Brake Pressure light..

[colliervilledave]

Hey gang need some help , my 94 international 7.3 liter ford ...The brake pressure lite and buzzer goes off about ten minutes into every trip. Checked all fluids brake and stering, the bus stops fine,where do i go to next thanks

[crazycal]

The 7.3 is an International engine. Ford buys them from Intl. If you have a guage that tells you that you're losing brake pressure, I would think you would have air brakes. If you have hydraullic brakes and your light comes on, I would think your fluid would be low.

[the_experience03]

My vote is sensor, but it's possible I suppose that once the power steering pump heats up it goes out of tolerance and rather than pressurizing the fluid it just shears it. Your brakes would still work fine thanks to the electric backup motor. Do they still function correctly with the electric backup motor disconnected? A power steering test set could prove to be extremely helpful. A little over $100 gets a gauge set that will tell you your deadhead pressure off the pump. Maybe a local VoTech can look at it for you even. But I still vote sensor...

[colliervilledave]

Thanks I will start with those ideas ,they are hydraulic . Would any one know where to look for that sensor off the top of your head.. thanks

[lapeer20m]

on the side of the master cylinder. you should see a connector there. that is the sensor(s) Check first to see if you can clean the contacts on the sensor/connector, that very well may fix the problem.

i'm not sure how to test the sensor with a multimeter.... I don't know if it should be either open or closed when there is no pressure on it. I suppose you could use the multimeter to see if it's either open/closed with the engine off, then switches to the opposite when the engine is started.

a good test for your brakes is to unplug your electric backup (it's the motor you hear running if the key is on and the engine is not running) If you unplug this and the bus still stops then it helps rule out a faulty ps pump. Another ps pump test it to turn the wheels from side to side while the bus is not moving. if the steering wheel turns easily and the pump doesn't whine, then it's quite likely the pump is ok.

To rule out the electric backup as faulty.....re-connect the electric backup motor, with the key off in a safe place see if the bus will stop when the engine is not running. If the bus stops, then the backup unit is likely ok.

if both of these systems appear to be functioning properly, the most likely culprit is the sensor.

[colliervilledave]

Well it looks like this weekend is work onthe brakes time thanks for the help, one more question were could a fellow get a maint manuel to do scheduled p@m on the international bus thanks

[GoneCamping]

If you got hydraulic brakes then you probably have a Hydra-Max of some sorts in that thing, and that could be defective too. It could something as simple as the pressure switch that could be bad.

I used to drive an F800 Rollback Wrecker with a Cummins motor in it, and the brake warning light would come on after a while and stay on until I shut the thing down and left it over night. It turned out to be a sticky relay, I found I could pop the hood and "Thump" the relay with my finger or thumb and everything would go back to normal...

Lots of places to go with this one....