I already tried searching for this... The coolant light keeps coming on in my 87 T2. At first it started only on hard right cornering, but now it does it upon starting the engine. After the car warms up, it generally goes away. The problem is, I just had it flushed and filled three months ago. The coolant level is completely normal. I'm thinking it might be a bad sensor. The previous owner had the Mazda dealership fix some wiring in that general area and it is the biggest clusterfuck I have ever seen. Do you guys have any suggestions on how to diagnose the problem? Gracias.

 

I have the same car and had the same problem a few months ago.
What fixed mine was grounding the Coolant sensor... lol
One day it got so annoying I took my pocket knife cut the sensor wire and used speaker wire (only thing I had wire-wise in my car at the time) to ground it. That stops the beeping I just kept a closer look at my temp from there on...

I decided that wasn't the best solution and plugged it back and figured out the problem.

There are most likely bubbles in your radiator or tubing somewhere. So fill the coolant up (not in the overflow tank) using the pipe that goes to the radiator. Make sure it's to the brim. Crank the engine/drive it around the block and check and fill again. continue until the incredibly annoying sound goes away. I worked for me and I haven't heard that noise since I plugged the sensor back in...

 

ty, you were right... I think that my overflow hose is leaking or something, because the level hasn't changed... I added coolant directly into the aforementioned pipe, and the light is off... Thanks for the help.

 

Now that I have started repairing ECUs I can say I am totally against grounding the wire. It burns out a resistor in the ECU and possibly other things.

Fix the car right, don't micky mouse it, or you could be paying someone to fix it or shopping on ebay to get a new/used one.