This is one of our long term customers cars which we’ve performed numerous jobs on including a Walnut Blast. He contacted us as the car had displayed a low oil pressure warning on the dashboard. Generally speaking if a car tells you the oil pressure is low, damage has often already occured. The customers hunch was that it was just the sensor. He’s a clever man so I agreed that we would replace the sensor. On later models you can actually read the oil pressure, but on this model it just has a sensor connected to a warning.
The N47 Oil Pressure Switch: BMW’s Little Hidden Joke
If you own a BMW 520d with the N47 engine, you already know it’s a clever piece of engineering — strong, efficient, but also difficult to work on and with numerous weak points. The sensor is located in a hard to access place, but how hard could it be?
Famous Last Words
Armed with optimism, a 24mm socket, and the false confidence of several YouTube tutorials (all apparently filmed on different engines), I popped the bonnet.
“Ah yes,” I thought, “it’ll be right there by the oil filter housing…”
Except it wasn’t.
After several minutes of staring into the engine bay like a confused meerkat, I accepted the truth — on this version of the N47, it’s buried halfway down the side of the block, somewhere between the oil cooler and a collection of hoses. Only by taking a photo with my camera was I able to see it.
Firstly I tried outside before putting the car on the lift, access denied, the internet said access was easy from underneath, with the car raised on the lift it was also impossible to see or reach, unless you have the head of a toddler and the arms of Mr. Tickle.
So the job has to be done by feel alone, removing the electrical connector is the first step, then with a 24mm deep socket you can get on the sensor and remove. If you’ve ever worked on cars you’ll know how much harder things are when you cannot see what you are trying to do.
New sensor in, torque to 25 Nm (ish, because who can actually get a torque wrench in there?), plug reconnected, and… success! Oil light gone, no leaks, no tears, just a few cuts on my arm..
Wondering what’s inside it and how it works? Worry no more…
A flat tyre that you keep inflating?
With the sensor fixed, a road test revealed a flat rear tyre. Only 10 PSI. Once pumped up it lost 10PSI overnight, the tyre passed visual inspection, we suspect it is leaking around the bead – usually alloy wheels corrode on the inside edge.
Cue two new rear tyres and the wheels being cleaned of corrosion on the inside edge to ensure a good seal.
If you have a problem with your BMW or any other car for that matter, give us a call or email and we will help !
