Parking Brake Warning Light/Alarm Stays On (Freightliner 2007)

[kapa]

I have a 2007 Freightliner skoolie (Mercedes engine and Allison transmission).
My Parking Brake Light stays on and the alarm will go off once the bus starts to move.
The air pressure is good, the brakes (hydrolic) do not engage and I can move freely.

The bus has been sitting for almost 2 years. Changed the Purge valve recently to get my air pressure back up, but now the buzzing alarm and the parking brake light wont go off.


The only symptom that I can notice is that it takes a bit of more effort to get the bus stopped, but its been sitting for almost 2 years so I take that as pretty normal the brakes are a bit stiff.


What can I check?



Please help!
Thank you!

[kapa]

Hey guys, I am still having this issue. If anyone knows to direct me a bit to a direction that helps me to find the problem, would be much appreciated!

[kapa]

I've heard it could be a bad ground wire of the brake switch(or the brake switch itself) that usually gets rusty and breaks, but haven't found anything yet.
I can hear the brake switch making a click sound once pressed so I think it's all good.
Or could it be still that?

[bluebird90]

We need more info on the type of brake system you have. Air and hydraulic? Do you have an air over hydraiulic system? ( very bad when you loose air). More details. even pics.

[kapa]

Hey bluebird90!
Thanks for replying!
I did say hydrolic, but, yes, I really meant hydraulic.

If I have an air over hydraulic system?
How can I check that?

I did lose air before. The bus rear end was squatting down, and bus sit like this for a while. I ended up changing the purge valve and after that no problems with air building up and maintaining it. But only the parking brake light is now on with the annoying alarm.

The only thing that I know that works on air is the ride suspensions, but as I stated, everything seems to work now as it should. The ride height is normal, brakes are working, bus is rolling.

I can give you as much details as necessary, and even do pics and videos. Just need to know what I am looking for

Thank you for your help, really!!!

[bluebird90]

My guess is you have full hydraulics for brakes and air for accessories. your power brake comes from a hydroboost system thats driven by the power steering pump . Its that hydro looking thingy that the master is attached to. there are several switches there and an electric motor that powers the hydroboost when the pump isnt running. your problem is probly there.

[kapa]

Thank you so much for helpin, bluebird!


Am I looking at the right place?
If so, what should I really focus on there? The switches?

[bluebird90]

Yup. you're in the right place. that thing between the master and firewall is the hydro unit. look for bad connections or sensors. Does the hydro motor operate when you apply the brakes, engine off?

[kapa]

Yes it does, the el. motor works.
And so far all the connections seem alright to me.

[kapa]

Problem found and solved.
Braking fluid was below the minimum (No min-max level so it was hard to see). Noticed some brake lines were rusted and leaking so ended up replacing them.


Now a new issue. Whats the best way to bleed the brakes? Or to get the air out from the lines?
I am reading from another post that its not as easy as it sounds, due to hydro pump I guess?