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Brake pedal going to the floor


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Hello all.

 

I bought my Journey few months ago and it arrived time for it to go for check (M.O.T. periodic check) and it failed on brakes.

As I'm diy weekend warrior and have worked on cars for a few years now (and beleiving it's a simple task as usual) I approached the task myself.

In the end there was no leaks or other big problems seen at this point.

Well new dinner plates and squeeker-stopper (discs and pads), rear caliper and rubber lines from body to the rear control arms, renewed sliding pins (replaced or re-greased where needed), bleeding manually (one way valve method and vacuum afterwards due to leaky threads on bleeding valves), all 4 corners beed done.

Bleeded the abs with the computer and now I'm facing the brake pedal that works but after fully stopping the vehicle and still holding the brake pedal, it will sink.

No dash emojis (warning lights) no error codes. Ok... So I went for re-check, plugged there into the pressure machinhe and bleed it again with the mechanic same with abs unit.

 

Guess what... No luck.

 

Also worth mentioning if the car is shut down the pedal will stay firm in place and won't sink.

 

So anyway we thinked about abs unit being faulty (hydraulic unit) or master cylinder, both changed, bleed (over 3 Liters of fluid), started to see many bubbles in the front right corner bleeder, unlike 3 other corners, bought rubber lines front, changed them, all works but the sinking still remains.

The front left caliper looks newish, left rear is new, got the both for right side but can't see problems with old ones, also I know about the chemical reaction between the caliper and DOT3 liquid and the rubber lines deterioration causing clogging (rubber line front right where the bubbling occoured is changed to new one) caliper look to be working alright.

So a bit unsure what else can be, some clues about specific ATE brake system in the Journey?

 

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Your info states EU for location. What Engine does yours have, as you have a few over there that we in NA don't get.

Sinking pedal on holding applied could be a bad booster or check valve in the vacuum line to it.

 Sounds like otherwise you have been pretty thorough in your repair process.

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1 hour ago, marek196c said:

Hi, yes sorry it's 2.0 vw diesel (140hp) with mps6 (powershift) auto gearbox.

 

In terms of vacuum booster, why do you think is the culprit?

On other forums for Dodge vehicles that I have participated on with the same motor{ I suspected you had the Diesel}they have reported a check valve in the booster vacuum line going bad. This causes the sinking pedal due to vacuum sucking hard against the rear seal of the master cylinder, which gives the impression of a faulty master cylinder.

 We don't get the VW 2.0 motor here in the NA market, so I can't give you much more info. You may want to try a VW dealer or specialist shop, the brake boost system is probably the same.

Good Luck to you and let us know how you end up fixing this problem.

Edited by 5rebel9
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  • 2 weeks later...

Hey, few weeks ago checked for the valve and it's working fine, tried to swap with one from jeep compass to see if there are some differences in behaviour but no luck, now I'm hunting for the vacuum booster but difficult to find it (living in Norway be like this sadly), if someone knows other vacuum boosters that fit from other models? Found few with P04...75af ending instead of P04...74ai but unsure if there are some differences in amount of force they produce. Attached file with part number.

IMG_20240618_181751.jpg

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  • 2 weeks later...
On 6/27/2024 at 7:51 PM, Dean H said:

This is for 2016 2.0 diesel 

vacuum brake booster.

IMG_20240626_045857.thumb.jpg.695ba3532ba8bfd6725226c135faccdd.jpg

IMG_20240626_045929.thumb.jpg.1479764042926bbb922a8cb863b513f7.jpg

IMG_20240626_050010.thumb.jpg.c85852570740f8f8c9274e25b623a7de.jpg

IMG_20240626_050102.thumb.jpg.3d7c2c1056e20e669efff3750a859b73.jpg

All tests passed however 1st test 4th step I got the desidered action on starting engine and brake pedal falling down, problem is it's not stopping but going all the way to the floor basically. While it should stop after some (minor) brake pedal.

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