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How I replaced the oil pressure sender switch (Not-a-mechanic edition)

1979 Views 6 Replies 4 Participants Last post by  Joey_Twowagons
with head, oil filter, and accessories removed
Hello all,
Yesterday, I replaced the leaky oil pressure sender switch on my 99' Ford Escort ZX2. This is just my one-time experience and what worked for me. I didn't remove the starter or anything. Hopefully this will save others some time and headaches.

One random day, I checked my oil and it was only as high as the very bottom of the dipstick where it says "ADD." It was low, but the oil light on the dash never came on. If I added oil, it would just leak out all the new oil to the point explained previously on the dipstick. It would also leak a bit more if the car was not on a flat angle. The drip appeared to be coming from the drain plug of the oil pan.

How I found the leak:
Brake cleaner, Oil UV dye, and blacklight. If you expect to use this method outside on a sunny day, be prepared to wrap the front and the sides of the car to block the sunlight. Otherwise, you will not see the dye clear enough.
Sky Purple Hood Automotive lighting Violet

  • 1/2" ratchet ( or 3/8" ratchet and a 1/2" adapter etc. ). There is a metal tube in front of the sensor. I couldn't manage to get any pliers near it. Would recommend a flexible ratchet. But a fixed one also works.
  • 2" extension.
  • 15/16" 6 point deep socket. A common socket set will not have this large of a socket. I would recommend a non-impact type of socket because they are heavy and become unwieldy in this situation.
  • Teflon/plumbers tape ( if you opt to use it. )
  • Needle nose pliers.
  • Jack stands*, gloves, eye protection, etc.

You can reach the sensor somewhat from the top of the engine, but mostly from below. From the top, if you look directly down, between the cables of the acceleration linkages, with a light you should see the sensor on the back of the engine. You can reach around the alternator with your left arm. However, the space there is very limited. If you have flexible tools, smaller arms, that might work for you. I removed the electrical connection of the sensor from the top that way. The overall struggle I had with replacing this sensor was mostly the limited view. Being able to see what you're trying to work on at the same time. Where your arm needs to go, your head also needs to be there too to see anything. But you can get more of a view and manage a ratchet etc. from the bottom.

  1. Remove the electrical connector from the old sensor. The sensor has threads on top, and you'd think it would screw on but it just pulls off and presses back on. I used a pair of needle nose pliers from the top of the engine. With a good grip and slight wiggle, it should come off fairly easily. Push the connector out of the way for the socket.
  2. From the bottom, remove the old sensor using the ratchet, extension, and socket. I found it easier to put the extension and socket on the old sensor. Then the ratchet onto the extension. There is an annoying metal hose in front of the sensor. I had to work the socket kind of above that hose where there is more room and come down to the sensor. No oil leaked out, but be prepared for a bit to.
  3. Install the new sensor.
    • The new sensor I received had something of sealer on the threads. I put teflon tape on it anyways.
    • I was unable to install the new sensor from the bottom. Given that metal hose in front, I could not fit the deep socket - now with the sensor in it - in that small space. With the lack of view, I could not get the thread started and my arms began to burn out. I took a different approach.
    • I took my smallest 1/4" socket and put the sensors threads in it. Then held the two together temporarily using electrical tape. The idea was to use that on a thinner and lighter screwdriver just to get the sensor started. From the top, I was able to go around the alternator and get the sensor threaded easily. Then I pulled off the 1/4" socket along with the tape. You can get creative or just use any stick really.
    • From the bottom, finish screwing in the sensor with ratchet. I took the spark plug approach; snug, then another quarter turn.
  4. Push back on the electrical connector and test for leaks.

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sweet write-up. I'm going to move it to the how-to section.
Good write up, but I'd recommend not adding teflon tape to the sender that already has sealer on it.
They make a special socket that fits oil senders, it's a little bit shorter than a deep socket so might help when space is tight.
Good write up, but I'd recommend not adding teflon tape to the sender that already has sealer on it.
They make a special socket that fits oil senders, it's a little bit shorter than a deep socket so might help when space is tight.
I did not trust the sealant given what I found on the old sensor. The threads were dark and I was tired and frustrated. I probably should have taken a wire wheel to the before the tape. Currently, it hasn't dripped a drop on the driveway. I'll have to check up on it in some time and report back.

I know first hand the convenience those sensor sockets offer. (upstream o2 sensor... yeesh!) But I was unable to find the correct sized one locally. All they had at O'Reillys and AutoZone were several sizes too large. If anyone has experience there, the size or diameter of the socket, would be good to know?
I changed out mine when I replaced my head gasket. It was really easy to replace with the head off!
I changed out mine when I replaced my head gasket. It was really easy to replace with the head off!
The very first pic in the OP was a screenshot taken from a youtube video where the dude happened to have the head off. I guess they were just making an informative video. I really tried to find it again, to link here, but I was not able to find it.

This post was about how to replace it without taking anything off. I think there is another thread on these forums saying to remove the starter. It surely can be done without all that.
Yes, it can be done from underneath without taking out the starter. It's true you can't even see what you are doing, but that's not unusual in car repair. You have to go by feel.

On my car I took the sender out and put in a tee fitting to refit the sender and add an oil line when I was diagnosing why my oil light was coming on. I removed a battery terminal to be safe working around the starter.
I believe I used short wrenches and it was not easy.
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