Can't unlock my parking brake!

[Jolly Roger bus 223]

i wouldnt have thought that a 2005-07 bus would have air over hydraulic brakes?
i thought that was phased out in the late 80's early 90's.

[dbsoundman]

They’re not air over hydraulic, they’re just air brakes.

[Dbacks2k4]

Originally Posted by Jolly Roger bus 223

i wouldnt have thought that a 2005-07 bus would have air over hydraulic brakes?
i thought that was phased out in the late 80's early 90's.

I've seen some IC buses of this generation with hydraulics service brakea and air parking brakes. Thought the hydraulic system was air over hydraulic from what I'd read, but I could be wrong. My whole fleet is full air brake so no first hand knowledge. I like my buses to stop if the brakes fail

[rossvtaylor]

Originally Posted by dbsoundman

They’re not air over hydraulic, they’re just air brakes.

I'm with you on this. The yellow diamond button is telling.

My guess is that this is pretty simple and related to some of the interlock wiring the OP disconnected. But that's just a guess.

[Dbacks2k4]

Originally Posted by rossvtaylor

I'm with you on this. The yellow diamond button is telling.

My guess is that this is pretty simple and related to some of the interlock wiring the OP disconnected. But that's just a guess.

Possible but on all my ICs of this generation if the interlock is triggered it prevents the engine from starting, not from disengaging the parking brake. Definitely worth checking out though!!

[Shortbus PA]

What do you think I could have disconnected that would have triggered the parking brake? Do you think disconnecting the ceiling escape hatch could have done it ... that's the thing I did prior to the parking brake not engaging and the brake pressure warning light coming on.

[rossvtaylor]

Originally Posted by Dbacks2k4

Possible but on all my ICs of this generation if the interlock is triggered it prevents the engine from starting, not from disengaging the parking brake. Definitely worth checking out though!!

And that's definitely a possibility...and I'm no authority on these buses. I think a key piece of info I haven't seen is what the air pressure gauge/s read. Did I miss that?

[Shortbus PA]

There's no air pressure gauge on my dashboard anywhere, so I can't tell. Makes me think it's only hydraulic, right?

[rossvtaylor]

Hey Shortbus, it looks like you're not alone. Someone just posted this in the FB school bus group. I've found that the level of expertise and viable help is much higher here on Skoolie.net...but I'll watch that and let you know if I see any genius there.

[Shortbus PA]

Great, thanks ... I'm glad I'm not alone in this problem!

[rossvtaylor]

Originally Posted by Shortbus PA

Great, thanks ... I'm glad I'm not alone in this problem!

Can we back up and get a bit more info, so we can better help? Can you post a photo of the yellow brake release button you mentioned? And you said you have a brake pressure warning light...can you post a pic of that, too, and perhaps your entire dash area and gauges? You said there's no identifiable air pressure gauge, but I've seen some buses where they have vague/dim and not well marked indicator lights (like a bar graph of green and red squares) below the speedometer. From what I'm reading, it sure sounds like you have air brakes. If you can take a photo of your rear axle, near the inside of a rear wheel, that would be great too! Knowing what system you have, for sure, will definitely help troubleshoot it.

[BarnYardCamp]

Since the OP stated he has an audible alarm sounding..(could be low air alarm), or could it be related to the H-cap door? The OP said he disconnected some of the wiring to the E-hatches, is he sure the wires were E-hatch and not to the H-cap door, causing the bus to "think" the H-cap door is open. Could that cause the brake to stay engaged?

[Shortbus PA]

Can't seem to post pictures ... how do I do this?

[Shortbus PA]

Just downloaded and read the manual for my model ... it's definitely a hydraulic brake system and my problem seems to be with an interlock system that keeps the parking brake on. The manual references the wheelchair lift in the interlock system, but I drove the bus home from the salvage yard after jettisoning my lift so that's a bit strange. However, when I removed the single escape hatch (this involved disconnecting a single plastic click-together mechanism from the two wires on the hatch) the parking brake remains locked. Unfortunately, I tossed the escape hatch, so I can't plug it back in and see if that releases the brake.

Any ideas on how to address the interlock issue?

[Shortbus PA]

Oh ... I'll add that my dash shows a brake pressure warning light, the ABS light is lit, the Park (P) light, as well as a "Service (P)" light.

If I can ever figure out what I'm not getting photos to attach I'll post pics.

[Shortbus PA]

Here's my dashboard

[wrenchman64]

You have hydraulic brakes. and air parking brake. you must put your foot on the brake pedal to release the parking brake. you say there was a wheel chair lift in the bus at one time. if the power switch on the switch panel is on the parking brake will not disengage.

[Mekanic]

Our latest buses that have full air brakes will not release the park brake with out your foot firmly on the brake pedal AND will dump air pressure if you don’t do it this way.

[Shortbus PA]

Yeah, it's not an issue of my trying to release the parking brake without having my foot on the brake pedal.

There's no switch open the panel for the wheelchair lift, that was operated by a switch on the lift itself.

I removed the lift about six months ago and have driven the bus without a parking brake problem. The problem with the parking brake began after I removed the ceiling escape hatch and disconnected the wire that ran to it.

So, my best guess is that there's a interlock system. As I said in my original post, I've got a beeping noise now after having removed the hatch ... and the brake pressure warning light is on.

So ... I'm looking for ideas on how to rectify the interlock problem.

[Reanbush]

Sounds like your parking brake is locked up. Easiest way to get it moving is to cut the cable that goes to parking brake. They had issues with this system. It’s basically electric to hydraulic to cable. Chock wheels good and have someone hold the brake and cut the cable to parking brake. Then you can get it in somewhere to get repaired. You will not have a parking brake after though. Ours shorted out once and locked up on the rd, I carry some snips with me just for that reason. At least I can get it somewhere then.