JCB 3CIII Powertrain (Build /5) - Brakes

steve ball · Post #1 by **steve ball** » Fri Mar 19, 2010 11:10 pm

Can someone please give me some advice on a problem that I have with the brakes on my 3CIII?

After coming to a halt, the brakes lock on and can only be freed by nudging the direction control lever into reverse and creeping back a foot or so until a loud "clunk" can be heard. This makes manoeuvering very difficult, particularly when trying to use the pallet forks.

Any suggestions as to what the problem might be would be greatly appreciated.

essexpete · Post #2 by **essexpete** » Sat Mar 20, 2010 12:09 am

Never had any trouble with our old Powertrain brakes other than squawk. Have you got oil immersed brakes? I am not sure if the early Powertrain had wet or dry brakes. I think you need to work out if it is a mechanical problem or a hydraulic problem. We have an old Sanderson with a dry hand brake disc that will jam on if applied hard when the machine is rolling forward. That needs a shift back to release it. I think it is due to a cam/ramp jamming. On the other hand there could be a fault in the hydraulic system. I have heard of problems with JCB handlers from the early 80s where the brakes would jam on when everything was hot and releasing a brake pipe would let off the brakes.
Hope someone can be of more help here.

steve ball · Post #3 by **steve ball** » Mon Mar 29, 2010 2:06 pm

Pete, thanks for the reponse. The brakes on my machine are dry ones, I think that the very late 3CIII's had wet brakes. When the brakes bind, it seems to be worse on one side than the other which makes me think that it is a mechanical problem.

I've tried slackening the brakes off and then readjusting but the problem remains. I also noticed that when the rear wheels are off the ground and are run up to speed in top gear, slight pressure on the brake pedal results in them picking up more speed. This makes me think that something is dragging and not freeing properly.

v64paul · Post #4 by **v64paul** » Mon Mar 29, 2010 5:03 pm

The actuators (between the brake discs) were always a problem. they expand when the pushrod pulls on them, this has the effect of making them rotate in opposite directions to each other. ball bearings between the plates sit in grooves that are machined into the plates. these act like a ramp forcing the plates away from each other.

essexpete · Post #5 by **essexpete** » Mon Mar 29, 2010 11:48 pm

So are the dry brakes of this era Leyland tractor brakes? If they are you could ask on the Brit farming Forum for some additional info.
Is there any way of lubricating the mechanism without contaminating the brakes?

steve ball · Post #6 by **steve ball** » Wed Apr 07, 2010 1:24 pm

Paul, Pete - thanks for the comments. I've had a look in the service manual and can see the disc / ball bearing arrangement that you mention. There's also several small springs in the assembly.

I wonder if one of these springs isn't freeing properly and causing the brakes to bind until you free them by changing direction?

When the ground dries up I'll start taking the brake assembly apart and see what's lurking within!

Thanks for the ongoing assistance.

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