Coolant light comes on

Chevrolet Impala 03,
all air in the RAD and loop must be removed, and if not the
ECT the heat gauge lies. to you;, so will PCM scans PID= ECT lie to and lies to the PCM . air pockets full of steam LIE.
so learn to let the engine cool off fully first
no engine told at all. 3.4 or 3.8L
the left side of the RAD is its cap, an new cap is cheap. and due.
take cap off fully cold, and must be full if not put in the correct 50% premixed coolant here, do not mix HOAT with others. color kinda a clue but dang not truth. ORange I think new.
but this is listed with all types, mixed.
PRESTONE AF3100 {AF3000} Prime Extended Life All Makes All Models Antifreeze/Coolant; Prime® Extended Life; All Makes / All Models; 1 Gallon
PRESTONE AF2100 {AF2000} Extended Life, Full Strength Concentrate; Extended Life; All Makes / All Models; 1 Gallon
the fill 1/2 the overflow tank with same and all hose on it and in it are not damaged.(missing, clogged, bent)
cap on.
1: see chocolate milk for oil dip stick end or OMG transmssion stick>?end.
2: see steam at rear tail pipe , hot engine ,warm day.
3: see carbon dust or oil drops floating in top of RAD NECK cap off dead cold safe engine

all that is DIY simple there are lots more tests using TOOLS.

quote4
leaky coolant overflow hose
what hose?, how wrong, fell off, say fell off,
ir blew off from hot steam that is very low coolant and or
just a bad thermostat or bad water pump , is pump belt OK?
frankly any 03 themostat is bad, they have 7 year design life.
even a thermostat that acts in random. a true risk running it here.

beyond this.
rad leak down tests
engine compression near equal and at spec,
scan tool scans, see what it shows. for sure ECT sensor reading wild and RAD full my be bad thermostat, or bad water pump
if see rust in coolant the pump impeller blades can be rusted down.
assume the best, find the low hanging fruit (failures and easy tests)

3.8L V6, (from old 3.3l ) OHV ,push rod simple )
same car as one of mine, same engine, mine is 08
p0300 means all 6 cylinders fail or combustion pressure, weak.
at random.
so not 6 bad spark plugs news and gaped to speck
so is bad fuel?
so is 6 clogged injectors,, NO.
hot engine has normal idle rpm 800 or screams only.
yes that is called gross misfire and lost of engine power too you forgot to say.
got AF radiator water in the oil pan , looks like like chocolate milk?
mine has 100k runs like new, water pump only failure ever, 100k miles me.
seems like bad fuel to me. ,diesel put in to gasoline tank?
the only weakness this motor I know is 2.
1:lower manifold gasket leaks and AF coolant falls to top of engine and down.
replace coolant every 5years is win to avoid that.
2: egr failure sticking open and a pain to reach, unless right finder pulled fully
im sure compression tests pass at 150psi up. sure. 50k miles how can it fail.?

make sure at AM dead cold engine, rad cap off rad neck is 100% full of AF.
never let it drop, and keep side tank 1/2 full cold.

never forget to burp the coolant here as you replace it all

as you fill it up.(AF antifreeze coolant)
hose off here, heater)
fill rad until it leaks here
hose back
then fill rad full to top of neck.




https://drive.proton.me/urls/2AJBWHFE3R#n9DXuC8sIcOD

link is new pump installed steps PDF

When its cold remove the rad cap, start it up, put your heater blower on full and full heat on, then when the engine gets hot look inside the rad you should see the water flowing. If its not flowing feel the top of the thermostat housing/rad hose it should be nice and hot, it its not your stat is not opening. Are you sure you got the correct temp stat for this car? Was it properly installed and is the system full with no air in it? You can also get a melt stick from your local Napa, making sure its the right temp stick for your car, put it on the stat housing and see if it melts. If it does and you still have no flow either its stuck closed, or its the wrong temp stat.

Remove the thermostat temporarily just for a diagnostic strategy. Put the thermostat housing back on with a new gasket and then drive it for a time to confirm that it is no longer doing that same thing. You will be running too cool to leave the thermostat out and you will have little or no heat. I just want to know if removing the stat helps before I continue. let me know.

no, not special but you failed to stated engine, there are many engines.
and some are very tricky here, like 2.0L.
First state the symptoms,
your post states its overheating, then no heat. (why?)
old post. but others might
Ill post , overheating ,
Example if me, with overheat.
I see my dash gauge, show overheating and engine power drops and pings, then steam vents from the rad, cap?
Over heating (ill skip cab heater but on 2L this path blocked causes thermostat to go quite nuts. not posting engine, makes this hard.)
1: full of 50% AF (antifreeze)
2: new thermoSTAT they age and fail fast. so get a new one.
put STAT in with the wax slug down, and jiggle bleed pin forward.
get air out of system after filling, (RTM)
start car, and....
4: then using and IR pyro gun we then check that
the thermostat housing hits 170F min. but not too hot.
run motor till top rad hose gets too hot to touch 180f is normal.
I had to drive 10 miles, to get it up to 180F.
my car has the hotter, 195 STA,T so runs at 195f. (helps cooling)
USING the pyro gun , the top and bottom of each rad tube.
This tool is Amazing.... and saves burn hands.
if the bottom of any RAD tube is way less than the others?, that is
a clogged UP rad tube. solution is , NEW RAD.
Usually rad repairs, are more costly than new. IN USA.
The water pump must spin at full speed, belt tight.
The impeller or some suz, motors likes disappear. from electrolysis action. so not looking at the impeller is a FAILURE on the mechanic side.
if this car has 2.0 I-4 (4 banger) it has a coolant tube on the rear
of the STAT housing, this tube must flow coolant at all times.
if it dont, the thermostat , will go nuts.
nuts means, that insufficient flow passes the thermostat wax block
causing the thermostat to cycle in a wild and random way.
I dont like this design but is reality. If applicable.
post country, post engine type and state the symptoms.

1) Your car should have a thermostat regardless of what your mechanic says. Fuel injected vehicles run better and more efficient at proper temperatures. So re-install thermostat properly before step 2.
2) Did the mechanic make sure the heater was on high temperature and blower on when he re-filled the cooling system?
Maybe not. So start engine when cool and rad cap off. Fill rad about an inch from the top and let the engine run up to normal operating temperature and keep an eye on coolant level in rad and keep it topped up as it's running. Rev the engine slightly for 5 seconds or so every once in a while to help with flow and pressure to make sure coolant is getting to and through heater core. Keep observing flow in rad to make sure it's good, when thermostat opens. You won't see much movement until thermostat opens at normal operating temperature, then you should see flow in rad and shortly after, rad fan should come on.Leave rad cap off and heater on until the rad fan comes on and off 3 or 4 times to make sure all air is out of the system. Then, make sure rad is topped up, put rad cap back on and fill return bottle to proper level. If that doesn't cure your overheating, then something was done wrong, or you have a possible head gasket problem but proper diagnosis should be done by a competent mechanic. What was the car doing initially to warrant these repairs, overheating?

From your explanation it seems you are not loosing coolant so I would rule out a head gasket at this point. I would however check the "new" thermostat. Remove the thermostat and put in pot of water. Use a thermometer that will read the boiling point of water (212F 100C). Heat water and whatch that thermostat opens at its designed temperater. You can also see if the thermostat is opening by removing the rad cap when eng cold - start you eng and see if the coolant flows in the rad before the dummy light comes on. If the coolant does not flow your thermostat is stuck or improperly installed. Also be sure that your rad cap is of the proper number of LB rating for your vehice. The steam from your exhaust is normal at cold start up - it is simply condensation evaporating. That is how you can tell if a person has not let their vehicle warm up. If you follow them it will stop after vehicle reaches operating temp. Please let me know if this helps.

Have you pressure tested your rad cap? It may not be holding the proper pressure. Also, is the rad in good shape? Are the rad fins in good shape & is the coolant in the system circulating properly. It is possible the new water pump impellor is slipping. When engine is cool, take rad cap off & start the engine. Check for coolant circulation in the rad when thermostat opens. Is it flowing freely without restriction? Top off the coolant again , you may have a vapor lock. Hope this helps. Good luck!

Check your your radiator cooling fan should come on at about 220 deg. and off at about 210 deg. at idle with a/c off, if it stats to over heat turn a/c on, fan should come on right away, if it dont check voltage at fan motor, if you do have voltage, you have a bad radiator fan motor, more then likely the reason it don't over heat while driving is air is being push through radiator where it cool's the coolant before it goes back into the engine, at stop's no air running through and never cool's coolant .

is your water pump circulating the water nissans used to have a problem with impellers on pump
leave rad cap off and run enginge should see water circulating when stat opens