure as the pedals not falling away, there’s no leaks along the lines, the sliders all move fine, are recently cleaned and silicone greased and none of the pistons are binding.

last part of the puzzle has to be the abs pump itself. Must have a valve stuck in an incorrect phase which could also explain that odd pedal feel on the first pump where Its like I can feel transition through different pressures slightly.

Any insight of experience with similar issues would be helpful or interesting. I’m probably 30-40L if fluid down at this point.

also looking for info on matching abs pumps as every post about them is vague or misleading.

so obviously you match the number on the pump with it’s replacement, in my case 8200 270 251 in the top right corner. However, do you also need to match the Bosch ecu number underneath as well? Some say they’re coded, some say it doesn’t matter so long as it’s from the same model of car. Some say ‘match the numbers’... with zero explanation or follow up.

long read, kudos if you made it this far.
 


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