OPEL ASTRA (CHEVY CRUZE FOR USA MARKET) 1.4L TURBO COOLING ISSUE

Hello everyone.

I am a DIY amateur living in Greece. i have an opel astra 1.4L turbo (the equivalent of chevy cruze in usa, just GM shut down the chevrolet brand in europe and uses the brand of opel for europe), and my issue is that cooling temperature on the coolant cannot come down to the normal range.
the problem started when i saw coolant leaking from the water pump, and i took the car to a local garage who changed the water pump and the thermostat. from that moment the car's behavior changed and the acceleration became quicker. then i noticed that the car reaches the normal operating temperature which is abt 90o celcius, and the thermostat opens as it should at 105o celcius. so far so good. the cooling fan kicks in and the temperature reaches down to 98o celcius, as it should as per thermostat specs. the point is that the ecu wants the temperature to drop down to 95o celcius in order to shut down the fan. i have managed to do so only after driving for really 5-10 minutes continuously, or after pushing the rpm to 3-3500 and holding it there for enough time. i am trying to figure out some possible ways why this is happening and tackle them down one by one. from what i saw on the video that danner has on youtube, the thermostat is closing at 98o mechanically, and this is indeed happening so we are ok with that. i am thinking below as possible problems, let me know your thoughts:

1-water pump is not creating enough pressure for the coolant to flow
2-blown head gasket/ chacked engine block/ cracked valve head
3-flow restriction on the engine block, or valve head, or exit, or hoses, or radiator
4-bad quality coolant
5-change of engine combustion and indeed generate higher temperature
6-air pocket being present somewhere in the engine

Just to catchup, the thermostat has been replaced with the genuine GM but i am not sure what water pump the mechanic put. also have not seen any drop at coolant level and have also performed the "snif" test which came out negative, so this makes me rule out the blown gasket/cracked block-cylinder head.

I am just trying to have a ful list of possible causes and reach down to the real problem. the mechanics here in greece are crap to say the very least. thank god i came across scannerdanner.

would appreciate to have your thoughts on this.

So the car does not over heat and does not lose coolant, but you feel the cooling fan runs for too long and that is the issue you wish to correct?

yes the car does not overheat, the temperature is within it's normal range, but when it comes to cooling the coolant temperature does not reach the temperature that the ecu wants and therefore the fan always remains on. the ecu wants the temperature to be 95o celcius and the thermostat closes at 98o celcius. i dont know yet if there is something wrong with the electic side of the thermostat, if the coil is not heating up to expand the wax, eventhough the ecu seems to be commanding for current to go through the coil.

Would I be correct in figuring that the engine in your Astra is an LUV/LUJ?

en.wikipedia.org/wiki/GM_Family_0_engine#Generation_III

Are you observing the actual coolant temperature and desired temperature on a scan tool? If yes, then I'd be curious to know what the thermostat heater duty cycle command is while the coolant temperature is at 98C. Does your Astra have a radiator temperature sensor?

If you Astra is like our Cruze, then I'd also carefully check the cooling fan. The fan has three different speeds, and the lower two speeds often fail. The result is the ECM commanding a lower fan speed and not getting it. Just watching the fan working is not enough. All three speeds need to be there.

Along with that, I'll say that none of the LUV/LUJ engines I've worked on have their coolant temperature match the desired *exactly*. There's always a difference between the two under normal conditions.

Yes the engine is the 1.4 LUJ.
Yes I am monitoring the parameters through a scan tool and at 98degrees with no further load from a/c or any other system the heater command is at 58%, and it is equipped with a radiator coolant sensor which ranges between 45 to 65 degrees most of the time.

For the cooling fan I will investigate further to check the speeds

Maybe try vacuum bleeding the coolant system since it started after the repair. I know these are hard to bleed out regularly

This is something that i've also thought and now i've ordered the kit for the cooling system check. i am also modifying a small air compressor in order to make a hose to connect to the vacuum kit