Hello i just bought aa use honda civic 2005 and it has 150 xxx kms
i was having overheating problem and i was suggested by a mechanic to unclogged the radiator
So i went to unclogged the radiator and it was so bad that i had to buy a new one....after installing the new radiator
Everything was Fine
untill today after 2 months
I was driving on the highway at about 80km/hr
And my obd gauge started an alarm as my temp was about 115 degree celcius
I immediately pull over on the highway and poop up my hood and the lower hose was detached
I put in back
And fill it back with coolant
And drove back home and it did not overheat
Now i noticed something weird
The temp rising to 98degree celcius whilst climbing uphill and fan kicks in
And all is normal whilst crusing at 100km/hr on highway temp is stable at 92-93degree celcius

What could be the problem
The temp only rise whilst driving uphill
But the car is not overheating
Coolant temp dont go over 100 degree celcius

​​​​​​What i am getting weird is that when the machanic install the new rad the temp never went up to 98degree even whilst driving uphill

So what could be the problem
?
Please help me
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