Top Hydraulic Pump Restoration
Short answer: Use the correct fluid. The Fisher Body Service Manual specifies Dexron II automatic transmission fluid (hydraulic jack fluid is also a good choice).
Do not use: standard hydraulic fluid (it foams and is too viscous — it can burn out the pump motor), or brake fluid (it attacks and breaks down the rubber seals — brake fluid belongs only in brake systems).
To flush the old fluid properly, take the lines apart and stroke the cylinders. AMES sells a fill kit (container, hose, special reservoir end, instructions); you can also assemble your own.
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Content last modified: June 13, 2026 at 10:06 am
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