Encountering occasional loss of braking when loader brakes have been applied for a period of time. This is a sudden loss of braking with the loader starting to move unexpectedly. The air pressure gauge shows adequate pressure yet the brakes do not respond if the pedal is pumped once. If you have any ideas, they would be appreciated. Both master cylinders have the correct level of brake fluid and the brakes work in a normal manner under regular operation. This failure only seems to occur when the loader is being held in a stationary position for a period of time ( say 3 minutes or longer).
That is a older machine, does it have a single brake pedal in the cab or two ?. I would first drain the air tanks and see how much water and oil is in the system, do a brake adjustment on all four wheels, bleed out the system. The machine has drum brakes and two wheel cylinders per wheel so it is important that the adjustment be up to spec and the flex lines in good shape so it's not swelling with pressure when the master cylinder is stroked. That being said you will more than likely have to rebuild or replace the air chambers and the master cylinders, kind of thinking the seals are shot in the m/c letting the fluid by passing back to the m/c under pressure and keeping it full. You have the air pressure on the chambers but if the seals are bad in the m/c it will hold for a short time but the longer it holds it's leaking back threw the plunger seals into the m/c.
Thanks for the reply. This machine has a single brake pedal setup. The one thing that I was wondering is why this would fail with separate master cylinders on front and rear, but perhaps one is failing first and when the second one does, then the brakes are lost. By the way this machine is located in Florida, so freezing temps are not and issue. We will check out the systems as suggested. We have an original manual for this machine as a guide.
you may have only one ,front or rear brake in adjustment and master cyl by passing. If I remember right brake chambers have indicator rods in them for checking master cyl if has them should have 11/4 stroke with brakes adjusted first and not drift off when looking at indicator ps don,t get run over under there.
Thanks for the information. The loader does have two master cylinders and the rear indicator does have too much travel. I have repaired the front master with a new kit and honing of the cylinder. This has improved the performance, however further work will be required to address the rear brake issue. The replies on this forum has been helpful.