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Help Needed - Soft Brake Pedal and Wheel Bearing Play
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Posted 10/19/2019 4:48 PM
Omar510
New user


Date registered: Sep 2019
Location: SF Bay Area
Vehicle(s): 2007 G55
Posts: 4

Help Needed - Soft Brake Pedal and Wheel Bearing Play

Hey guys! I recently decided to plunge into G Wagen ownership with a 2007 G55 with approx 91k miles on the clock. I have plans to make it slightly more off road worthy with a lift and tires so i decided to start the process as parts come in.

First up was extended stainless brake and locker lines. I replaced the rear brakes lines and went to go for a flush of the lines. The drivers rear bleeder would not budge so i soaked it in penetrating oil and let it sit over night. I go to remove it the next morning and I snapped the bleeder off. My attempts to drill out the bleeder failed so I ordered a remanufactured caliper and installed it. Unfortunately I let the fluid drain out of the reservoir as a I waited for a new caliper to arrive. I spent many hours bleeding the system with a Motive Power bleeder and new fluid and just could not get a firm pedal. Feeling defeated, I took it down the road to a shop to see if they could get the air out. No luck, they recommended replacing the master cylinder so I agreed. Still no firm pedal.

The pedal takes a couple pumps to firm up. After pumping it and holding it, it will take some time but slowly sinks down. We don't see any leaks in the system.

One thing that we do notice is that the wheel bearing on the front left corner has a decent amount of play in all directions. After some searching on here, a few members have said that a soft brake pedal usually comes after a wheel bearing is worn out.

We will take care of the wheel bearing next as it is necessary but I am skeptical that will solve the braking issues because I did not have braking issues before I started this project.

I have some questions I am looking for some advice on.
1- Does the ABS unit need some special bleed procedure or will a proper pressure bleed take care of it?
2- What else am I missing that may cause a soft pedal?
3- Will a worn bearing/excessive play cause the pedal to be soft even at slower speeds?
4- Any chance the new/remanufactured caliper can cause this?
#241121
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Author
Posted 10/19/2019 7:53 PM
DUTCH
Administrator Doppelgänger




Date registered: Apr 2006
Location: US, GA, Atlanta
Vehicle(s): 2015 Audi Q7 3.0 TDI,2018 Sprinter
Posts: 9963
5000
RE: Help Needed - Soft Brake Pedal and Wheel Bearing Play

Please complete your My Profile telling us the year and model of your G, as well as where you're located. That helps to get to know and to help you better.

Thanks.
#241122 - in reply to #241121
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Author
Posted 10/20/2019 8:28 PM
Omar510
New user


Date registered: Sep 2019
Location: SF Bay Area
Vehicle(s): 2007 G55
Posts: 4

RE: Help Needed - Soft Brake Pedal and Wheel Bearing Play

DUTCH - 10/19/2019 4:53 PM

Please complete your My Profile telling us the year and model of your G, as well as where you're located. That helps to get to know and to help you better.

Thanks.
#241123 - in reply to #241122
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Author
Posted 10/22/2019 10:58 AM
J.R.
Elite Veteran




Date registered: Apr 2006
Location: Southern Maryland
Vehicle(s): 00 G500, 09 911 4S, 11 Cayenne S, 86 280GE (sold)
Posts: 828
500
Re: Help Needed - Soft Brake Pedal and Wheel Bearing Play

Search is your friend. Use advanced search: key words brake bleed; author Dutch

June 2014. pdf instructions and the most likely issue with yours.
#241125 - in reply to #241121
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Author
Posted 10/23/2019 2:50 PM
Omar510
New user


Date registered: Sep 2019
Location: SF Bay Area
Vehicle(s): 2007 G55
Posts: 4

Re: Help Needed - Soft Brake Pedal and Wheel Bearing Play

J.R. - 10/22/2019 7:58 AM

Search is your friend. Use advanced search: key words brake bleed; author Dutch

June 2014. pdf instructions and the most likely issue with yours.


My calipers only have one bleed screw each. And they have been bled according to that procedure and others as well.

I did see some of his old threads and saw Dutch had success with reverse bleeding. I have a kit that will arrive today so I will give it a shot.
#241129 - in reply to #241125
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Author
Posted 10/23/2019 6:15 PM
J.R.
Elite Veteran




Date registered: Apr 2006
Location: Southern Maryland
Vehicle(s): 00 G500, 09 911 4S, 11 Cayenne S, 86 280GE (sold)
Posts: 828
500
Re: Help Needed - Soft Brake Pedal and Wheel Bearing Play

My bet is air in the master cylinder. Once cleared, all should be good.
#241130 - in reply to #241121
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Posted 10/23/2019 9:36 PM
NHDave
Extreme Veteran




Date registered: Dec 2013
Location: Seacoast NH.
Vehicle(s): 2004 AMG
Posts: 462
300
Re: Help Needed - Soft Brake Pedal and Wheel Bearing Play

Hi Omar510
I came across this issue you're dealing with some time ago "all the brake fluid drained out of the reservoir."
Check online for a process called, Bench bleeding. You might be able to perform this process with the MC in place.
Until all air is cleared from the chambers within the master cylinder, you'll not have a good time bleeding the brake lines, like one would in a normal brake bleed situation.
Reverse bleeding might also be productive, I don't know.
#241131 - in reply to #241130
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Author
Posted 10/24/2019 6:48 AM
DUTCH
Administrator Doppelgänger




Date registered: Apr 2006
Location: US, GA, Atlanta
Vehicle(s): 2015 Audi Q7 3.0 TDI,2018 Sprinter
Posts: 9963
5000
Re: Help Needed - Soft Brake Pedal and Wheel Bearing Play

NHDave - 10/23/2019 9:36 PM

Reverse bleeding might also be productive, I don't know.


It worked for me.
#241132 - in reply to #241131
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Author
Posted 10/26/2019 12:55 AM
AlanMcR
Expert




Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3500
2000
RE: Help Needed - Soft Brake Pedal and Wheel Bearing Play

A loose front wheel bearing will definitely lead to a soft pedal.  As the wheel wobbles around it pushes the pads back.  Then, when you press on the pedal, the pads have to make up for that before they touch the disk.  Get those wheel bearings fixed ASAP.  Or, the next casualty will be the expensive CV joint in the axle ball.

I've used a pressure bleeder w/40 lbs to refill a completely empty G brake (and locker) system.  Not a problem. 

#241138 - in reply to #241121
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