Self Sealing Clamp On Adapter Installation Guide
For Lycoming Engines

Installation Procedure for Self Sealing Clamp On Adapter, Lycoming Engines

Lycoming engines typically have one plug in the accessory case, which can be removed and replaced with a hose fitting. If the plugged port is unavailable there are three possible solutions for installing a drain port. The first, which is the most labor intense, would be to remove one of the oil return lines from a rear cylinder and modify it by welding an additional piece of tubing creating a "Y" connection. The second would be to remove a cylinder rocker cover, drill a hole and weld fittings in place as described in the Installation Guidelines for the RMJ-AERO oil separators. The alternate method is the use of the RMJ-AERO Self Sealing Clamp On Adapter. The only requirement for this installation, is drilling a 1/4" hole in the oil sump filler neck. The stainless steel clamp provides a return port connection to the oil sump using a single bolt for attachment and sealing. The silicone cushion material is oil and fuel resistant and rated for -120° F to +450° F temperatures.

L103 Self Sealing Clamp On Adapter for Lycomings

Apply RTV Sealant To Inside of Adapter

Adapter In Position On Lycoming Filler Neck

"Y" Connection Welded In Cylinder Oil Return Line
Click on any picture to see a close-up.

  1. Read all instructions before beginning installation.
  2. Note: Your separator must be mounted as high as practical in the engine compartment and in a position which is easy to connect to the engine breather line.
  3. Determine a location on the oil sump filler neck, which will provide downward slope drainage from the oil separator return line. You must take into consideration the connection at the adapter, as it will require a small hose clamp, and access space needed. There must be NO interference with any other engine plumbing or controls.
  4. Once the position has been determined on the filler neck, use a center punch to mark the location for drilling the 1/4" diameter hole. (DO NOT DRILL THE HOLE YET!)
  5. Remove the oil sump filler neck by removing the safety wire and unscrewing the neck from the engine.
  6. Drill the 1/4" hole thru the filler neck wall in the location marked while mounted to the engine.
  7. After drilling the hole, inspect the inside of the filler neck tube for any burrs that may still be attached to the tube. Remove them with a small rattail file and clean the inside of the tube before reinstalling it.
  8. Trial fit the Clamp On Adapter with the filler neck tube and make sure the hole drilled is large enough to accept the 1/4" diameter tube projecting from inside the Adapter. If the hole is too small for the tube to go into, enlarge it as required, but not too large. Remove the Adapter prior to reinstalling the filler neck.
  9. Reinstall the oil sump filler neck and safety wire as was required. The drilled hole will now be in the desired location for the Adapter.
  10. Thoroughly clean the outside of the filler neck tube in the area of the drilled hole with solvent that will remove oily deposits. Apply a "small" bead of Permatex Silicone Gasket Maker, Ultra Blue No-Leak RTV Silicone around the outside of the tube projection and on the silicone cushion of the clamp (see photo above). Note: Ultra Blue is much more oil resistant than ordinary silicones. Ultra Blue offers excellent adhesion to oily surfaces. Contact with oil increases flexibility and seal. It is non-corrosive and has a low volatility. Temperature range is -95° F to +400° F.
  11. Now install the Clamp On Adapter by inserting the 1/4" projecting tube into the hole drilled in the filler neck. Hold in position and secure with the AN bolt, washer, and nut supplied. Your oil return port is now ready for connection to your oil separator.
  12. Connect the separator drain to the Clamp On Adapter port using oil resistant tubing. We recommend silicone tubing, which can handle elevated temperatures. Remember this is not a pressurized line. It is very near atmospheric pressure during operation. If you cannot find silicone tubing locally, contact RMJ-AERO. We stock 1/4" tubing and can cut any length required. (Current prices can be found on the Prices & Warranty page.) Use Aero-Seal and or Breeze Miniature hose clamps for installing all separator hose connections.
  13. For additional information, read about oil separators in Tony Bingelis's book "Tony Bingelis On Engines", available from the EAA and other sources.


[RMJ-AERO Main Page] [Oil Separator] [Custom Fabrication Services]
[General Installation Guide] [Separator Maintenance] [Aerobatic Elbow]
[Continental Installation Guide] [Continental Clamp On Adapter Installation Guide]
[Lycoming Installation Guide] [Lycoming Clamp On Adapter Installation Guide]
[Prices & Warranty] [RMJ-AERO Gallery]

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