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High Road Travelers · 09-27-2021, 12:48 PM

I washed my radiator fins yesterday afternoon with a hose to clean bugs, etc. and now the motor for the Hydromax Brake Booster runs continuously, with the engine off and the ignition key off. I assume something got wet and shorted out or something of that nature. I did not notice it until I went out this morning to put the garbage out and I heard something running.
I called the service manager at a ford truck dealer and he told me where the electric plug is behind the master cylinder and I unplugged it, so it it not running now. (plug is very difficult to see and to get your hand in there to unplug - it is a white plastic plug).
I let it sit all morning to dry out (the radiator fins are still wet) and then plugged back up, and it still runs continuously, so I unplugged it again. With it unplugged, if I turn the ignition key to "on" I hear the motor just for a second or two, then it shuts off. This seems strange to me, but there must be another connection to the pump motor under the dash or somewhere.
My Question: Is there a relay or a "reset" somewhere for this Hydromax system that I can reset, or does anyone understand what is happening?
Thanks,

High Road Travelers · 09-30-2021, 01:37 PM

Resolution by the OP:
It took about four days, but I guess it eventually dried out. I plugged the motor back up today, and it seems to work fine. I do not hear anything running unless I push the brake pedal with the engine not running and the ignition on. This is the way it has always worked.
I have not test driven it yet, but I think something got wet that should not have gotten wet; and everything is OK now.
Offered just as info in case this happens to anyone else.
Thanks,

US1 · 09-30-2021, 10:02 PM

Good to hear. I dont have to have the ignition on for my pump to run

pneumatics · 08-04-2023, 12:06 PM

If the OP can comment, this just happened to me with 2019 F-53 Ford. The Hydro-Max booster motor turned on just sitting there overnight. AFTER I washed the radiator as you did. Did it return after drying out? Figure out what may have caused the relay to pull in and drive the motor continously?

High Road Travelers · 08-05-2023, 08:35 PM

Quote:

Originally Posted by pneumatics

If the OP can comment, this just happened to me with 2019 F-53 Ford. The Hydro-Max booster motor turned on just sitting there overnight. AFTER I washed the radiator as you did. Did it return after drying out? Figure out what may have caused the relay to pull in and drive the motor continously?

I unplugged it behind the master cylinder and let it sit for several days and plugged it back in and it worked properly. I have not had an issue with it since then. I have been very careful washing my radiator since then though.
Thanks,

pneumatics · 08-07-2023, 09:31 AM

Thanks for reply. A bit more information after talking to local Ford Truck service.
The motor for the Hydromax has the power + applied to the stud on top of the motor which is behind the relay that drives the motor, both immediately under the master cylinder. When this gets wet or oily it creates a 'short' from the stud to the ground and this fools the Bosch Monitor brake controller to turn on the output that drives the relay. From an electrical standpoint this sounds a bit sketchy but that is what the tech told me, they see it on trucks that use the same Hydromax set up. Cleaning the electrical connection and the area around it and letting it dry out solves the problem. The shop does the same as we did they unplug the relay to stop the motor and let the area dry out for a day and then it works fine. Not something they see on the RV striped chassis but on the trucks, yes.
So we are always learning new tidbits about these machines....