How to Repair a Hydraulic Ram Seal

Written by paul miceli Google
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How to Repair a Hydraulic Ram Seal
Hydraulic systems work under pressure to lift heavy loads. (hydraulic lock mechanism image by green 308 from

Ram seals are a vital part of a hydraulic cylinder. As pressure is introduced to a hydraulic system, the metal ram inside the cylinder rises to lift heavy loads. The ram seal acts as a barrier that keeps hydraulic fluids inside the cylinder to prevent leaks and spillages. Although they are relatively small in size, ram seals can withstand huge amounts of pressure and can last for several years as long as the cylinder is operating correctly. Any visible signs of oil leakage are usually a clear indication that a ram seal has failed.

Skill level:

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Things you need

  • Wrench set
  • Weight-bearing slings
  • Internal hexagonal wrench
  • Flathead screwdriver
  • Petroleum jelly

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  1. 1

    Release pressure from the hydraulic system by releasing all fluids back to the tank. This can be achieved by activating the pressure release button on the hydraulic valve. Check that the pressure gauge reads zero and look inside the tank while the pressure release button is in operation to check that no further fluids are being discharged.

  2. 2

    Release the hydraulic ram from the load-bearing device using an appropriate sized wrench to release the nuts. On large hydraulic systems such as passenger lifts, weight-bearing slings should be wrapped over a safety beam before taking the weight of the car. Pay attention to the position of your fingers and make sure they are clear of the cylinder because the ram will drop slightly once it has been released.

  3. 3

    Take an internal hexagonal wrench and release the two metal shoes to the sides of the ram at the entrance port of the hydraulic cylinder. Once the nuts have been removed, pull the shoes away and put them aside for refitting later. Removing the shoes should make the ram seal visible. Use a flathead screwdriver to prise it out of the cylinder, taking care not to scratch the surface of the ram.

  4. 4

    Check the old ram seal for signs of wear. A camber on the inside edge of the seal indicates that the cylinder is no longer plumb with the load-bearing device, and an adjustment should be made before a new seal is installed. Check for scratches on the inside of the old ram seal, as this indicates fluid contamination. Drain the system of old fluid, flush and add new fluids before installing the ram seal if scratches are present.

  5. 5

    Lubricate the inside of the new seal with petroleum jelly and slide it over the ram into the entrance port of the cylinder. Push down firmly to make a firm seal. Replace the metal shoes and bolt them back into position using the internal hexagonal wrench. Apply a small amount of pressure to the system using the hydraulic hand pump, which is located to the side of the hydraulic valve. Add pressure until the ram meets the load-bearing device and secure it into position with a wrench using the nuts that were removed earlier. Any weight-bearing slings used to hold the load-bearing device can now be removed.

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