I have a 1987 ford f700 having trouble with
The parking brake it has the hydro boost
Brake system when I press in the parking
Brake the brake pedal get hard and in possible
To press

Any thought ??

 

Your parking brake, is it a yellow "pull for brake/push to release" **** on the dash?

 

Yes that's right and it has two lock down chambers on the rear breaks

 

Can you see the words "Lucas Girling" anywhere on any parts?

 

Yes that's what it is foreshore

 

OK to get you going read this thread on the subject. Note there is a link to tools in post 3:

https://www.ford-trucks.com/forums/9...ke-system.html

More detail and links:

https://www.ford-trucks.com/forums/1...1995-f700.html

OK I gotta stop here: Are you a good wrench man with brake experience? In my opinion, a medium truck with this kind of braking system is not something to tinker with and try to learn in the field. If you are not comfortable with this, find a shop, or at least run down a factory manual to consult while working on it.

Downloads here, google will be your friend:

Ford F600 Lucas Girling Brake System > Priority Documents

 

This one too:

https://www.ford-trucks.com/forums/1...omax-info.html