CAT 518 Brakes

[Bobus2003]

I'm tryin to fix the Brakes on a '91 CAT 518 Grapple Skidder. It has the Air/Hydraulic system. Its building plenty of air pressure, I just cant get any Fluid to the calipers. I pulled the Air pancake/Fluid Reservoir from under the Left Foot floor panel, and Butler CAT rebuilt it, Re installed, refilled with fluid, and the reservoir next too the seat, but i still cant get any fluid to the calipers.. after 30 minutes was able to get a few teaspoons of fluid, and a little resistance to the pedal, but nothing that will stop or slow the machine.. any help or suggestions? Thanks

[captain_crunch]

Just a guess but what happens if you take line loose at Calipur to see if blockage is in line or Slave cylinder 518's generally have fantastic brakes and will stay where parked

[Mark K]

Could you use a vacuum puller like we use on hydraulic clutches to pull fluid to the caliper. Used one on my F350 Ford to bleed the slave cylinder on the clutch. Tried to bleed it the normal way and couldn't get it to pump up.

[Bobus2003]

Just a guess but what happens if you take line loose at Calipur to see if blockage is in line or Slave cylinder 518's generally have fantastic brakes and will stay where parked

This rig is like most the 518's i've delt with.. No Brakes! I will pull the lines off the calipers and see what results

Could you use a vacuum puller like we use on hydraulic clutches to pull fluid to the caliper. Used one on my F350 Ford to bleed the slave cylinder on the clutch. Tried to bleed it the normal way and couldn't get it to pump up.

This was something I wondered was even possible on the skidder.. guess its worth a try

[snowstorm]

never worked on a 518 but i do have a 920loader may use the same set up? did someting smash a brake line? the air is used to boust the brakes. got air is it moving the piston on the master cyl?could be leaking by inside. its about the same setup as on a car. just boust it with air

[log cutter]

 
Is it your front brakes you are having problem with or the one one the drive line that goes to the back axle? On my 84 cat 518 sn 95u. the Reservoir under left foot is for the drive line brake. The master cylinder for the front brakes is under the Right floor board. it feeds from the reservoir by your seat.   The  front brakes master cylinder has a bleeder screw on top open it up until the fluid runs out  then close. Then open the top bleeder screws on your calipers and pump your brake pedal, should work. For bleeding the drive line brake caliper, I fill the reservoir then open the front bleeder screw on the caliper, then I take out the little breather out of the master cylinder cap and then take my air hose and give it a little pressure and brake fluid should come out. Hope this helps. another things to look for does your brake line have a hole in it?

[mills]

I had the opposite problem with my 86' 518. The brakes were not releasing completely. It wasn't noticeable in the woods, but they would get hot when moving between jobs. I tried to put the repairs off until winter, but come close to burning it up going to the last job of the year. Got it home by cracking open the bleeder valve to relieve pressure at the caliper.

Started by changing out the diapram, but with no luck. Then changed out the master cylinder, but the rebuild wasn't correct, and couldn't get it to bleed off. Took it back to the dealer and tried a different one, and finally the brakes started working like they are supposed to.

[Bobus2003]

Ok, so I tried to get the brakes to work again today as were gonna need to use this machine again.. I got fluid to the calipers.. Pumped them up.. and bled them out a few times.. If I pump the pedal 8-10 times and hold the pedal down The brakes will hold the machine in 1st Forward or reverse with the accelerator floored, If i let off and start moving and press the pedal it takes about 2 seconds for the brakes to actually stop the machine. BUT if i let the machine sit for 5-10 minutes i have no brakes again and pumping the pedal doesn't always cure it.. What could the problem be?

[logloper]

After you let it set and they dont work, check your brake fluid reservoir and see if the level has gone down. If so, you have a leak and the line is slowly bleeding off. The line is hard to get to with the belly pan on. We had brake trouble for a while and learned it was easier to drop the pan in order to do the work. You might have a loose connection at the tee where the line shoots out each axle.

[bushmechanic]

Sounds to me like you still have air caught in the system.Keep in mind that air will compress and you will get a brake but let it sit and the air will un-compress and then no brake again.

[Bobus2003]

Its too the point where most the time its got brakes, but you will step on the pedal when backing up too the drag and they will hold, but if you do a "double tap" the brakes fail