Hi, Have just acquired a Krupp KMK2025 and I'm trying to fix a number of issues. The one that is currently causing me issues is the handbrake in the drivers cab venting when the brake is engaged. This drains the air supply (circuit 3) which results in no throttle and not enough air to engage the hydraulics. The current workaround is leaving the parking brake off and chocking the wheels which is obviously not ideal! Have stripped the parking brake valve (Wabco 35) and it looks to be operating fine. Anyone got any ideas what to look at first.
Where is the air leaking out from? The air system is really the same as any truck air system, just with wedge brakes instead of s-cams. Its not really anything exotic. The valve on the dash could be bad and allowing the air to escape right there in the dash, or you could have a different air valve hung up in the system. With air system issues, I like to get a separate air supply (electric air compressor) plumbed in, and then I can test the system without the crane engine running, so you can hear where air is leaking from.
The air is venting, continuously, out of the plastic vent at the bottom of the hand brake unit. There is no pipe attached and if I block up the hole with a screw head, I get the throttle back and I guess everything else on that circuit. There are two feeds to the unit, one slightly bigger than the other. I guess the big one is feed in and the smaller one is out.
So- when the handle is in the "park" position, this valve removes the air pressure that is holding the spring cans, and the springs activate on the wedges, and the springs hold the brakes in "park". When you go to "not Park"- park releases (want to drive)- it will supply air to the air chambers, pushing the spring brakes off the wedges, allowing the wheels to turn. So you've got two possibilities, either this valve is bad and when you go to park, its not shutting off the supply correctly and allowing supply air to go to the exhaust. Or you have something messed up downstream, and its backfeeding supply air from some other slave valve, to this valve's exhaust port. Pull off the air lines and see what line does what, and it should be pretty easy to find out if the problem is in this valve or if its coming from somewhere else.
Thanks, will have another look. Of course, it will be complicated by the hand brake lever in the crane cab
Yes, it could be backfeeding from the one in the upstairs cab, or it could have swivel issues, and leaking air there between supply and delivery in the swivel. That's why you're going to have to start pulling lines off and finding out what is supply and what is delivery so you can tell what's wrong.