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With engine running pedal slowly goes to the floor

Tiny
CHERRY PICKER
  • MEMBER
  • 2004 NISSAN TRUCK
  • 3.0L
  • 4 CYL
  • 2WD
  • MANUAL
  • 200,000 MILES
Nissan Cabstar 2004 hard brake pedal when engine stopped. When engine running pedal goes to the floor slowly. Changed master cylinder and servo. Still no change.
Sunday, March 31st, 2019 AT 7:00 AM

8 Replies

Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello,

This sounds to me like you have a brake fluid leaks somewhere. When you have a leak in you vehicle's sealed brake system, it will not be able to build pressure and the brake pedal will slowly fade to the floor. Brake fluid acts like hydraulic fluid by building pressure and squeezing calipers together with brake pads on them. The brake pads apply friction on a rotor which is attached to the wheel stopping your vehicle.
I have included a link for you to go to down below:

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

Please go through this guide and get back to us with what you find out.

Thanks,
Alex
2CarPros
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Sunday, March 31st, 2019 AT 10:22 AM
Tiny
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After clamping off nsf brake pipes the pedal works great. No leaks, pistons working.
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Tuesday, April 2nd, 2019 AT 7:40 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,895 POSTS
NSF pipes? Are those the flex lines or?
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Thursday, April 4th, 2019 AT 11:55 AM
Tiny
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Hi, yes they are flexible pipes.
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Friday, April 5th, 2019 AT 9:11 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,895 POSTS
It sounds like you have air at one of the wheels. Can I ask if the truck has ABS brakes? Also try to block off either the front or back to see if we can isolate which end of the truck is causing issues. Let me know what happens.
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Monday, April 8th, 2019 AT 10:21 AM
Tiny
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Hi Ken, when engine is not running brake are hard when running slowly goes to the floor clamp off nsf FLEXI pipes when running brake good.
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Monday, April 8th, 2019 AT 12:36 PM
Tiny
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Ken it’s not ABS.
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Monday, April 8th, 2019 AT 12:38 PM
Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello again,

Where do the NSF pipes run to?

Thanks,
Alex
2CarPros
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Monday, April 8th, 2019 AT 3:11 PM

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