Hey guys,


I recently acquired an 85 F250 with the 7.5l 460 gas engine, and the brakes have been a little squishy. After checking and cleaning all the brakes, I went to bleed the brake lines and discovered a small brake fluid leak from a part that I can’t identify. I couldn’t find a comprehensive diagram of the brake lines online, but the part in question is connected to the rear axle vent tube. I had trouble bleeding the rear brakes (even after inspecting and cleaning the bleeder valves - which looked great), but the front brakes bled beautifully. I was wondering if this leaking component could be the cause before I investigate the possibility of a blockage or leak elsewhere. If this is the source of the problem, I would like to know what it’s called so I can fix or replace it.

Thanks in advance for your response!

20201125_124743 by JimmyJames posted Nov 26, 2020 at 12:01 PM

20201125_125927 by JimmyJames posted Nov 26, 2020 at 12:01 PM

 

it is a valve that limits rear brake pressure according to weight. the more weight on the rear of the truck, the more rear brake pressure you will get.
the idea was that with less rear braking when empty, you will have less chance of rear brake lockup.
sorta like the rabs valve that ford went to in 87

 

Wow, thanks for the quick response! Why would it be leaking without a load on it, and do you think that could the source of my brake issues? If so, do you happen to know the name of the part?
Thanks again

 

it could be anything leaking. bad seal, old line are two things off the top of my head.
as for hat it is called, my best guess is obsolete.
they have not been used in over 34 years, and i have not seen one that worked in over 30 years.
even when they were new they did not work very well, just like the first generation RABS valves.

 

Ha, I'm not surprised they're obsolete. Are you aware of any way to safely bypass and abandon it? I doubt I'll be able to find a new one, but I may get lucky at the scrap yard...
In the meantime I'll take a look at the mastery cylinder seal and also see if one of the brake lines are clogged. Suggest anything else? Thanks again