93 international hydraulic break press light on

[Goblins]

So we bought this bus. Drove it 6 hours home. The brake press light was on. The guy we bought it from said it was something with a sensor. The brakes worked perfectly fine for the entire drive. There is no alarm going off. (Not sure if they disabled it) We want to further diagnose this issue and see if it really is just a faulty sensor.
Bus context: This is a 93 (initially built late December 1992) bluebird on an international 3700 chassis with a 7.3idi engine and hydraulic brakes.
We are going to check fluids and try to locate the sensors. It would be really great if we could find a manual on our bus. Is there any advice y'all might have for our situation?

[s2mikon]

First word of advise. Never drive a vehicle that has brake system warning lights on until it is fixed or determined to be safe by a knowledgeable person! I'm glad nothing bad happened. Heavy vehicles crashing into small cars can and do cause severe injuries and death. Remember we share the roads with other people and their safety is just as important as ours.

[ewo1]

Take a look over at this thread.

I uploaded the "Brakes" section from an International Amtran service manual. It is good for the 1999 busses but may also be real close to what you have.

[Goblins]

Originally Posted by ewo1

Take a look over at this thread.

I uploaded the "Brakes" section from an International Amtran service manual. It is good for the 1999 busses but may also be real close to what you have.

Wow, this is amazing and exactly something we needed. Thank you so much!

[magnakansas]

Chevrolets have “hydroboost” pretty much everybody else has “hydromax”.

These systems use power steering pump pressure to give “boost” to the brake pedal.

Sounds like, to me, the system thinks there is a problem.

Many possibilities. Could be as simple as a connector not plugged in. Could be as complicated as an intermittent power steering pressure problem.

The fist step is to identify which of the two systems you have.

Then read manuals about how the system is supposed to operate.

Read manuals for both systems, I think this will help increase your knowledge base.

I spent 15 to 20 hours looking up information reading materials, and videos.

Then I spent 10 hours or so rereading. After that I felt I knew enough to look into the “hydromax” system I had on my 1989 U-Haul.

I had a broken wire on a pressure switch. The system was operating correctly, but I did not know until I learned how the system worked.

Good luck.

[Goblins]

When we dug into it, our sensor was physically broken so we need to replace that to continue trouble shooting. We noticed there is not a fluid level sensor but I didn't see connections for one but it could have been tucked up somewhere. Is it common for this make not to have one?
The master cylinder when opened said "fill to bottom of ring" we think it means the bottom of the fill cap hole but if anyone thinks that's wrong please let us know. There is a molded plastic seam that might be a "ring" it's about 3/4 up the cylinder.

[Goblins]

Originally Posted by s2mikon

First word of advise. Never drive a vehicle that has brake system warning lights on until it is fixed or determined to be safe by a knowledgeable person! I'm glad nothing bad happened. Heavy vehicles crashing into small cars can and do cause severe injuries and death. Remember we share the roads with other people and their safety is just as important as ours.

This is good advice and I appreciate it. It was minimal risk in our case because no one was on the roads at the time. It was checked by a dot inspection before we drove it home. We did trust the seller too much though and I don't recommend anyone doing that. We're obviously not driving it anywhere else till we get it fixed.

[cadillackid]

driving with that sensor broken means the auxiliary motor probably ran the whole time, if it still works id be amazed.. its not meant to be continuous duty.. its supposed to be used for emergencies ie if the powered steering loses pressure then the aux motor runs.. you would normally run it long enough to stop.. but not driving for several hours... if the aux motor is still good than its a testament to how strong it is///

[Goblins]

Ugh, were troubleshooting replaced the sensor it was full of locktite. But cleaned it out and plugged the new one in and now we hear a motor that wasn't coming on before maybe it's too tight or not tight enough idk we're in a parking lot researching.

[Goblins]

Ok .. we jiggled the corroded connection and the punp went off and the brake press light went off thank y'all again for that link to that thread of manuals. We drove and everything is working and the light and the pump didn't come back on. We need to probably order a new cord/connection for that but it's at least comforting to realize we weren't driving with our pump on the whole way and that if it comes on it's probably that connection. Now onto the fuel sender lol.