Why is my MacBook Pro fan on idle at 80 degrees ? + the MacBook is idle on 80 degrees -_- (Mid 2009 13")

Try running the Apple Diagnostics (or Apple Hardware Test) to see if any hardware issues are detected. The diagnostics are usually pretty good about detecting cooling system issues. If you laptop originally shipped with DVDs from the factory, then you can boot the second DVD which contains the Apple Hardware Test.

If you don't have access to the diagnostics using either method here, then you can try making a bootable USB diagnostic using the instructions in this article (the links within this article download the software directly from Apple's servers so the software is safe to use....just make sure to select the correct version to match the exact model of your Mac):

https://github.com/upekkha/AppleHardwareTest

I haven't worked on a 2009 laptop in many many years so I forget exactly at what temps the fan speed increases. Have you accidentally used the fan app to set the fan speed?

Usually if a computer is running hot it is due to some software issue assuming the diagnostics don't detect a hardware issue. Try booting into Safe Mode to see if the computer runs cooler...if it does, it may indicate an issue with some third party software which is installed.

Gabriel-Paun wrote:

And OS X El Capitan was freshly installed a week ago so the third party software does not have what to to with the temp. Because I don't have many.

OH and only in safe mode the fan works properly (forgot to mention this too).

If Safe Mode works, then it usually implies some third party software is causing a problem, although sometimes Safe Mode will also disable some internal Apple hardware as well by not loading the necessary driver. Maybe look for a driver or app which is not loaded in Safe Mode, but is when booted normally. It may point to the item possibly causing a problem (could possibly be an Apple driver or third party software or login item).

(The MacBook Overheats even in the installer/recovery)

Not even the EFI Boot Menu controls it, just safe mode.

So it may be some hardware failure ?

That generally indicates a hardware issue of some sort although the diagnostics generally do a good job of detecting cooling system issues. The service diagnostics (ASD 3S132 has both EFI & OS based tests) can sometimes do a better job of detecting issues, but unfortunately Apple doesn't have them available for download (would be nice if they officially released them). My guess is either the hardware has degraded over time just due to components aging (saw that a lot with the MacBooks of the time at 3-4 years old, not the Pros), or there has been accidental liquid damage (I see that a lot while supporting our organization's thousands of Apple laptops, it can be difficult to detect visually even with a trained eye). Both can easily cause this odd behavior where the laptop appears to work, but not quite right.

I doubt there is anything you can do for this laptop.

The thermal paste was change but only the idle temp changed from 70 to 50 C

I don't normally see that much of a change when refreshing the thermal paste (I recall 50C to 40C). IIRC the idle temp should actually be 10C lower, but it has been a very long time since I worked on that Mac and I usually worked on the MacBooks as opposed to the Pros. I rarely saw a noticeable change during normal use since idle temps were much easier to gauge.

A mid 2009 MacBook is rather old, it could be that there is a hardware error with the fan due to wear and tear

Even if you determine the unit has a damaged component, a 2009 MBP is obsolete and not supported. Apple will likely refuse to repair it even if by chance they have the parts.

That leaves the very chancy choice of a non Apple certified shop. And considering the unit is 14 years old, the cost to repair is very likely to be greater than the value of the device. Time for a new, or newer, Mac.

Gabriel-Paun wrote:

The drivers all work in safe mode except one , the GPU Driver, may the driver be a problem ?

While in Safe Mode macOS will utilize a basic GPU driver. On some Macs you may even see slow refresh and screen tearing as well.

On windows most of the games I tried (Not too new because its pretty old and I don't want to end the GPU's life) said the the drivers have known problems , but if I am right Apple uses different drivers. Either way they worked fine , BUT they had some or even a lot of graphical glitches (this is the only problem I had with the driver so its the only example I have)(macOS has no graphical glitches)

Unless a high end GPU is used it is not uncommon for Windows' games to sometime show graphical glitches. Plus the rest of the computer must have sufficient resources to handle the game (CPU & memory). Even if you are using an older game....has that game been updated at all more recently (may happen without you even knowing if it is downloaded from a digital online store front such as Steam)? It may have introduced the need for newer GPU drivers and possibly more/better system resources.

OH and the battery is pretty much useless (not even 5 min on battery , just shuts down after 1 or 2)

Not surprising for an old battery, or even many third party replacements.

And right now the MBP is on 50-55 C on Safari with the normal fan settings (no custom rpm) I attached a screenshot of all the temp on the device and the about page, maybe it helps with troubleshooting this MBP.

Web browsing can easily cause the system to run hot depending on the website being accessed. Plus you are using a really outdated browser which may even cause more problems in that regard as it tries to render a page which now expects a higher end CPU to do the rendering....where the older browser requires utilizing software rendering instead which causes the CPU to work harder (which means more heat).

It has been way too long since I worked on this model MacBook, but I seem to recall the CPU temps tended to stay in the 60C zone for light workloads.