Hi All, new to this forum I have a issue with a 1979 Clark 35C wheel loader, when the machine is running the brakes will not release and the brake pedal will not move down it has a lot of pressure on it, if you raise the front tires off the ground the tires will not move if turn off the machine the tires will move. I have taken the brake master valve off and taken it apart replaced the o rings and put it back together and put it back on and I still have the same problem. The machine runs good otherwise. Does any one have any ideas on this problem I would greatly appreciate your input. Thanks. Chuck
How long have you had the loader? Did it just start this or something else?
We got it about a month ago and it has had the problem all along, we bought it knowing that the brakes were dragging. You can run the machine just fine but as soon as you let off the gas it stops.
Also if you step down really hard on the brake/clutch pedal it will disengage the transmission let go of the pedal and the machine goes.
No expert here, Have been unable to find the 35C breakdown, did find a model 55A and B and the system appears to be just regular hydraulic brakes. The 55 doesn't show a power assist but if the brakes are engaging and this is the drive line causing the issue. Does it use a brake booster and if so does it apply pressure to the system when the engine is started? I don't see the inner link between the brake pedal and the parking brake like on the older dozers and track loaders. If yours does not have the link between the two this would not be causing the issue. Are the brakes adjusted to spec?
The unit has disk brakes and there is no adjustment to them. The brake valve has 4 lines running to it the bottom line looks like it is a return line the 3 top lines appear to be a feed line, a trans disconnect line, and a brake line. When I had the valve apart the piston was not fixed to the rod it could float about a quarter of an inch and the top three lines ports were all open to each other on the inside. Also the pedal goes up and down with the engine off.
Probably uses the hydraulic pressure from the transmission to supply assist boost. With disk brakes I don't see it being with the brake system, I'm going more toward the hydraulic assist side. Something is applying to much pressure and applying the brakes. Will keep looking and hope someone else with more experience will come in.
Ok thanks
I have a 45C and my brake pedal doesn't move much at all either but has really good brakes, did the brake valve look good on the inside? maybe pressure leaking past the spool?
Yes I had the valve apart and replaced all the seals everything looks good but it did not change anything, pedal is still hard and the brakes are applied
I think its normal to have a hard pedal, my 45C while running the pedal is hard you can push hard as you want it barely moves and you will stop now! does you machine have just front brakes? my parts book shows 4 wheel brakes were a option, mine has 4 wheel brakes, have you tried disconnecting the rod from the brake pedal to the valve? maybe that rod need adjustment and while running its applying the brakes? is your machine Detroit powered or Perkins? I have the 4-53 Detroit if you drove my loader it feels like the brakes are dragging (there not) the transmission has a sluggish feel to it
My machine has 4 wheel disk brakes and I have the Perkins motor. When you raise the front wheels off the ground while running the brakes are applied shut off the engine and they rotate freely start up the engine and the front wheels are stopped. The thing that gets me is when the machine is off you have about 1.5" of travel and when it running it is almost 0 you have to weigh 600 lbs. to move the pedal down. I haven't had a chance to disconnect the linkage rod to the valve and see if it needs adjusting. Like I said earlier this valve has the three line ports on top and they all are open to each other (strange system). AllDodge said earlier that there must be to much pressure going to the valve that is something that I need to also check out. I was hoping to hear from someone on here that used to work on these Clarks 35,45, and 55's especially on the hyd. systems, but I still appreciate all the info I can get from all who respond. Thanks.
I checked my 45C yesterday when its not running I can push the brake pedal down a good inch and a half just like yours and while running its very hard, really dont move at all but there is a little play I can feel in the linkage before its hard pedal
Well I finally figured it out and it had to do with the threaded rod linkage from the pedal to the valve. The owners before us must have had a problem for awhile because the replaced all the brake pads all we did was readjust the linkage longer and it took care of the problem. The valve rod must be all the way down to the bottom of the valve for it to work correctly. Thanks for all who responded.