I have a 1996 F500 with a 6BT in it. Everything was fine but I haven't driven it for a few months. I fired it up Friday night and the electric brake motor light was on, as well as the Brake light. Usually these cut off pretty quickly, but Friday they stayed on. I could hear the motor running under the hood.
I see no problems with the brake fluid level, but the pedal is hard, even when the engine is running.
I have not dealt with this type of braking system, with an electric motor backup on the hydro-boost. Does anyone know what's going on, what to check, or where I can find more information on troubleshooting this?

Thanks,
Chris

 

Does the power steering work? Check the fluid level and condition. There is most likely a power steering filter in the p/s reservoir make sure it is not plugged up. FYI the power steering pump also operates the power brakes.

 

Yes, PS is fully functional and the fluid level in the remote reservoir is full. I figured that if the PS was working I wouldn't need to worry about brakes because it looks like a normal hydro boost, just with an electric motor attached to the bottom. That's another odd thing. I'm guessing that the electric is a backup, if the engine stalls, but the brake pedal is hard now even with the engine running.

Thanks,
Chris

 

Yes sir the electric motor is a back up and should come on anytime you touch the brakes with the engine off. Is the electric motor running with the engine on?

I would pull the return line and run it into a bucket to see if you are getting adequate flow, also flush the system out. If you have good flow then suspect a faulty hydra boost. I would also disconnect the brake pedal from the rod and to make sure it is not seizing up from sitting.

 

Sorry, I missed that you had replied again to this thread. I looked at it some more and now I feel stupid. It turns out this system has two different circuits, one for the PS, driven off of the timing case, and one for the brakes, driven by a belt-driven PS pump. Two great big reservoirs, one mounted beside the radiator and one over the engine. I checked the one over the engine and added PS fluid and now the brakes act right again.
I plead confusion. Even with two circuits this sucker has a maze of hoses and fitting blocks so I can't really tell what's going on under the hood.

Thanks for the help,
Chris

 

You need to find the leak. If it was working correctly when you park it. Just my two cents, Mike.

 

Yes, the leak will be hunted down if it happens again. I have had the truck for 3 years now, and this is the first time I had it get low. I do not know what the fluid level was when I bought it because in my confusion I did not think to check that reservoir. I only checked the one that is suspended over the engine.
I will be keeping an eye on it though, in the every 6 months I drive it.

Thanks,
Chris