Brake pedal goes to the floor

CRB94

MEMBER
2010 DODGE RAM
5.7L
V8
4WD
AUTOMATIC
220,000 MILES

Truck listed above is a 1500. CV axles, hubs, brake calipers, rotors, and pads. Bled brakes via proper procedure multiple times. Pedal is firm when truck is off. As soon as I start it up I lose all brake pressure. All ABS and brake lights (including traction and ESP) are on. Used my scan tool to do an auto bleed on the ABS. No luck.

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

The idea that it goes to the floor is usually related to a faulty master cylinder. Take a look through this link:

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

If there are no leaks, no air in the system, and everything is sealed, this is my first suspect.

Keep in mind, when you start the engine, you get assist to the brakes which makes it much easier to press. Try this: With the engine off, hold pressure on the brake pedal. See if it slowly goes to the floor.

Let me know.

Joe

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Saturday, September 18th, 2021 AT 9:10 PM

CRB94

MEMBER
2 POSTS

Thank you for your response. When the truck is off the pedal holds firm, zero signs of leaks or seal issues. Personally, I'm leaning toward a faulty ABS module. I've had random low circuit codes with the module in the past. I'm new to Mopar, therefore I don't know how much they differ from GM. But when I did previous auto bleeds on GM modules, there was a distinct whining sound when the module began to bleed. When I bled this current module, there was no sound. Perhaps a coms issue that my scan tool overlooked? Seems to me that the module has quit on me. If that's not the problem then I'm stumped. Any other insight would be greatly appreciated.

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Sunday, September 19th, 2021 AT 12:10 PM

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

There could be an issue with the module. You should have heard it actuating. You indicated there were low voltage codes. Do you remember what they were? I can do a little research and get diagnostics specific to a code.

Let me know. Hang in there, we'll get it figured out one way or another.

Take care,

Joe

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Sunday, September 19th, 2021 AT 6:03 PM