Posted 5/14/2019 18:50 (#7497373) Subject: 4720 JD Sprayer: Air lock on boom valve block?
I need ideas on my 4720 sprayer boom valve block. Here’s what I think I know, but I wasn’t there.
1. The LH boom unfold hydraulic line blew. Operator kept trying to unfold, and basically emptied the hydraulic reservoir. (I’m trying to be economical with my words here...:-)...)
2. So, I replaced the line and filled the reservoir. The sprayer moves and steers, and the product pump runs. But the pump and steering both “talked” a little as the air worked through the system. So I’m fairly sure everything sucked air.
3. None of the boom functions work. No fold or unfold, no main up/down, no tilt.
4. The boom block (the valve block high on the boom arms, with 8-10 solenoid valves on it) is getting flow. The feed lines jump when any of the joystick buttons are pushed. But none of the pressure makes it through the valve block.
5. So...is there a bleed plug somewhere on the boom block? There are a couple of likely-looking plugs on the RH side of the block, but I didn’t want to just pull plugs without knowing what I’m doing.
6. Of course, this developed just after quitting time at our local (and good, IMHO) Deere dealer. If I don’t glean any ideas from the NAT brain trust tonight, I’ll call them in the morning.