1990 Case 580K Backhoe. The brake fluid level was low and I added more oil to the mark. When I started driving in 4th gear, I noticed it slowing as if I were going uphill. I stopped and pressed the brake pedal. It no free play and no leak down. I pressed it several times and it then had some free pedal. All was well. I started driving again and the same thing happened, two more times without me pressing the brake pedal. Again, after stopping completely, I pressed the pedal two or three times and then had a small amount of free pedal. The brakes work when I press the pedal. The fluid level in the brake reservoir did not appear to change. This makes no sense to me. Does anyone else have an idea??
This is usually caused by there not being any/enough free travel at the push rods to the master cylinders or broken pedal return springs. As you drive down the road, the machine bounce causes the brake pedals to move up & down slightly, thus applying the brakes. ..... You are using mineral oil to top the master cylinders & not brake fluid?
alrman: My memory thinks it is normal hydraulic oil in the brake fluid reservoir, and that is what I used. I need to check the book to verify. The road was bumpy and the heavy rear end caused the machine to lope which required a slower speed. The pedal springs are good. Each time this occurred, I stopped, pressed hard on the pedals two or three times which gave some pre travel and also released the brakes so I could proceed. I had to stop three times in the three miles to my destination. When stopped, the brakes are working fine, hard pedal and no leakage. Only about 2" of pre travel. During the trip, the brakes never locked up. Just began dragging the speed down as if going up hill in 4th gear. I might add, this happened once before in 2nd gear while working in the field moving dirt, back and fourth.
I had sticking brakes and the root cause was a stuck slave cylinder on one side. It could just be that. Some people are able to do the replacement from underneath without removing the seat & floor, I wasn't but repaired a bunch of things along the way.