Fans on 00 impala taking awhile to come on, temp gauge gets in middle before they come and even then their on briefly

Open the hood, remove 2 plastic pins & cover just below the windshield on passenger side. There should be a preformed long rubber gasket that diverts any water away from the cabin filter (regularly replaced) found underneath in the compartment & sometimes the rubber becomes dislodged when changing the cabin filter.

It could be the thermostat but you need to check the fluid level and for any leaks (these could even be pin hole) first. If you have one of those infra-red temperature gauges you can check the temperature of the cooling system in the engine bay to double check. Generally the engine temperature should not go much about 90 deg C - this is when the electric cooling fans kick in - are these turning on?

fans came late on those car,like 212 and second fan comes on at 224,you reprogram it to come a lot sooner,,other thing is there might be gunk inside the block,and coolant has hard time to pass through,and staying longer than enough in block temp goes high,even tough the radiator is doing it's job,it is just coming out block lot hotter than it suppose to be,and gauge read the block not the radiator

replace the fan relay because if the points are stuck , the fan will be getting power all the time
easy check when the fan is running , pull the relay and the fan will stop
put it back in and if the fan starts up again , it is the relay

as I have not seen this problem as you described I have worked on a caddy ac unit before that worked for little while and shut off replaced a few parts but when all was said and done tunrs out it had a small hole in condenser in front of car grille and some of freon leaked out even the new stuff I added


that's why it worked for a while as it took several days for freon to leak out could not have found leak if not for a freon detector I had borrowed from a friend it was that small ! dye did not work

You can easily install an aftermarket temp guage. Autometer makes some nice ones.
Also, find another shop. they should have told you what was wrong and advised you not to drive the car until it was repaired. To let you go in a car in that condition is irresponsible and maybe even unethical.

The range should be in the temp range of your thermostat within in a few degrees, you probably have a 190 degree thermostat. As the outside (ambient) temp rises it's normal for the engine to run a little hotter 200 degrees is safe with coolant, water boils at 212. Your fans should cycle, so it sounds like your temp sensor is faulty. if you haven't flushed your radiator and changed your thermostat lately, now would be a good time to do so. Hope this helps,

I would look for debris around the thermostat or maybe flush and fill the coolant system to try to make it work more efficiently.

Have you check rad fan operation?

If it stays in the middle even after the car has cooled off over night,the gauge is bad,
if it starts at the bottom and moves up to the middle and stays in the middle after the car is warmed up to operating temp,then you don't have a problem,it is normal.