I finally got my water temp gauge installed last weekend. After doing some reading on the forum as to the best place to install the sender, I decided to drill/tap the thermostat housing in the spot where the auto tranny cars have their second temp unit.

Guys, this location SUCKS. The only advantage I can see is it's easy to get to and drill/tap without major parts removal. Why does it suck? You get little to no reading until the thermostat opens. At first, I thought something was wrong with my gauge (Greddy 52mm gauge, BTW) as it sat at full-cold as the stock temp gauge came up to temp. As the thermostat opened, bingo - needle came up to 80 deg. C within 3 seconds.

If you have a thermostat failing or stuck closed, the gauge will NOT give you feedback. I also don't like having the gauge serve no purpose as the car is warming up - that's just silly.

Installed a water temp gauge for a customer today, and made a brass T to install in the throttle body coolant line. Full range of readings, easy to install, and works great.

So, I go to install the sender in the TB line in my car. That all works well, but I can't get a 1/8" NPT plug into the hole I made in the T-stat housing! Due to the design of the T-stat housing, I couldn't get a "deep" tap with the tap wrench. Since pipe thread is tapered, the tap gets bigger as it goes along. The plug is on the large side of the scale, so it won't thread into the hole. After trying 2 different plugs, dropping one of the plugs and having to find it (tried the magnet at first, but brass isn't ferrous!), I ended up putting the plug in the brass T in the TB coolant line and put the sender back in the T-stat hole.

So, I now need to replace my hacked T-stat housing.

Moral of the story? As far as I can see, there is NO GOOD REASON to use the thermostat housing for a sender location. Use the TB coolant line - takes less time to install, no drilling or tapping, etc.

If any of you guys have other observations, please share. Just wanted to vent my frustration .

Dale

 

Just have the hole you made welded...you had the thermostat housing off of the car when you were trying to tap it right?

 

I run Evans NPG with the surrounding portion of the thermostat drilled so I always have coolant flowing through the housing.

I used to run the sensor with a T at the throttle body and the only differenc that I'm seeing now is that the coolant temp at the thermostat housing is higher.

 

Is the temp difference significant, or are we talking a couple degrees?

 

Can you take some pics of the the sender on the tb coolant line.

 

IMO that is actually good, at least you will know if your tstat is not openning up since the water wont be flowing, it's better that way...what's the big deal in watching the water temp go up while warming up the car.....I may be wrong in how I think but if you think about it your tstat will stay open in most of your driving time so it will preety much show you the temp while driving the car, if you have been driving the car and temps start going down but your needle in the car is going up then you know that your tstat is not working.

 

I think Dale is more concerned with the thermostat being stuck closed BEFORE the car warms up. With the sensor in the throttle body line, you can see the temperature rising from the very begining. If the thermostat doesnt open, you will know right away. Otherwise you're stuck with the stock gauge until the thermostat opens and shows a reading on the gauge.

 

I think you're right in many ways Dale, but it's not that big of a deal to me. Mine is in the t-stat housing, and within 2min the thermostat will open and the temps rise up. It isn't a big deal to me that I'm not getting temps for that time since I'm not pushing the car. If it goes more than 5" without rising, I will know something is wrong. Whether the engine can overheat with a stuck thermostat in 5min, I don't know. Maybe I will move that to the TB hose - it would be a cleaner installation, that's for sure.

Dave

 

You can also get rid of the sensor for the stock gauge near the oil pressure sensor and use that spot for your aftermarket gauge sensor. The stock water temp sensor in that location is used only for the gauge, so the only side effect is that the stock gauge stops working.

-Max

 

max the same goes for the oil sender. dale post a pic of where you put your sender. i have the same unit mounted to the blank hole on the right side of the housing, no air pump. mine reads fine.

 

Dale, did you install it according to this thread? https://www.rx7club.com/3rd-gen-archives-73/water-temperature-sensor-how-tap-install-247152/ or elsewhere?

I am debating with that install OR placing it in the water pump housing itself (far right). Here is a pic of where I am speaking of.

 

I did the same thing as Dale and tapped the thermo housing. I have a Defi D gauge and I thought I would have the same problem with temp. readings. I come to find out that the sensor reads temp while it is warming up. I don't know if it is the jiggle pin hole allowing some reading or the ambient temp of the housing it self, but it starts moving at 140 and slowly moves until the thermostat opens. it is nice and it follows right along with the stocker. I am not sure about other senders but mine works perfect. what about tapping the water pump housing itself, like behind where the thermoswitch is? that way it is before the thermostat. just a thought.

 

Yup, I've got aftermarket sensors for both the water temp and the oil pressure that replaced the stock sensors. And I also replaced the stock gauges themselves with the aftermarket gauges. It works great.

-Max

 

There are pros and cons to about every location. However, I've heard that the TB line can show a difference of 10-15 degrees.

IMO, I would only mount and aftermarket sensor in the thermostat housing or replace the stock sensor with it.

Actually, if the gauge never starts reading because of a failed/stuck thermostat, at least you'll know about it.

 

i tapped my water temp sender by the filler cap..had no problems here, unless thats a different story..

 

Can someone list everything needed to tap into the tb coolant line.

 

Why on earth would you put the sensor there??? Your reading the temps on the cool side before they go into the engine.

Stephen

 

I have mine tapped into the water pump housing, which works fine but seems to read a little low. Does the TB read low too?

 

Reads low compared to what? PFC reading?

Keep in mind that sensors in different locations are going to have different readings. The idea is to use the best location which will give you the best reading.

 

i think with the temp sender tapped into the thermo housing is a cleaner looking install compared to the tb hose. personally i dont think any place is bad though, if i knew about the greddy upper radiator hose with the temp sender bung. i might have considered that route.

 

Are you speaking of the picture as I posted be on the cool side (bad location)? I found the install on a Japanese webpage, I ahve yet to do mine.

 

great ideas but the best location imho is at the coolant fill housing/thermostat housing. This is going to be the hottest the water is before it goes into the radiator. If you use a location before the water has fully circulated and picked up it' s thermal load, then you may be running the engine hotter than you might think. Just my opinion, and 7 years of track experience tells me I'm right!
Art

 

I don't have a PFC but at idle the stock fans are supposed to come on at 221F and when that happens my VDO gauge is reading more like 210. Also at cruising I'm reading well under 180 (more like 165) which should be the theoretical minimum.

 

I use a greddy gauge and it works just like this also. Maybe my thermostat is stuck open?

 

Dale, you can always go to HomeDepot and pick up a 1/8" NPT plug from there... i had a sensor there and removed it, since no need with a powerFC. Worked great and cost all of 30cents to do..lol