Cleaning the hydraulic system of small four-wheel tractors requires systematic operation to remove impurities, residual old oil, and sediment-key to avoiding component wear and ensuring stable operation.
1. Pre-Cleaning Preparation
1.1 Safety & Tools
Safety: Shut down the engine, return the hydraulic control valve to neutral (release residual pressure), and wait for oil to cool down (avoid scalding).
Tools: Wrench (for drain valve/filter), oil pan (≥10L), clean rag, soft-bristled brush, diesel oil (for flushing), new hydraulic oil (matching specification), new oil filter element.
Tractor Preparation: Park on flat ground; clean the oil tank cap, filter surface, and pipeline joints to prevent dust from entering during disassembly.
2. Step-by-Step Cleaning Process
2.1 Drain Old Oil Completely
Open the hydraulic oil tank's bottom drain valve (or plug), place the oil pan under it, and drain all old oil (about 10–15 minutes until no continuous flow).
Disconnect the oil return pipe from the tank, place the pipe end in the oil pan, and start the engine for 5–10 seconds (only idle, no load) to drain residual oil in the pipeline/pump (avoid long startup to prevent pump dry grinding).
2.2 Clean the Hydraulic Tank
Tighten the drain valve, pour diesel oil into the tank (10–20% of tank capacity) as a cleaning agent.
Cover the tank cap, start the engine, and run the hydraulic system at idle for 1–2 minutes (operate the control valve gently to circulate diesel and flush the tank inner wall/pipeline).
Shut down the engine, open the drain valve, and drain the diesel oil completely (diesel will carry away most suspended impurities).
Use a soft-bristled brush and plastic scraper to scrub the tank bottom and corners (remove stubborn sediment); wipe the inner wall with a lint-free rag until no oil stains remain.
Leave the tank opening and drain valve open for 5–10 minutes to let residual diesel evaporate (avoid mixing with new oil).
2.3 Clean/Replace Filters & Key Components
Remove the old oil filter element (disposable type) and replace it with a new, model-matching one; for detachable suction filters, clean thoroughly with diesel (refer to previous filter cleaning steps) and air-dry.
Disassemble the pressure relief valve and one-way valve, soak them in diesel for 5 minutes, scrub with a soft brush to remove impurities, and blow dry with clean air (ensure valve cores move flexibly).
Wipe the hydraulic pump and valve body surfaces with a clean rag; check for loose mounting bolts and tighten if necessary.
2.4 Flush Pipelines (Optional for Severe Contamination)
If the system has severe contamination (e.g., metal particles), connect a temporary flushing pipe between the pump outlet and tank inlet (bypass the cylinder/valve).
Pour flushing oil (low-viscosity hydraulic oil or diesel) into the tank, start the engine, and run the pump at idle for 10–15 minutes to flush the pipeline.
Drain the flushing oil completely and reinstall the original pipeline.
2.5 Refill New Oil & Bleed Air
Close the tank drain valve, install the new filter element (apply oil to the gasket for sealing), and refill new hydraulic oil (meet manufacturer's specification) to the standard level (between MAX and MIN, close to MAX).
Close the tank cap, start the engine at idle, and operate the hydraulic control valve repeatedly (lift/lower attachments 5–10 times) to bleed air from the system.
Open the tank cap to check for foam; continue bleeding until foam disappears, then recheck the oil level and supplement if necessary.
3. Key Notes
Avoid Contamination: Use only clean tools and diesel; ensure no dust, lint, or water enters the system during cleaning.
Do Not Damage Components: Do not use metal brushes or hard scrapers (scratch tank inner wall/filter screen) or over-tighten bolts (damage gaskets).
Cleaning Cycle: Perform full-system cleaning every 2–3 oil changes (or when oil has severe contamination, e.g., metal particles, milky white water mixing).
Post-Cleaning Inspection: Run the tractor with no load for 10–15 minutes; check for oil leakage, abnormal noise, or overheating to confirm the system operates normally.
