Over the past week I found oil dripping from the right cam cover below the pressure sender unit, which was very wet around the base. Then the OBC began flashing "sensor failure" messages, along with momentary heart-stopping 0 psi readings on the oil pressure gauge.
I searched this forum and found several references to similar situations, usually concluding with the dealer or indie replacing the unit. I purchased a sender from my indie ($55) and set about replacing it myself, as I wanted it done before the weekend. Here is what transpired:
1. The oil sender unit is located forward on the right side of the engine. In the first photo you can just see it behind the A/C hoses. The second photo is a closer view.
2. The base of the sender unit has a 19mm hex, and it was immediately apparent that a standard combination wrench of that size would never work in the space available (with the engine in place.) Thinking a crowsfoot wrench might be the answer, I headed to the local tool store. (For those in this area, Pat's Tools on El Cajon Blvd in El Cajon, CA, is a great resource for new and used tools of every kind.) The shank of a crowsfoot doesn't clear the base of the sender unit, so the counterman in the store went digging through boxes and bins for something that might work. He showed me the tool in photo #3, which I thought had definite possibilities, if I opened the end to the black mark so it would slip onto the hex from the side. It is 3/4", same as 19mm, and the 12-point fitting would facilitate working in a narrow confinement. They charged me $3 for the tool.
3. Back home, a few minutes of Dremel magic and a file to smooth the edges, I had a compact open-ended wrench that slipped onto the sender's hex. Photos 4 & 5.
4. I pulled the wires from the sender unit and, working by feel alone, with the tail of the wrench in the space towards the rear of the engine, easily (perhaps too
easily) loosened the old sender and unscrewed it by hand. Replacing it with the new unit (which comes with a new sealing washer fitted,) I was able to get enough leverage for a secure mounting. I re-attached the wires - note: one wide and one narrow terminal, and cleaned off the dirt and oil around the base with a rag. Photo #6.
5. Ignition on, started the motor: normal readings on the oil pressure gauge, and a flashlight in the engine compartment to check that no oil was spraying around; so far, so good! My forearm wasn't entirely unscathed, however, as those tight confines have several hose clamps and other painful protrusions.
6. Like most enthusiast Porsche owners, I have been blessed with the necessary OCD, so, removing the right rear wheel, I proceeded to take off the coil shield and clean away as much of the accumulated oily crud from the cam covers and surrounding area as I could. It seems that the sender unit had been seeping for a while before the dripping made it apparent. After putting it all back together and doing a couple of hundred miles this weekend with no OBC messages, the bottom of the motor is bone dry!
I hope this DIY proves helpful to someone who, now or in the future, may need to replace the oil sender unit -- it doesn't require a Porsche shop or $400 P-tool to do the job. If a regular Rennlister needs it, I'll be happy to loan them my "priceless" tool. PM me.
P.S. Southern California + Early Summer + 911 Cab = HEAVEN!