barke press lite

[colliervilledave]

On my shake down run to Talladega,about 5 hours away, about a hour into the drive i get a Brake press lite and buzzer . I still have good brakes, i stop check fluid levels in the master cyclinder,and power steering level,both ok i ve been told low ps fluid can cause this. cranked up warning stopped, drove two more hours warning poped back on....drove the rest with buzzer on ,,onthe drive home made about 4 hours and almost home then it poped on again any suggestions help.....

 

[the_experience03]

The brake pressure light is most likely caused by a failure in the hydroboost system or in the warning light circuit itself. Chances are it is only a problem with the sensor that is detecting power steering pressure to the brake booster. You should check things over though. Low fluid is a likely cause. Without enough fluid it will be impossible to generate enough pressure for the brakes, especially because the brake booster is likely higher than that power steering pump whereas the gearbox is lower. Gravity dictates that the gear box is going to maintain pressure long after the brake booster looses it.

So for diagnosis...

Does the electric backup motor come on when the light illuminates?
Does the steering feel get heavier at all?
Is the poewr steering fluid higher enough?
Do you have a leak somewhere causing a pressure differential valve to turn the light on because one of the circuits has low pressure?

 

[lapeer20m]

i had the same problem and was unable to find a solution. I was on a trip cross country and about to drive through the mountains. My breaks were definately working properly, fluid wasn't low. With the engine off my backup booster still worked properly. Everything checked out. I never did find a solution...except to remove the alarm "dinger" from under the dash. The downside is that this is the same alarm that sounds when your engine overheats, which happened to us later on in the trip when we lost an alternator belt.

this was a 1991 international with dt360

a school bus mechanic out there must have seen this problem before.....but i din't have any luck finding the answer. my local bus garage has air brakes on all of their buses, so they were only able to speculate that it was a bad sensor.

 

[colliervilledave]

Sounds like a good place to start looking, that sensor may be the problem.. now to find it.. I am not even gona go looking for 2 weeks need the break from the marathon get the bus ready party i had for the 3 week all niters trying to get its ready for my wife and me to take the Talladega trip....its was tuff but worth it it was nicer than the pull behind camper we use to take.....thanks for the info you guys have been very helpfull on all the questions a newbe like me has asked in the past...