Only driven it 2 times now but this is how the temp guage looks after each time I run the car this pic is after about 5mi. of driving with it still running. Also have good heat from dash. New factory Mazda coolant temp sensor and new mazda thermostat. Common issues? Guage issue? Brought my ir temp guage home from work so I can read the rad hoses temp next time I run it.

 

The water temp is read from a sensor under/by the oil filter. You could try replacing it. I'd also add an aftermarket temp gauge. Having had a motor die from overheating, I like to backup.

 

Ok I have only replaced the temp sensor on the back of the water pump housing on the passenger side I assumed that was the sensor for the guage

 

The temp sensor you replaced is for the FI system. The one you need to replace is under the oil filter.

My car doesn't get all that higher up on the gauge than yours in the winter.

 

3rd 5mi test drive tonight and used ir temp gauge found upper rad hose at 130* lower hose at 120* and metal top of rad at about 165* seems low to me but im used to normal temp of 210 in my jeep. Is this normal temps for rotary?

 

Depends on the t-stat. Do you have a 165 degree t-stat if so it sounds about right temp wise. It could be disconnected or wire is broken just take a few minutes and look.

 

If I were you, I will install an aftermarket water temp gauge for second opinion, never rely on a 20+yrs old factory gauge

 

Buy some contact cleaner and go to town on your connectors. Lots of blue corrosion came off my 79. And everything worked great afterwards. I was having a fast blinker problem and it fixed it. The temp sensor prong tends to get pretty sludgy from oil drips during oil filter changes over the years.

 

+1

Temperature all depends on the t-stat used. The unit in your car has probably failed and isn't regulating flow. Lucky for you it failed open.

 

Thermostat is a brand new Mazda 85*c (185*f) from the dealer like 12 miles on it. 85*c factory spec for thermo?

 

Are you running rich? That could affect your temp also. My bet is the sludgy sensor. You should be fine though. You could buy another gauge cluster for parts and swap it's temp gauge into yours.

 

Thats pretty much exactly where my car was running for a little while it didnt have a thermostat in it.

 

You don't say what year but the one I'm talking about is an '84.

I had the same problem except it wasn't just the temp gauge, it was all the gauges. I'd let it sit for a while and the connectors got oxidized. I had to remove the dash, (there's 2- 2 wire connectors that I believe are only for the temp gauge, I don't know what the one on the left side is for) which is a pain (there's also two circular connectors that you have to unlock by moving a plastic piece as well). but when I had it out, I removed the nuts that secured the gauges in place and also are the electrical connection. I used steel wool (without the soap some come with, a pencil eraser might work as well) and cleaned up all the traces where the nuts connected to the gauges and also cleaned the washers and the nuts up. Now all of the gauges work.

You could also try disconnecting the sender and grounding it. That should give you the maximum reading (hot) on the gauge if that's the problem.

 

The stock temp gauge does 0-160F for the first 1/8 of the gauge swing, then the entire middle area between the 2nd mark by the cold and the first mark of the hot side covers only 50 degrees. I illustrated this a while ago in a thread of mine by sticking an analog gauge next to my stock gauge and unplugging the efan and taking lots of pics as it warmed, https://www.rx7club.com/1st-generation-specific-1979-1985-18/figuring-out-temp-guage-what-degrees-positions-between-c-h-957956/ so basically a 10-15 degree operating temp difference can make your gauge look like it's reading very hot or cold. I'd chalk yours up to it being winter.

Hope this helps

 

The type and mix of coolant you have matters too. Waterless coolant like edmunds will run about 30 degrees cooler. Additives like purple ice can lower temps 10-15 degrees. Then you have standard green. Then theres dexcool. It will most likely run an engine hotter.

 

check the wiring for the sender and ensure you have an OEM Mazda thermostat installed with the jiggle pin pointing towards the 12 o'clock position. if all is well check and replace the gauge. they fail from time to time.

 

Ok new mazda temp guage sensor installed and now after its warm (upper rad hose 150* top of rad at 170* this is how it reads normal?

 

yeah that's pretty darn good. most of the time you will see the gauge just touching the water on the symbol on the gauge. i don't think you have anything to worry about there.

 

That's where mine runs when the ambient is on the warmer side. I bit lower when it's cooler out, so I'd say you are looking good.

 

So, does it work now; it was the sensor?