Replaced Master cylinder and pedal still goes to floor HELP

Tiny
AMY LOU
  • MEMBER
  • 2006 MAZDA 6
  • 2.0L
  • 4 CYL
  • RWD
  • AUTOMATIC
  • 100,000 MILES
We replaced master cylinder, bench bleed it the whole nine yards, when we put it back on the car the pedal still goes to the floor. What could be wrong?
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Friday, July 29th, 2016 AT 8:26 PM

5 Replies

Tiny
CARADIODOC
  • EXPERT
Why did you need to replace the master cylinder? Was it to solve a low-pedal problem or did this problem just start after the master cylinder was replaced? Do you have disc or drum rear brakes? Does the car have anti-lock brakes?

Here is a guide to help us see whats going on it sounds like you have air stuck in the ABS unit

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

Please run down this guide and report back

Cheers
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Friday, July 29th, 2016 AT 8:55 PM
Tiny
AMY LOU
  • MEMBER
When bleeding the master cylinder it went dry that is why we replaced it. Disc rear brakes yes and ant-lock brakes yes. Not loosing any fluid anywhere even drove it and no loss of fluid but pedal goes to floor.
:(
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Friday, July 29th, 2016 AT 9:10 PM
Tiny
CARADIODOC
  • EXPERT
"When bleeding the master cylinder it went dry that is why we replaced it"

Why were you bleeding it? What was the original problem that started all of this?

Running the master cylinder empty is no cause to replace it unless it was damaged by running the pedal over half way to the floor. You simply refill it, and if the lines still have fluid in them, you can just stroke the pedal lightly to work the air out of the lines next to the ports. No need to bleed at the wheels.

The biggest concern at this point is you likely need a scanner to activate the valves in the ABS hydraulic controller. If that assembly has air in it, that wont bleed out of some of the chambers until the valves are opened, and that can only be done electrically.
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Friday, July 29th, 2016 AT 9:23 PM
Tiny
AMY LOU
  • MEMBER
No original problem. Replaced all the calipers and when doing that did not close one of the valves and it leaked out and dried the master cylinder.
Well I ordered another one just in case so it arrived today after eight weeks uuugghhh and have bled it, test drove it pedal is going to the floor. Thinking about real bleeding at each tire again? What kind of scanner?
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Friday, July 29th, 2016 AT 9:31 PM
Tiny
CARADIODOC
  • EXPERT
I use Chrysler's DRB3 scanner because it works on all of my vehicles, and it works on all other brands of cars starting with 1996 models, but unfortunately only emissions stuff, not brakes. The most popular aftermarket scanners are made by SnapOn, Genysis, Matco, and Vertronix. If you search on eBay for scanners, you will see there are simple code readers for less than fifty bucks, but real scanners cost thousands of dollars. Instead, check at your local auto parts stores. Many of them rent or borrow tools, and they might have a scanner that will activate ABS valves. The only alternative is to have a mechanic bleed the system.
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Saturday, July 30th, 2016 AT 12:08 AM

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