Trouble shooting the ultimate spongy brake pedal

[Bluebird_Rory]

Hey all,

just purchased a 2000 bluebird bus, TC front engine. After replacing a bad alternator my next job is to fix the hydraulic braking system. The symptoms are: Almost no pressure felt in the pedal until the final 10% of pedal travel and brake light and buzzer both sound constantly from moment brake pedal is first touched, until engine is shut down.

I tried topping up reservoir to see if the warning would stop, but no luck. Previous owner said he thought it was a leak, but my feeling is it could be a failed pump? my research has made me think theres a hydraulic engine driven pump, as well as an electric back up.

Whats the best way to isolate and diagnose which is the problem?

Thanks in advance for any help!

 

[magnakansas]

Sounds like bendix hydro-max

That is the system with an electric motor used as a back up and that damn buzzer. There is out there, or was out there, on the World Wide Web, a operations/user/maintenance/troubleshooting manual a pdf file put out by bendix. I have a hydro max system on my 1989 international uhaul.


Hydro boost is the delco system.


William

 

[PorchDog]

http://1999southwind.com/DOWNLOAD/Bosch HydroMax Booster Manual.pdf


Here is some good info.

 

[Bluebird_Rory]

Thanks so much, a lot more useful stuff inn there than anything else i could find.

Much appreciated!