I am in the process of setting the oil pressure down on my right engine and have hit a small snag. My relief valve is the kind that requires washers or spacers to adjust the cap or spring length to exert more or less pressure on the ball and seat, not the screw in or out type. The cap normally takes an an900 crush gasket as a seal and now I have to install a spacer (looks like a big washer) and a crush gasket. What I am concerned about is there is no seal between the spacer and the crankcase housing, only between the cap and the spacer. I don't think two crush gaskets, one on each side is correct and the manuals don't provide any guidance. The spacer should seal ok but I don't want to find out the hard way that it doesn't. Does anyone have experience with this or a contact that might have an answer? Thanks for the help.

Steve Von Gruben

You just add (or remove) spacers inside the housing, not on the threaded portion so no extra crush gasket. If you are trying to lower pressure you would be removing spacers, not adding them. Make sure to inspect the ball and seat when you have it open. If it's not seating properly you'll have issues. You could also have an issue with the spring itself.

I would first confirm your pressure readings with a separate mechanical gauge to confirm your readings on your gauge in your panel.

Always run the engine after the change and leak check to make sure you don't have a new problem on your hands.

Edit: Here's a video that illustrates. http://www.eaavideo.org/video.aspx?v=1687375685001

Tim

Hi Steven,

If you have removed the shim washers from under the spring, you can also replace the spring there are several different strengths available.

Failing that I have seen installations where there are two AN900 copper gaskets along with the oil filler tube gasket used in an IO540. One on each side.

Clarence

 

Thanks gentlemen for your replies and link to the video. The parts book calls for one specific part number spring for the engine and the overhaul and maintenance manual calls out a part number for the external spacer. I have checked the wire diameter and the spring compression strength as called out in the maintenance manual and spring is exactly in spec. I am aware of how to increase pressure by adding or subtracting washers but my cap doesn't have any washers in it so none to remove. The external shim is the correct way according to the maintenance manuals to decrease pressure. I will check the pressure with a calibrated external gauge and leak check. I believe the correct answer to the initial question is the spacer goes under the head of the cap and the crush gasket goes against the engine case but I was looking for independent verification since the manuals don't provide guideance.

Steve