I did this same thing a year ago but for a coolant pressure sensor, works well.

 

Do you guys know if its possible to tap the OEM sensor to pick up coolant temp signal? I have a Zeitronix unit, and the reads 0-5 volts. I've been curious about this for a while.

 

looks like it turned out great i plan on adding a pressure sensor for my pro efi ecu to monitor as far as a temp sensor goes would there have been anyway to wire the factory one to pick up the aftermarket units signal ?

 

I'm sorry chu and mrboost05, I don't know the answers to your questions.

Just wanted to update this thread and report that I've now put a few hundred miles on the car, including some racing events where the cooling system definitely reached a high temperature (about 206 degrees peak according to the gauge) and the tapped thermostat housing didn't leak at all.

I did use Permatex high temp thread sealant when I threaded in the sender for final assembly... I prepped for the sealant by spraying the threads out thoroughly and repeatedly with brake cleaner to ensure most if not all of the WD40 I used as "tapping lubricant" was cleaned out:

http://www.permatex.com/products/pro...sealant-detail

Here's a shot of the tapped T-stat housing installed in my engine bay, before I reinstalled the thermostat itself and the upper portion with the radiator hose outlet pipe:

 

respect for craftmanship but stm sells top part for $50 with bung welded in.

 

I like STM; I've used them several times for OEM parts and other stuff. They offer a great selection of parts and excellent customer service to boot. I didn't realize they sold a modded OEM thermostat housing top with a bung for a sender:

http://www.streettunedmotorsports.co...emp_sensor.htm



However, having the sender in the top half of the T-stat housing means your reading temps AFTER the thermostat. In the rare situation that the thermostat sticks closed, your coolant gauge will be reading cold/normal temps, while your engine will actually be massively overheating. Not what I wanted.

There is a very good reason Mitsubishi put their coolant temperature sensor in the BOTTOM of the thermostat housing, before the thermostat, and not after it.

 

^^makes sense of course.

 

Makes very good sense. Your's looks very clean tho. Job well done!

 

Jeez too many critics.

Nice job for thinking out of the box!

 

A9 tapping fluid is the stuff to use for tapping aluminum. Good job on your setup.

If the sender was located after the thermostat and the thermostat failed, wouldn't the fact that the gauge would be reading very low a sign that there is a problem? Obviously if the engine had been running for a few minutes and the temp never came up there would be an issue. Just a thought.

I will be replacing my OEM sender with my aftermarket. I don't feel the need for two gauges, and don't want to rely at all on the OEM one any more.

 

That is a valid point. Now that I've done a couple hundred miles on-track with the car, and monitored the aftermarket coolant temp gauge during these laps, I have a good feel for what's normal... within one hot lap, temps are up to 200 degrees, and on a hot day, it would be odd if it didn't continue to climb up to 205–215 F, depending on how hard I'm driving the car and the exact ambient air temps.

However, it's possible I'll get into the mode of trusting that the car isn't having any kind of cooling issue until I see the warning light I programmed to come on at 216 degrees... in this case, with the sender located after the thermostat, I would totally miss the obvious signs that something was up. Basically, I don't trust myself to be aware enough while distracted under racing conditions to catch on to this kind of situation.

I agree it's fairly pointless to have two coolant temps. The main reason I left the OEM gauge/sensor in place is because I wanted to find out what range of temperatures the OEM gauge shows as "normal," without ANY movement of the needle from the "1/3 up" position. I now know the OEM temp gauge indicates "normal, fully warmed up" from 160 degrees, all the way up to 210 or so... a 50-degree range of buffered readings!

Proof positive that the OEM temp gauge is basically only good for indicating when your engine has already been overheating for several minutes, and engine damage is impending.

 

Nice work and very clean. Quick question though, the existing temp sensor, the one that looks very similar to the one you put in---why didnt you just tap into the wiring on the existing sensor and use that signal for your light. Just curious?

 

It's possible but unlikely that the OEM coolant temp sensor is exactly the same specification as the sensor supplied with (and assumedly calibrated to work with) the Speedhut coolant gauge. Also didn't want to take the chance of damaging my brand-new gauge by plugging in the wrong sensor to it.

 

Just FYI, I don't think the OEM sensor is 1/8 npt. I think it's 1/8 bspt.

 

Ya know.... an easy way to add a sensor is make a metal pipe to put in your upper rad hose. The just weld a bung to it. Done.