Question RV Brakes

[lrhumphreys]

Our brakes completely failed on our Motorhome. I mean all the way to the floor and stayed there. No fluid loss or leaks. Replaced master cylinder and got home safely. My thinking is the heat in the doghouse heating the master cylinder, causing failure of the seals in the master cylinder. Has anyone experienced this? 2002 R Vision.

 

[jbh]

Probably not heating of the master cylinder but rather boiling the brake fluid. When did you last completely change the brake fluid? How did you determine that the problem was the master cylinder?

 

[lrhumphreys]

Just last season all new brakes and fluid was flushed. After losing brakes to the floor I checked for leaks and fluid loss and had none. Just thought that the master cylinder was the corporate so change it and was fine for a ride home. Broke open the old master cylinder and really found nothing deteriorating from the seals. Right now it’s still a mystery to me. Only part that has not been changed is the hydro boost.

 

["EZ"]

You don't have your profile filled out so we don't have any idea how old your RV is or what type it is, so it's hard to help with good information. How old is this thing?

If you are not losing brake fluid anywhere then I'd bet it is the hydro boost. I have a 1966 Cadillac Coupe DeVille. The power brake booster failed and it's like driving a car with no brakes! No fluid leaks and all brakes look good. But the diaphram apparently has a hole in it or has dry rotted over time and has cracks in it that leak all the vacuum out. The pedal is very soft. Sound familiar? Maybe this is your problem?

 

[jbh]

It's really surprising that you'd have a complete failure of the master cylinder. Maybe internally plugged somehow. If the mc leaks it'll come out the weep hole between the mc and the hydroboost. If you lost the hydroboost you'd have very hard brakes.

 

[Alan_Hepburn]

Usually the master cylinder is mounted on the firewall, not somewhere under the doghouse...

 

[WinMin4]

This happen to me on the PU truck it was a leak rusted brake line. I bled the brakes pain in the ass especially if the bleeder valve are rusted on.