[Cummins12V98]

First thing is your actuator making noise when applying the brakes? If it is do the following.

Looking at the water manifold now look to the left. It's a silver aluminum box about 3" wide and 8" tall with a black cap on the top. Remove cap look inside is there any brake fluid visible? Stick your finger down into the hole is there any on your finger?

If you can't feel the fluid and actuator has no fluid you have a huge air gap and the brakes will not work or very poorly. Cure is to bleed the brake lines. I "HIGHLY" advise doing the job right where you are! do not take your RV onto the road with NO brakes!!!