The BMW M coupe comes with a warning light for oil pressure, as well as an oil temperature gauge in the center console. I’d like to know if my oil pressure drops below normal without waiting for the oil warning light to come on at 7 PSI, so I decided to install a VDO oil pressure gauge. This project involves interior trim removal and modification, wiring, and replacement of the oil sender (this last one requires you to drain the oil, so you might as well schedule this project when it’s time for an oil/filter change). As usual, Ron Stygar was a big help on this project. Thanks, Ron! His original post in the bimmer.org archives is here.
The oil pressure gauge that almost matches the existing coupe gauges is a VDO Vision gauge. I say “almost” because standard Vision gauges come in all black, but the gauges in the coupe’s center console are chrome ringed. If you don’t care about the chrome you can buy a Vision gauge anywhere, but to match the existing gauges I went to Jon Maddux at LeatherZ (www.leatherz.com). Jon sells the 0-80 PSI oil pressure gauge ($79.00) that you need for the coupe, and supplies various colored bulb covers. The orange cover makes the gauge light a very close color match to the existing gauges. For this job you’ll also replace the stock sender with a VDO dual sender with angled mounting adapter that provides both the warning light and pressure reading, and Jon offers these too ($67.00). You’ll be running four wires for the electrical connections – one for power, one for dimming power, one for ground, and one for the sender. I purchased four 10-foot lengths of stranded wire in various colors and this was more than enough length. You need #14 wire for the sender wire to give the circuit the correct impedance; the other wires can be smaller gauge. You’ll also need four crimp-on female wire connectors to make the connections to the gauge and two crimp-on O connectors for the sender connections.
Some coupe owners choose to put their oil pressure gauges in the center console, replacing the analog clock. I didn’t want to give up the clock so opted to put the gauge on the A-pillar. The gauge mounts to the A-pillar, or more accurately to the A-pillar trim cover, in a plastic housing called a “pod”. I bought a single gauge A-pillar pod from egauges (www.egauges.com), part # 240-347 ($31.13). They also sell a dual pod in case you want to add a second gauge such as outside temperature.
NOTE: all directions (forward/rear, left/right) are in reference to the driver’s seated position.
Place the pod on the A pillar trim cover and slide it up or down until you get it approximately where you want it. Mark the location of the pod on the trim cover, then remove the cover by wedging your fingertips between it and the windshield and pulling it away from the windshield. The trim cover is held onto the A-pillar with two snap-in connectors. Once the connectors pop loose, slide the bottom edge of the trim cover out from the crevice formed by the A-pillar and the dash.
Cut a hole (I used a Dremel tool with a carbide abrasive tip) in the A pillar trim cover corresponding to the opening in back of the pod.
This hole is used to route wires and to give you access to the back of the gauge for changing the bulb. If your gauge ended up right over one of the trim cover’s snap-in connectors, you may have to adjust the pod position slightly.
Insert the gauge into the pod, orient it so that it will be straight as viewed from the driver’s position, and secure it by screwing the gauge nut onto the back.
To mount the pod to the trim cover, I drilled pilot holes and used the supplied plastic ribbed pins (screws).
For power, dimming power, and ground wires, you need a sufficient length of wire to run from the gauge to the footwell area. For the sender wire, you need enough wire to run from the gauge to the footwell area, through the firewall, and on to the front of the engine compartment. Leave plenty of extra length on the wires at this point. Terminate one end of the wires with the crimp-on female wire connectors and, using the instructions with the gauge, mount each wire to the proper connector on the back of the gauge. Tape the wires to the back of the A pillar trim cover to keep them in place. Note which color wire you used for each connection.
Disconnect the battery before proceeding!
You’ll need to remove the lower dash panel just above the pedals, loosen or remove the upper dash panel under the steering wheel, and remove the driver’s kick panel with dead pedal.
Run the wires from the back of the gauge through the crack at the bottom of the A-pillar.
They will come out at the left bottom of the dash.
Re-install the trim cover/pod assembly onto the A-pillar.
Editors Note: The silver metal part with the messy looking ends is an interesting safety feature. Somewhat like a pillow, it’s a soft/thin metal with foam filling. Designed to protect your knees in an accident.
Leave some wire slack under the upper dash panel in case you need to remove the trim cover at some later date. Continue routing the wires down into the footwell area. Locate a violet/any color wire for power, and a gray/red wire for dimming power, from the existing wires in the footwell. You will probably have to release wire bundles by cutting wire ties in order to locate the colors you need. The dimming power wire allows you to control the lighting level of your new gauge by twisting the headlight button, the same way you adjust the other instrumentation.
Cut off any excess on your power and dimming power wires and splice them into the selected wires. I soldered the splices and coated them with some Star Brite liquid electrical tape. Connect the ground wire to the grounding nut, forward of the kick panel speaker. (Ground wires are solid brown in the coupe.)
Resecure all wires with wire ties. You can do a power and dimming test at this point by reconnecting the battery; just don’t forget to disconnect it again!
OK, three wires down and one to go! Take the lid off the fuse box (left rear of engine compartment) then unscrew the four #10 torx screws that hold the fuse box onto the wiring box below it. The right rear screw is somewhat obscured by the hood release cable. Just push the cable out of the way enough to loosen the screw. Disconnect the two black wire junction pods, the large red wire, and the green connector that are fastened to the right side of the fuse box and lift up that side of the box.
This will give you sufficient access to wiring box so you can see and grab the sender wire as you feed it through. You’ll see where the main wiring bundle comes through the firewall and into the wiring box. You can try to get your sender wire through the same hole but it’s already pretty well jammed with wires, so I just drilled a small hole nearby and ran the sender wire through it. Drill another hole in the right side of the wiring box; the sender wire exits the wiring box through this hole. Put a dab of silicon sealer on the hole to keep nasties out of your wiring box, and then reassemble the fuse box.
Route the sender wire along the back of the engine compartment, underneath the intake manifold, and to the oil filter, attaching it to the existing wire looms with wire ties.
Now it’s time to drain your oil and remove the old filter insert. Remove the air intake box to allow room to reach the oil sender. Unscrew the old sender from just below the oil filter and cut the wire attached to it, leaving as much length as possible. Terminate it, and the new sender wire, with O-connectors.
Mount the new sender to the angle adapter. Hand-tighten the sender to the adapter until snug but don’t over-tighten. The sender has tapered threads that do not require excessive torque to achieve a good seal. Align the sender so that the connector posts on the top are perpendicular to the engine-mounting hole on the adapter. Install the adapter/sender assembly in place of the old sender. Caution – improper installation of the oil adapter can damage your engine and cause oil leaks. Tighten the adapter bolt to 35-40 NM.
Connect the old (alarm) wire and the new (pressure) wire to the correct posts as marked on the top of the sender.
Replace your filter insert and oil, reconnect your battery, start your car, and check out your new gauge. Under normal operation you’ll see a range of around 15 PSI at idle to 58 PSI. Assuming everything works, replace your interior panels, and you’re done!