I have a 1988 JCB 1400B, the brakes are hung up and I have no idea what to do. The machine will move, but at low speed you can hear the brakes moaning. At higher speed it does not want to turn as the front wheels are barely getting traction, then when you let off gas or throw to neutral it stops pretty fast. A little background: a while ago, the brake pedals went pretty much dead until they hit bottom, then the brakes would engage. So i tried my hardest not to use them (this machine was purchased to do an addition and septic system on my house). While digging the septic drain field I noticed when i went to move the machine a little to use backhoe, the brakes would whine(low pitch hum). Now I need to fill in trenches and am clueless as to where to start looking for the issue. I am mechanically inclined and follow directions well so any tips/wisdom would be greatly appreciated. Also, the reservoirs in front of counsel are full. In all honesty, if i could disconnect the brakes to finish project, I would be fine with that. I baby it, go slow and in wide open area, can always stop with a drop of the bucket.
Not sure if you know this but these machines don't use brake fluid, they use a light hyd oil, I've had good luck with using ATF. You could open the bleeder on each brake housing (right behind rear axle) see if pressure is building? I did a complete brake job on one of these a few years back, parts are readily available, the master cylinders are a pain to get to but otherwise a straight forward job. Are you sure it's the wheel brakes dragging and not the driveline park brake? What condition is your rear axle fluid like? (Needs TDH fluid)
As GregsHD said release the the bleed nipples on the top of the rear axle and see if you have pressure built up possible master cylinder fault ,check that you have free play on the master cylinders as this may be causing the brakes not to release.The fluid should be a light hyd oil and not brake fluid as this will destroy seals in the axle and m/clinders. What condition is the oil in the axle ans does this machine do a lot of road work or on the brakes all the time,if the rear axle oil is burnt and very black may have a problem with the friction plates buckled but this will usually show sighs prior to locking up of a spongy break pedal.
The oil for the brake reservoir is mineral based oil like this.
Thanks for the replies. I am aware of the fluid. I have not had to add any. I will check the bleeders. Are you saying it could be like a car and have some sort of air lock? What exactly do I want to see when I crack the bleeders and what steps should I take depending on what they do/show? Not sure about the driveline parking brake, have never used it (lever not in good shape so I never touched it). This project is taking forever, doing it myself, but last summer when digging crawlspace, things worked fine, then fairly quickly the pedal went soft and brakes would only engage when fully pressed, so I tried not to use them. Then when digging with backhoe, went to move machine back 8 feet or so, and put in gear and noticed It would not move unless I gavee er some throttle and when she moves she makes the moan like brakes are hung ( kind of like in a truck when you just barely let off the brakes and give some throttle and it moans a little).
When you crack the bleeders with no pressure on the brake pedal, there should be no pressure at the bleeders. The fluid will probably seep out, but shouldn't squirt much. If you drain the fluid, then the brakes are basically disconnected, unless you have warping or something else going on. It's relatively easy to diagnose brakes on a backhoe, lift the wheels off the ground, put it in neutral and see what moves. Try it with the engine running and off. With the engine running one or both wheels will creep on a typical backhoe, no experience with a JCB but how different can they be?
If your brake pedal has sunk to the floor as to speak it could be one of the master cylinders stuck ,unlock the bridge lock between the pedals and and see if they feel the same. As delmer said lift up the rear end and let the machine try and turn the wheels in drive see if its both or just one side . When the friction/counter plates warp in the axle from heat or worn thin the internal brake piston will be pushed back into the axle housing as the friction plates look like a Bellevue washer as to speak and acts as a spring so when you push you break pedal down the following happens. On pushing pedal down the piston pushes out of the axle housing and compresses the friction plates as these are warped they act like a spring trying to push piston back again so the feel of t=no pedal as you have hit no resistance yet,but if you pump the pedal you will get a brake pedal and stopping power but soon as you let go of pedal it will push the piston all the way back in the axle housing again . If the brakes are hyd locked the master cylinder is not returning and allowing the oil to vent through the the piston into the reservoir and releasing the brakes so that means as soon as you undo the bleed nipple it will be under pressure so releasing the brake. If its master cylinder change both out bit of a pain and will need an extra pair of hands to assist. To bleed out the brakes unlock the lock so as independent brakes , Hold the left pedal half way down and bleed the right hand side with a tube on the nipple into a jar with the pipe under the fluid level so not to suck up air and bleed through. Repeat the other side by holding right pedal this time half way this is so it will bleed out the link pipe between the master cylinders.
Well, when I got home I checked the fluid, both reservoirs full, then I cracked the bleeders and just a slow steady flow from each. Fluid did not appear bad or smell burnt. So I started her up and put in gear and it was fine, no more hang up. I used it for awhile and never touched the pedals (did check to see how they felt before getting going and pedals have no pressure to them at all). I really need to get this addition and septic finished to refinance, funds are about gone. Hopefully I can limp her thru finishing filling in the drain field and move a little dirt , then get back to trying to figure out the problem with the hoe after completing the addition. Again, thanks for all the feedback.