Temp issues
 

I wonder if anyone has insight into a small problem I am having. I have a 1990 that I swaped a 94 1.8 into last summer. I am using the 1.6 ecu to control the engine. All my sensors are from the 1.6.
Here is the issue. The temp guage usually runs just below the center point but occassionaly it will jump to the 3/4 position. Cutting the ignition off and on will often set the guage back to its usual position which leads me to believe the sensor is not accurate. The car never overheats and the guage will return to normal position if I do nothing. Coolant is full and clean. I have run the car with the coolant cap off on an incline to rule out an air pocket. I am wondering if someone has seen this before?

My next steps include:
Flush system and add water wetter
Replace temp sensor
replace radiator

Suggestions?

Thanks,
Allen

It sounds like the OEM thermostat(2 stage) when the first stage is clogged or not working correctly. It will ride past that temp until the large section opens.

First step should be to replace the sensor. Don't swap the radiator or change the fluid yet. A jumpy gauge is almost always a faulty sensor or chaffed wire that's grounding. There's probably some universal Napa/Kragen sensor that you can get pretty cheap. Swap that out and then report back.

yep change the sensor and while yuo are at it if the thermostat is old replace it as well it's good insurance.

Thanks
 

I will check the wiring and then the sensor. Will let you know.

Thanks,
Allen

and spend the extra 72 cents on a new thermostat gasket while you're at it

FYI - I pulled the thermostat out of the neck this morning. On the way to work, I could not get the needle past the half way point. It seems my problem was a sticky thermostat. I replaced it a little over two years ago but it was a cheap-o from Advance Auto. I'm going to go get a Mazda part this afternoon.

You might consider a fail safe tstat so when it does fail, it will fail open rather than close. Then you're problem will be rough cold starts.

Good idea.
Thanks.

If one were looking for such an item would have have a part #? Are Thermostats universal-ish?