i have a 2019 ih ce bus with the psi gas motor in it with hydro brakes this is the second time i am running across this issue i had a simpiliar issue with the sister bus when i first start it up th brake pressure light comes on and the alarms are going off then i shut off and restart and its fine well i did brakes on it yesturday now its on and wont go off i had the sister bus do the same thing after i did brakes i swapped out the switch on master didnt fix it swapped the presssure switch on hydro booste still no fix after some testing i deside to swap out the master and then it was all good and no problems since but i am thinking it cant be a master again any ideas
Post VIN so I can see specific system. But a couple ideas from what I know from years gone by. Based on this system using PS pump for boost. The flow switch/system can be very touchy on these. System wants to see flow immediately. If there is any lag in flow from PS pump it's going to trip the alarm. You could try getting the frt wheels off the ground so there is zero chance of a load on the PS pump at start. Most of these systems also have a switch on the M/C that goes to ground if their is any unequal output pressure out of the MC. That could be checked by unplugging the switch. All of the above based on what i think you might have. VIN would let me know for sure. One other general thing which I didn't know for a long time and should have. IF your pushing the caliper pistons back open the bleeder screws. If not you can backflow fluid into the ABS module which can cause problems. Have yet to see that cuase a problem in buses/trucks but apparently is becoming an issue on the car side as the systems are getting more sensitive. FWIW manuals as far back as the 1999 systems advise to do this.
lb231133 i hear u on opening the bleeders gonna start doing that just did front brakes on one today and now its doing the same thung as this one but i put a master on the first one and the issue went away still tryin to diagnois this one and see what happened
Sorry about taking so long. Been hectic. Are you still having a problem? Tried to look at SI on your system but Navistars site is acting up. If your master cylinder booster setup looks like the one in this link try unscrewing the switch that is between the the two brake lines. The brake line ports have a red and black plug. The switch is the yellow thing just to the right of the red plug. On the master cylinder. Plug it back into the harness and let it hang there. Start up and see what happens.
i swapped that switch out still had problem i ended up changing the master and the flow switch on the booster and now its ok but problem is i dont no which it was
I think your problem is in the master cyl. Specifically the differential pressure switch. If you want to email me contact info. rex@alliancemotorsinc.com a quick phone call might straighten this out. It looks like they went back to a system, the HydroMaxx, from about 20 years ago. I dealt with those buzzers lights and motors all the time back then!!
yes i believe it is the master i did another one a sister bus did front brakes and after was done same thing pressure lights and buzzers came on i am thinkin from pushing calipers in its doing something to master so gotta start opening bleeds when i do brakes on these buses
call your dealership (or check OnCommand,) and see if there is a recall on these. I seem to remember something about about a recall on the brakes on the 2019's, but can't find any paperwork on it.
19 ic hydro brake issue
Posted - 03/08/2023 : 04:38:34 AM
