MacBook Pro (13-inch, Mid 2010) fan runs nonstop after 10.13.4 upgrade

After upgrading MacOS High Sierra 10.13.3 to 10.13.4, my MacBook Pro (13-inch, Mid 2010, 10Gb memory, 2.4GHz Intel Core Duo) started whirling its fan continuously, nonstop. Even when the lid is closed and the system is supposed to go to sleep the fan keeps on spinning, albeit at a very low speed.

Additionally, once the lid is closed, the system load gets ridiculously high. Which if course explains why the fan keeps on turning and the system never goes to sleep actually. Every time I open the lid, load averages are around 70 and 80, only to go down to the usual 1.5 - 1.6 within a few minutes after opening the lid.

Before, with 10.13.3, the fan didn't spin at all without the system actually doing something like making a build with Xcode, and the system went to sleep properly every time its lid was closed. None of my newer MacBook Pro laptops began to spin its fan nonstop after the same upgrade, and the laptop misbehaving shows no errors related to fan or other hardware components.

Since a downgrade isn't an option and I'd like to keep this old friend of mine still usable for running a web browser, at least, is there anything I could do to fix this? And why am I thinking how a certain older phone models from a certain manufacturer began to drain their batteries, and all that turned out to be a bad case of planned obsolescence?