Wabco brakes blowing fuse

[Samarath]

I was coming down a mountain in Colorado and lost my brakes completely. After some searching, I found that my HCU wasn't kicking in when I hit the brakes and the 30amp fuse under the hood popped. I replaced the fuse and everything worked again, but after a short duration it blew again. Does anyone have any input?

2007 IC CE200
VT365 @215 engine
Wabco hydraulic brakes with the valve to operate the parking brake

Spent 300 at a shop for them to tell me they didn't have the software to communicate with my brakes...

[cadillackid]

hopefully its not the controller.. ive seen that controller put IC BE's out of service for months waiting on a replacement..

[Samarath]

So I guess I've been under the impression that my power steering pump would somehow offer redundancy, but after looking all around, I don't comprehend how those two systems interact. It has been a pretty harrowing experience.

[Samarath]

Is the controller the ECU?

[Rwnielsen]

Your brakes rely on a 30 amp fuse? I don't see any part of that being safe...at all.
I must not be reading this correctly

[Samarath]

Well, I have functional brakes until the fuse blows, and then I have potential catastrophe. I don't have data on my other phone or I would share the maintenance manual. If you or anyone feels like taking a look to see if I am missing something, I am grateful for all input.

Wabco HPB with the optional Power Parking Brake Supply Valve.

I think I can email the manual to anyone interested, and like I say, my ignorant self appreciates all wisdom

[Samarath]

The brakes just failed during a short move into the shade without blowing the fuse, so I am even more clueless than I thought

[flattracker]

I am surprised that hydraulic brakes could cease to function without loss of pressure. It would seem that the Federal Motor Vehicle Safety Standards (FMVSS) would require a failsafe system for the brakes, especially for a school bus.



I remember the "old Crown" came with anti-lock brakes, but they were disconnected. Of course the regular air brakes did function well.

[Samarath]

Well, the hcu motors aren't kicking in, and so I guess there technically is a loss of pressure? Or at least not a building of pressure. I think the hcu needs replacing although on schoolbusfleet.com or whatever, someone said there is a way to replace just the hydraulic motors. I really am trying to figure out how to do this on a budget...

I have checked the harness to the ECU and pins 15 and 16 have a continuity of around 50-60ohm and everything else checked out on voltage to ground with key on engine off.

As always, thanks for the time taken to consider my stranded in Craig Colorado ass issues

[cadillackid]

I thought the HCU motors just provided power assist... ie if you stand on the pedal with both feet you can still stop the bus.. that controller is a source of MANY issues on those and the similar IC BE model busses (they use a similar controller).. you can buy the motors separate if its actually the motors that are bad.. but from what ive heard it ends up being something other than the motors most times. . or if a motor goes bad and simply pulls a little more current than it should it blows the control board inside the device..



I have not personally worked on pone of these systems, just talked quite a bit to a friend who (moved on from) a district where he had 3 busses parked on "back row" because of these systems and the parts being hard to get.. there is software to connect to them.. he had it on his laptop.. he had an adapter and wabco tools or some such... at the time i was visiting, I was thinking of buying an IC BE and so while he was working on one I drove it to see if I wanted one.. anyway I think if you want to do more than throw parts at it (couple grand for that controller machine).. then id look into getting the wabco computer program and seeing if the controller gives you any fault indications.

[Samarath]

Thanks for your input. A little nightmarish to deal with so far from home. I am checking on prices for the HCU as a whole, and if what you are saying is correct, I guess my master cylinder may need rebuilt or replaced since I am completely unable to stop. I have been wanting the nexiq to communicate with the bus anyway, but I am not sure how I am gonna pull off the cost of the diagnosis hard/software as well as the part. Maybe I can find a place to park for a month or two so that I can work up the funds to do this all properly.

Anyway, thanks for your help.

[cadillackid]

Originally Posted by Samarath

Thanks for your input. A little nightmarish to deal with so far from home. I am checking on prices for the HCU as a whole, and if what you are saying is correct, I guess my master cylinder may need rebuilt or replaced since I am completely unable to stop. I have been wanting the nexiq to communicate with the bus anyway, but I am not sure how I am gonna pull off the cost of the diagnosis hard/software as well as the part. Maybe I can find a place to park for a month or two so that I can work up the funds to do this all properly.

Anyway, thanks for your help.

busses can be expensive to maintain.. it sucks sometimes.. maybe sign up for one of the Citi or chase cards that has a 12-15 month 0% introductory rate... gives you a year to pay the money back without any interest.....

[Samarath]

Ordered the Nexiq today. Looking forward to getting our bus and dogs out of the sun...lol

[Samarath]

Update,

We got the Nexiq hardware and the Wabco software and have been diagnosing things for a day now. The pump motors in the HCU will not engage, and connecting to the ECU is a little intermittent, but I was able to find 15 stored codes. I am working closely with Wabco on the diagnosis itself, and they're pretty helpful.

I just thought I would share an update. I guess if anyone has wabco hpb issues, maybe we can meet up and plug in my Nexiq w/wabco software to assist as we're able. Thanks for everyone's help.

[Oldyeller]

Originally Posted by Samarath

Update,

We got the Nexiq hardware and the Wabco software and have been diagnosing things for a day now. The pump motors in the HCU will not engage, and connecting to the ECU is a little intermittent, but I was able to find 15 stored codes. I am working closely with Wabco on the diagnosis itself, and they're pretty helpful.

I just thought I would share an update. I guess if anyone has wabco hpb issues, maybe we can meet up and plug in my Nexiq w/wabco software to assist as we're able. Thanks for everyone's help.

Thanks for updating. It's nice to hear how these things work out. Please keep us up to date on what happens. Your thread caught my eye because I also have hydraulic brakes but mine are Bosch HydroMax.

[Samarath]

With the Nexiq, Wabco tech support, and software, I was able to determine that the HCU was bad, replace the part, and get down the road. I will probably bleed the system again, but the dash is clear of lights, my bus stops, and I even have a parking brake!

[Oldyeller]

Originally Posted by Samarath

With the Nexiq, Wabco tech support, and software, I was able to determine that the HCU was bad, replace the part, and get down the road. I will probably bleed the system again, but the dash is clear of lights, my bus stops, and I even have a parking brake!

Excellent news. I'm glad it turned out well.

[Jolly Roger bus 223]

ok old yeller? are you just trying to give others support while you suffer?
we are with you sir.
hate a damn computer but it is our life now.
wish you the best sir.