Oil Pan Temp Sensor Thread! For a Gauge Install
 

Hey guys,

Been searching a while trying to see if there is a reference online for what size of thread the cold start assist oil temp switch uses. Also I have some details below that may help others.

I am installing oil pressure/temp gauge and also a coolant temp gauge:

-Oil pressure is coming from filter pedestal adapter by Franklin Engineering (it has a boss for oil temp but the temp sensor from my Innovate MTX gauge doesn't fit well there)
-Oil temp I plan on getting from the oil pan by replacing the cold start temp switch with an adapter that is drilled for the female pipe thread of the new sensor.
-Coolant temp will come from a similar drilled out adapter on the water pump housing. The original temp sensor installed here is a M16x1.5 (straight thread!). So If you get a M16x1.5 plug (that uses a crush washer), you can drill it out to install the gauge temp sensor. 1/8NPT.

Finding the replacement plug for the oil pan is the last piece of the puzzle. I recall it is a pipe thread but unsure of the size... I think it is a Metric british pipe thread.

Here is a picture of it, but no thread size!

https://www.rx7club.com/1st-generati...er-one-873590/

Cars in storage so I can't check it! Anyone have the sensor lying around or a 12A or 13B oil pan handy ?!

My guess is it is a 1/4" BSPT thread. That is one size up from 1/8 and has an outside diameter of ~12.3mm.

Ya I know what you mean. I just don't have access to the car right now so can't figure it out.

What I did get from Amazon that I find super helpful are these:



Takes any guesswork away from figuring out fastener specs, at least for straight thread.

For the water neck on a 12a or early 13b, this adapter works.
https://www.threadtoolsupply.com/alu...m16-38npt.html

For oil temp, an adapter for the filter pedestal is more common than messing with the pan and it will give you the temp of the actual oil traveling through system, not the oil splashing around below. I think the pan location will give you false readings in left hand corners on a track as well. I know I had to disconnect the other sensor because it was going off at two spots on my local track driving me nuts...I have included a baffle between my oil pan on my new build to help with that.
http://www.racingbeat.com/RX7-1975-1...tem/11803.html

I agree with chuyler. Oil pan is a terrible spot for an oil temp sender. I recently gave my reasons why here: http://www.ausrotary.com/viewtopic.php?f=4&t=251365

i had an oil temp sender installed where the oil level sensor usually sits. It was hopeless. Going back to oil level sensor and the oil temp sender in a pedestal under the oil filter.

Ok good advice! I figured the oil pan would provide a decent oil temp reading, of course not counting the temp drop across the oil cooler! My car is just driven on the street with the occasional track day (maybe!) so I don't have a big emphasis on oil temp. I run the factory front mount oil cooler with a 3-row radiator so don't anticipate much cooling issues.

The reason I was going in that direction is the oil temp thermistor that came with the Innovate MTX gauge and the compatibility with the Franklin Engineering oil filter adapter.

The thermistor is too long to fit properly in the provided 1/8 NPT port.

Pic below is my current workaround. The adapter also comes with a 1/4NPT port on the un-filtered side so I am using an 1/4 to 1/8 NPT adapter.

I am not too keen on how far the thermistor sticks into the oil passage. I will try and find a pipe thread adapter that spaces it out further. Currently sits ~5mm into the passage.

https://cimg0.ibsrv.net/gimg/www.rx7...0a1c6b658a.jpg

Once you add teflon tape or pipe dope to the threads the length will probably be fine.