Re: Re: Re: 1988 Lucas brake

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Posted by mike on October 26, 2007 at 06:02:18 from (76.118.8.75):

In Reply to: Re: Re: 1988 Lucas brake posted by Nick Rotolo on May 05, 2007 at 15:53:42:

I have a 1985 F600 with the Lucas brake setup and no one seems to know how to fix it so I am working on it myself. So far I have found a few things out. The motor mounted below the master cylinder is supposed to run only when the emergency brake is off, the engine is not turning, the key is on, and you step on the brake pedal. There is a relay that activates the motor, mounted on the side of the master cylinder just above the motor. There is a pressure switch on the other side that senses when the power steering pump that runs the brakes has no pressure, because the engine is not turning the pump. When there is no pump pressure it closes the switch. Then there is a switch on the brake pedal that tells when the pedal is pushed. This closes when the pedal is pushed. Then there is a relay above the pump motor that clicks on. The key has to be on to energize the system and enable the relay to close. The motor has a fusable link connected at the solenoid on the right front fender that supplies the motor relay high amperage contact. If the link is bad or disconnected, the electric assist motor can't run. Check the fan belt that runs the pump, because when you step hard it puts a lot of pressure on that pump, and it could stop the pump if you press hard enough (causing the belt to slip). I wish I had a service manual for this braking system. My assist motor won't run so I can't get an inspection sticker yet. I am thinking the main relay is bad and am going to test it today. I can hear it click when it is supposed to, but no motor goes on. More later.

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