What Are The Different Valves, Their Purpose and Operation.

Depending of the requirement of the filter for an engine it may contain one or a combination of filters. Here we explain the different valves their purpose and operation.

#oil filter

What is an anti-drain back valve?

A relief valve is located within a filter.

How it operates
  • An ADV (made of Silicon or NBR) provides a seal between the element and the inlet holes on the baseplate.
  • When engine is stopped: ADV is closed. Oil cannot drain from filter.
  • When engine running: Oil pressure opens ADV and oil passes through the filter.
  • Keeps the filter full of oil when the engine is switched off.
  • Ensures a quick flow of oil to engine on start up.
  • Prevents oil draining out from the filter’s inlet holes.
  • Stops oil from draining out of filter and oil galleries when the engine is shut down.
  • Ryco ADV’s feature a ‘cupped central section which acts like a hinge and requires the outer circumference to stretch to reach the open position.
  • An o ring incorporated in this edge regulates the valves to return to closed position.
  • Not all filters require anti drain back valve due to the construction of the engine.

What is a relief valve?

A relief valve is located within a filter.

How it operates

Allows oil to bypass the filter if it is blocked or if the oil is particularly thick, which happens when an engine is cold.

  • If the filter clogs, it opens up to allow unfiltered oil to bypass the filter and ensure continued engine lubrication.
  • Normally remains in the closed position because the oil flows through the filter media and the oil is effectively filtered and cleaned.
  • Some relief valves are built into the engine block, therefore some filters don’t contain a relief valve. Alternately some filters may contain an up-front relief valve.
  • Competitors may use small relief valves which may not allow the correct flow of oil to the engine when the valve is activated.



What is an anti-syphon valve?

A relief valve is located within a filter.

How it operates
  • Activates as a result of oil pressure change.
  • Prevents oil from draining out from the filter outlet.
  • Required for applications where the oil filter is mounted in a horizontal or inverted position.
  • Prevents oil from returning to the engine when switched off.
  • Located within the filter on the outlet side (downstream).
What is a by-pass valve?

This is not a filter valve and is located on the engine block. Also referred to as a pressure regulation valve.

How it operates

The valve will open allowing oil to flow into the engine.

  • Should the filter become blocked the valve allows oil to bypass the filter if the filter is blocked or the oil is exceptionally thick (high in viscosity) when cold.
  • Sometimes referred to as a safety valve.


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