Hope you're doing well.
I'm reaching out because my team and I are having a significant, persistent issue with an H550HD forklift (equipped with a fork, GPI pipe stabilizer, and a PVG16 directional control valve), and we desperately need your expertise.
History of the Problem
The problem started 2-3 years ago when the hydraulic oil became contaminated. The tank was cleaned and the oil replaced. It recurred recently, which is when I got involved.
Repairs Completed So Far
Since then, after cleaning out the tank and changing all the hydraulic filters, we've replaced the hydraulic oil, carriage harness, all control valve seals, some actuators and PVEs for both the main and directional control valves, and re-kitted the main and tilt cylinders due to bad seals. The owners also replaced the hydraulic pump.
Current Situation & Symptoms
Despite these extensive repairs (re-kitted cylinders are fine, control valves serviced with new O-rings), we're still stuck. During testing:
The main lift and tilt arms are getting pressure.
However, there's no pressure or oil flow to the carriage (auxiliary) lines.
All PVEs on the main control valve show a green LED.
I haven't connected the carriage to the mast yet, as I wanted to confirm pressure to all channels first, though I did plug in the harness to avoid error codes.
Initially, the main lift and tilt arms moved quickly, but the carriage lines remained dead.
Then, the main lift and tilt arms began moving sluggishly, as if under strain, despite the auto-accelerate feature.
Eventually, all movement stopped.
My strong suspicion is the control valve, but given its cost, I'm hoping to get your insights before replacing it. Any advice or troubleshooting steps you could offer would be greatly appreciated.
Thanks,
Charles
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Now, the current situation i am facing on the forklift is the leakage of hydraulic oil from the differential housing breather.
My team's testing of the H550HD (25-ton) forklift has revealed a significant hydraulic oil transfer problem. The hydraulic tank gauge shows no oil within five minutes of filling, and the internal tank level drops drastically. Concurrently, the differential housing's oil level becomes excessively high, overflowing through the breather.
We suspect faulty brake seals or spindle-to-hub seals. Could any GURU in the house suggest other potential causes for this hydraulic oil transfer from the tank to the differential?
Additionally, we've noted unusual, intensifying noises from the front wheel when the brake is applied during operation.
Your expert advice would be greatly appreciated. We look forward to your prompt response.
Much thanks
Dove
Thanks for the input, @JKPAINTER. So, I got them flowing again by changing the pilot and check valve and servicing the priority valve. It was okay, but due to the sludge in the system from the fluid contamination and water ingress. Another action that I believed affected the process in a good way was the tuning of the mechanical end cap of the PVE's 9mm combination spanner to move the spools in and out, and I observed that the AUX valve spool was hesitant to move freely, but after many tries, it became free, and when I put the forklift on. There was pressure on every HYD hose on the forklift.
Ok ill try to help Hydraulic system pump valve cylinders flow back to tank. Try one cylinder first to see what's. NOt doing its job. Test pump psi because contamination can heat the pump weaken if psi is good the lines connect by the manual the valve is a switch gate like train station Don't guess alot people can help even the dealer but ask for technical department not service you will be. Charged.check vale in the wrong way is a headache grab a hydraulic schematic your on your way good ??
Hello Gurus, Just to add. Currently, there is no oil coming out from any of the system's main, tilt, and aux functions.
The situation is severe. I believe it can be fixed with all your assistance and contributions.
Many thanks in advance.
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