The Proverbial Oil Pressure Sending Unit Leak

After wiping down the whole engine block a few weeks ago, I notice this morning that a fine film of oil is covering the front left of the engine block and all the components around the oil filter. I start feeling around and under components and when I reached down under a little domed looking thing near the oil filter I felt liquid on my finger which smelled like oil. I decided I had better find out what this little thing with a wire coming out of the end is and how to fix what must be a very slow, but persistent oil leak that is getting sprayed by the air from the fan and covering Old Blues front left engine block in a fine coat of oil.

I look up the engine in the shop manuals and find I am looking a the Oil Pressure Gauge Sending Unit. A single adapter with both the oil pressure gauge and the warning (idiot) light sending units mounted on it.  The adapter sticks up from where the oil filter connects to the oil pump and has two holes, one for a round button looking unit with a simple flat connector and the other looks kind of like a canister with a round female connector plugged into the end. Both screw into the adapter and I think this may be the source of my drip. 

From the FE Forums I find Bill mentions numerous times that "The oil pressure gauge sending unit is notorious for leaking and getting gummed up with dirty oil. Once this occurs, the little charmer no longer works. Note: When there's an oil pressure gauge and an oil warning (idiot) light on the dash board, there are TWO sending units, both thread into an adapter (C5TZ-9B339-B) that threads into the engine block.

The oil pressure sending unit is much larger (has a domed head) than the oil warning light sending unit."

E4ZZ-9278-A (replaced: B7T-9278-A, C7ZZ-9278-A & C9ZZ-9278-A) .. Oil Pressure Sending Unit-Use with Pressure Gauge (Motorcraft SW-1547B).

B6AZ-9278-B (replaced B6A-9278-B) .. Oil Sending Unit-Use with Warning Lamp (Motorcraft SW-667)."

I pulled the domed unit by pulling the post connector and tucking the little wire out of the way, then getting a wrench on the square brass block above the threads. I removed the sending unit (this one's for the Oil pressure gauge), and while it was off the engine I removed as much of the blue paint as I could. I presume whoever painted the engine block when it was rebuilt also painted the oil pressure sending units. I then wrapped the threads with teflon tape ensuring the thread edges were exposed for grounding and remounted the unit into the adapter.

I drove around yesterday in the unusual spring like weather and when I got home took a look (and feel) at the unit. No leaks and my now wiped down engine block was oil free.