Hydro-boost braking systems

[Bobalos]

I have a 99 ram with the cummins and a hydro-boost braking system. 2x4, auto, disc/drum. I've put all 259k miles on the truck.  

I have not been driving it very much, so I try to dive it on Fridays and the weekends, which is less and less.  

I moved it the other day and noticed the brakes werupsuper grabby and touchy. Little brake pressure and it felt like the fronts locked up. 

Yesterday on the way home, it locked up at least the drivers side front, maybe both, with very little brake pressure. It didn't twice.  

Then when I got aggressive with the brakes intentionally, it seemed fine.  

Anyone have any suggestions on where to start with this? Is this a hydro boost issue? The steering seems to be reacting normally. Is this a proportioning valve issue? Maybe one Caliper??? Nothing is super old. Hoses, calipers, Rotors drums, shoes, power steering pump, wheel cyls, all been replaced not that long ago.  

 

[1HasBeen]

Was the caliper hardware replaced, too? Maybe corrosion on pins/sliders?

 

[Sausage450r]

Check the “abs module”.  Had a similar thing with our excursion. Replaced the master cylinder. Nothing. Took it to ford they said its “normal”. My regular mechanic replaced the abs module and its all good. 
 

Excursion pedal would also slowly sink at stoplights. 

 

[Bobalos]

When the calipers were replaced all of the hardware was done. This thing goes through front brakes like mad (when empty, which it is most of the time, and will be for the rest of its life).  

This has rear abs only. I will remove the connector for rhe abs and see if it is normal or not. I've done that before and the truck drives perfectly with it unplugged.  

By abs module, do you mean the electronics or the valve assy or both?

Thanks for the ideas...  

 

[Chingon619]

I pulled my abs fuse on my truck long time ago. It will never lock those 35s up, ever lol. Otherwise, I got nothing for ya. Good luck! 

 

[Sausage450r]

When the calipers were replaced all of the hardware was done. This thing goes through front brakes like mad (when empty, which it is most of the time, and will be for the rest of its life).  

This has rear abs only. I will remove the connector for rhe abs and see if it is normal or not. I've done that before and the truck drives perfectly with it unplugged.  

By abs module, do you mean the electronics or the valve assy or both?

Thanks for the ideas...  

maybe bad proportioning valve?