With engine running pedal slowly goes to the floor

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

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

CHERRY PICKER

MEMBER
5 POSTS

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

KEN L

MASTER CERTIFIED MECHANIC
47,513 POSTS

NSF pipes? Are those the flex lines or?

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Thursday, April 4th, 2019 AT 11:55 AM

CHERRY PICKER

MEMBER
5 POSTS

Hi, yes they are flexible pipes.

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Friday, April 5th, 2019 AT 9:11 AM

KEN L

MASTER CERTIFIED MECHANIC
47,513 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.