Oil Pressure Sender

Difficulty: 1/5

Time to install: 45 mins

Tools Required:

    • 24mm deep socket with extension to remove OEM sender

    • 17mm open wrench for the new sender

    • Sensor Safe RTV Silicon

    • Wire Stripper, Crimper, 18-gauge ring terminal and spade connector

    • Thread Locker (Loctite)

    • Rag to clean up oil

This is involves taking out the the old sender, screwing the new one in, and swapping terminal from a sliding, M-disconnect to a ring terminal connector. I got the basics from Sheldon Stoke's website and have added some additional research.

Selecting a Pressure Sender

There are a variety of oil pressure sender brands, but I chose VDO. The Miata requires an oil sender with a threading of 1/8-28 BSP (British threading standard, as opposed to NPT). The majority of senders only come in 1.8-27 NPT, so before we go on, here are the main requirements:

    • Sender with 0-80 PSI measurement, 5 bar, 10-180 ohms (larger PSI ranges will provide less accurate readings on the Miata cluster)

    • Threading of either

      • Common: 1/8-27 NPT with threading adapter - approx $20-30, plus $4 for the adapter

      • Rare: 1/8-28 BSP - approx. $70 - sometimes still available at old Porsche specialists

    • Optional - Low Pressure Warning terminal (extremely rare on 1/8-28 BSP senders)

The differences between either is small. A direct fit without adapter introduces another chance for an oil leak. Many run with the adapter, no problem. I chose the more expensive option, because - well, I was amazed I could find it. Probably not even made anymore. I also got the low pressure warning terminal, but it won't be covered in this article. If you're concerned about leaks and the weight of a large sender on a long-ended adapter, look up remote oil sender lines on eBay. It's just a long line so you can mount the sender somewhere else, away from any vibrations. Not expensive, either.

VDO Senders are available at places like (in no particular order):

Parts list:

    • New VDO sender (and adapter if desired)

    • Crimp ring terminal

    • Male spade connector

    • 2" 18-gauge wire

I already created the adapter. It's just a small piece of wire about 2" in length with the quick disconnect on one side, and a ring terminal on the other. Way easier than trying to crimp under the engine. The black stuff on the ends is liquid electrical tape. Optional, but a very nice item to have if you have lots of wiring projects.

Raise the car on ramps, or jack stands, or from what I hear, driving the Miata up on a curb will work, but just make sure to turn the wheels all the way to the left to get some crawl space.

This is a pic of the original sender near the oil filter. Just behind this (meaning towards the firewall) is the oil sender. You're looking at that little metal bolt with the wire attached to it, sort of looking like a spark plug.

Pinch the plastic sender harness and pull. It should slip off with some wiggling.

It was difficult to remove the sensor from underneath the car, but I was able to use an extension and work from the top with the 24mm socket. Removing it was a bit tough. You can use a breaker bar, or put a pipe on your ratchet to lengthen the handle and give you more leverage. Remember, turn counter-clockwise!

Once the sensor was loose, I went back underneath and with a rag, I unscrewed the rest by hand. This allowed me to catch the small bit of oil as I was unscrewing the sensor. Very, very little oil should come out here.

Depending on the new sender, and if it has the warning post, you'll attach the new wire to the post that says "G" (gauge) or "S" (sender). "WK" or "WL" is the other post for the warning light. I'm not going to screw the cap on the other post, as I want to keep it for later use.

Apply a thin coat of your chosen, oil-resistant RTV silicone on the new sender threads. Leave the first few threads to have direct contact for a good ground. Otherwise, you might get a poor signal to the gauge!

Screw the new one in! Honestly, here I cheated and tightened it by hand and skipped the 17mm open wrench, but if you can do it, go for it. I don't know what you should torque it to, but I honestly don't have a clue as to how anyone could get any tool small enough to get under that huge sensor. I just tightened it as much as I could. Use the rag to clean up any extra oil drips, it'll help to notice any drips that follow from leaks.

Attach the existing wire to your new wire adapter. All done! Turn on the car, and check that your pressure gauge engages immediately. If it doesn't, turn the car off immediately. If it's working, run it, and give it a little gas. Then check for any oil leak. Take the car out for a spin, then check for oil leaks again.

Final Notes

The needle position on your stock gauges will be different with the new sender. Optionally, you can open your gauge cluster and reposition the needles if you choose (it's quite easy). Without the needles repositioned, these are the positions I have noted, though differing oil temperatures will make a difference as can the sender:

  • Hot engine at idle: Needle is just above the first tick mark

  • Engine at full throttle: Need at second tick mark