My brakes recently started acting up. When I press the brakes either peddle they apply but release if I hold the brake on. Same goes for the air park brake, if i pull the knob it applies but realeas. Air pressure is around 100-120psi Not sure where to start on diagnosing the issue. Rear brakes only, front calipers need seals. Any idea what my issue could be? Clark Michigan 55B with v378 Cummins
Update Well I had a chance to use the 55B the last few days. Getting things ready for the deep freeze. Anyway I finally had a leak, it was leaking from the rear brake hose, from master cylinder to calipers. The outer layer must have been holding the fluid beforehand because nothing leaked a drop previously. About 8" hose. So I had a new one made and after installing the new hose I had more solid brakes but they still released after about 5 seconds. I let it sit for about 10-15 minutes with the air park brakes on and after I released the air park brake fluid came from in-between the master cylinder and air cylinder. I'm assuming my master cylinder isn't holding pressure causing my brakes to release after 5 seconds with the peddle held down? Looks like the part number for the master cylinder repair kit is 961122 but I can't find any repair kits available. Did Volvo supersede the kit number? Any help figuring out what seal/repair kit i need would be greatly appreciated. 433B-721-CAC is my machines serial number.