Use of the solid brass swivel fitting allows the owner to unscrew the oil filler cap without twisting the return oil line from your Frantz Oil Filter. While the fitting may be used in other locations, we will concentrate on using the oil filler cap as the point of return for the oil supply to return back into the engine from the Frantz Oil Filter.

The tools required for this installation are a drill motor, 3/8” drill bit (or optional 5/16: drill bit and 3/8-24), and 9/16” wrench.

Be sure to check for sufficient clearance under the hood for the extra room the fitting will require when installed. While it only adds ¾” to the height of the filler cap, any additional hose fittings and the hose will increase the required clearance. Keep in mind that a hose must be safely routed and attached to the fitting. Make sure there is sufficient internal clearance for fitting inside the oil filler cap and no internal components that will come in contact with fitting.

As a safety matter, please do not work on equipment that is running or still hot. Avoid burns and allow equipment to cool down before working on it.

Installation requires drilling which will produce metal or plastic fragments. Be sure no fragments get into the lubrication system. I recommend removing the oil filler cap from the engine before drilling on it. Then, before re-installing it, clean it thoroughly to remove all metal or plastic fragments.

Now, here is the step-by-step process for a typical fitting installation in an oil filler cap.

There are two choices when drilling through the center of the oil cap. The first is providing for a tapped hole while the other way is a simple through-hole without threads. Both work well.

For a tapped hole, drill a hole with a 5/16” or letter Q drill bit. Thread the hole with a 3/8-24 tap. Put sealing washer on male thread of the fitting and screw the fitting into the hole tightening securely. The locking nut is not necessary but may be used if desired.

The following photos show the through-hole process. First, drill a hole with a 3/8” bit. Put the sealing washer onto male thread of the fitting and push the swivel fitting into the drilled hole. Screw the self-locking nut onto the fitting and tighten securely.

Install a 1/8”NPT hose fitting to the outside of the swivel fitting using a 9/16” wrench to hold swivel portion of fitting from turning.

Attach the return oil line hose to the fitting. Re-check hose routing to be sure it will not come in contact with moving parts or hot surfaces. Start engine and check for oil leakage at fitting.

Tighten fitting as necessary.

Here's the finished install. Note, a 90-degree elbow was used to facilitate clean hose routing.

P.S. This swivel procedure is not recommended for Dodge trucks with 6.7L Cummins engines with ratcheted oil filler cap. Other smaller Cummins engines are okay.