Random holes

[Cageon]

hey everyone,
I'm working on bring a '90 festiva back to life.
I have two wholes that I need to plug. One is the coolang temp sensor. Which I'm debating on if I'm going to plug for now or get a sensor. But either way I would like to know the thread size for said whole.
the other, I have no idea what it is for. So I would like to plug it since it leaks coolant from it.
you can see the whole wholes in the pic.
Thank you

[WmWatt]

I have the carburetted model so don't recognize the photo. For the threaded hole I would clean it out with a brush, twisted cloth, or what have you, without damaging the threads. Then I would get out my collection of metric bolts and see if I had one which fit, again being careful not to damage the threads. Coolant temp sensors are cheap online. I replaced mine last year. Make sure you get the right year and engine as there is more than one for the Festiva.

PS If you put a steel bolt into the aluminum threads grease liberally because a steel bolt in a leaky hole will rust and the rust will imbed itself in the soft aluminum and you'll never get it out. I know this from dismallting old bicycles with aluminum seat posts and stems in steel frames whith no grease.

[1990new]

The hole on the right is the one in the thermostat housing for the cooling fan switch. The thread size is 22mm 1.5 thread pitch. It is the same as the rear axle shaft. This would work: https://www.ebay.com/itm/M22X1-5-ENG...0AAOSwqn1eNW6Y

You can plug this but if you do your radiator cooling fan will run all the time when the ignition switch is on.

The one on the left is the temperature sending unit (M8 .75 pitch) for the temperature display on the instrument panel... I you don't have this one working correctly you will not know when your engine is running too hot. There is another water temperature switch on back side of the engine in the intake manifold which sends water temperature info to the ECM (computer).