Oil Leak

[Makai]

Hello A4rians!

I'm new to the family. I purchased 79' Cat 27 with Atomic 4 engine a month ago. It has a serious oil leak that I find out. It leaks only when the engine is on. I took a video of it. I'm new to this engine and don't know the parts. I checked the engine manual from moyer marine and it looks like oil pressure adjuster. Can you help me finding out the problem part and how to fix? I'm sure there are threads about this problem and I don't know how to search for the title. Please Help! Thank you

Video link: https://youtube.com/shorts/Zg1bEYI3ano

[Dave Neptune]

First welcome to the MMI Forum.

Looks like a sender possibly. Is the narrow end an electrical plug or a slip fitting?

The oil pressure sender is usually mounted on the flywheel end. It could also be an oil pressure switch for an electric fuel pump if so equipped.

It is screwed in at an oil galley access port. All we need to do is figure out what it is for if it is a sender. If it is a slip fitting for tubing it could of been hooked to a mechanical oil pressure gage.

It can be replaced with a standard NPT pipe plug to address the leak, then you can figure out what it was for later. Use a bronze plug if you can although any NPT plug will work temporarily.

Dave Neptune

[Sam]

A year ago a friends 77 A4 had a serious leak when engine was running. Trace it to a blown oil pressure switch screwed into the block [ lead going to fuel pump] just by carb. Took to local auto parts store nearby for replacement.

[Al Schober]

Most of the old f..ts on this board are visually oriented and like pictures - me included. A picture of where the oil is coming from would really help.

[Makai]

Problem Solved

Hello All!

Thank you for the brilliant support and tips. I figured it is the Oil pressure sender unit leaking and replaced with a sierra oil pressure sender unit bought from west marine. it worked. I made a video as well to explain better.

Video Link: https://www.youtube.com/watch?v=3IMVlKVKFdM

Thank you again for the support. My next project will be checking the compression on pistons.

[Al Schober]

I don't think you're there yet. Looks like you've stopped the leak, but have replaced the OPSS (safety switch) with a sender unit. Sender unit will NOT work as a safety switch! Electric fuel pump won't work properly.