Brake Pedal Issues on 2004 5.9 Cummins 2500 – Soft Pedal & Slow Return

[Ruben_Nor]

Hello!

First post on here

I bought a 2004 5.9 Cummins 2500 about a week ago. The brake pedal is acting weird. Sometimes, it's hard at the beginning right after I start the engine and press it in, but only for a split second. Then, when I press it again, it goes soft (almost falls to the floor). After that, it becomes firm again at the end, and the brakes work fine (they stop the car well, so to say), but the pedal remains soft until nearly the end.

The pedal also struggles to return all the way out. When I stop the car and get out, I have to pull the pedal back out manually to prevent the brake lights from staying on.

Has anyone experienced this before? Is it just air in the system, or is the master cylinder faulty?

The previous owner replaced the rear calipers and changed the front pads. It also passed the Norwegian road test, which is similar to the US DOT inspection.

 

[Ruben_Nor]

A lot of this issue seems to be related to the master cylinder now that I've been reading my Haynes manual a bit more thoroughly. I doubt it's air and believe that the master cylinder has gone bad, as there is no leaks to be seen.

 

[jws123]

well its a 2004 due for a master cylinder to fail if you didnt blow any lines most likely your issue.

 

[Ermio]

Hello!

First post on here

I bought a 2004 5.9 Cummins 2500 about a week ago. The brake pedal is acting weird. Sometimes, it's hard at the beginning right after I start the engine and press it in, but only for a split second. Then, when I press it again, it goes soft (almost falls to the floor). After that, it becomes firm again at the end, and the brakes work fine (they stop the car well, so to say), but the pedal remains soft until nearly the end.

The pedal also struggles to return all the way out. When I stop the car and get out, I have to pull the pedal back out manually to prevent the brake lights from staying on.

Has anyone experienced this before? Is it just air in the system, or is the master cylinder faulty?

The previous owner replaced the rear calipers and changed the front pads. It also passed the Norwegian road test, which is similar to the US DOT inspection.

You have a common problem before you spend a lot of money and effort in replacing the master replace the front rubber hoses to the wheel calipers when they get old they have a tendency to collapse ware they are connected to the frame when you press the brake the pressure overcomes the collapse but when you release the collapse prevents the fluid returning to the reservoir and keep the breaks engaged it will eventually release and the break will fell normal biut will do it again it also may thruogh you in a direction depending on witch hose bad . Ake me how I know this

 

[Ruben_Nor]

You have a common problem before you spend a lot of money and effort in replacing the master replace the front rubber hoses to the wheel calipers when they get old they have a tendency to collapse ware they are connected to the frame when you press the brake the pressure overcomes the collapse but when you release the collapse prevents the fluid returning to the reservoir and keep the breaks engaged it will eventually release and the break will fell normal biut will do it again it also may thruogh you in a direction depending on witch hose bad . Ake me how I know this

They have been replaced by the previous owner. Master cylinder arrives this week from the US, we will soon find out

 

[Ruben_Nor]

Got around to replace the master cylinder this weekend. Now the pedal works like a brand new car! I plugged the break lines that connect to the master cylinder so that i wouldent get air in to the ABS module and that worked fine. The whole swap took mabe 30 minutes including bench bleeding the new master cylinder.