Oldsmobile/Buick Repair: Hi Nice you offer this service. I..., buick skylark, crank sensor

Question
Hi
Nice you offer this service.
I have a 1993 Buick skylark with quad OHC engine, bought it off a friend.  The car runs very nice and smooth, when it runs.
A: First noticed the temp gauge goes up to almost full, then drops down to halfway when first started.  Then it goes up not quite as high, maybe to 3/4 and back to 1/2 while driving.  No other problems till yesterday.
B: On my way home from work engine quits, like shutting of the key.  Waited for about 10min and car started right up.
C: Took it to nearest shop. They scanned auto and said the temp sensor read minus 58 degrees. Went and changed temp sensor.  Still the same, gauge fluctuates, and engine shuts down, I think after temp light comes on in instrument panel.
D: While replacing temp gauge, anti-freeze spilled out and replaced over flow bottle after finished replacing temp sensor.
E: Something strange happened, after running car for a long time, I noticed anti-freeze in over flow bottle did not get hot or went into radiator.
There is no cap on the radiator, just in the bottle.
Getting plenty heat from heater also.
Maybe thermostat problem, you think?
Also read that a crank sensor or fuel pump can cause this problem?
What do you think?

Any info will be appreciated.

Thanks
rjshenal

Answer
Hello Rj,
Thermostat is what I was thinking, or an air pocket trapped in the system.
There should be a bleed point somewhere near the highest point in the cooling system to let air out.
I also wonder about the condition of the radiator tubes, which could restrict flow through it.

And last, the water pump may not be circulating coolant.

Van