Hardware is one of my passions.
All my crunching rigs are self-made ones.
As I mentioned in other thread, I was in heavy troubles regarding tempereture with one of them.
http://www.gpugrid.net/forum_thread.php?id=4987&nowrap=true#52633

Starting point: After installing in this rig GTX1660TI graphics card, out of the box, running Einstein@Home GPU WU, it quickly reached 83 ºC!
I was not comfortable with this.

Now I'll relate a battery of measures I took for achieving temperature stibilized at 69 ºC in same conditions. That is, a 14 ºC temperature reduction.
I also like recycling. This system is mounted in a recycled old chassis recovered from scrap.

-1st step: Install a 70 mm chassis fan at the chassis upper rear, change lower front fan from 80 to 90 mm one, enlarge front bottom airtake to double its size, and install higher legs to get chassis bottom more separated from floor.


One general rule: Hot air is lighter than colder air and goes up, so heat tends to ascend to higher zones in chassis.
Everything you make to bring cold air to lower zones and extract heated air from higher zones will generally result in lower temperatures.
Theese measures reduced temperature by 4 ºC, but I still was uncomfortable with GPU temperature at 79 ºC...

-2nd step: Reorient CPU cooler from horizontal to vertical position, and modify power supply 120 mm fan from temperature controlled to permanent working at 100%.
Two tips regarding power supply modification: Please, don't do this if you are not confident with soldering, and if you don't want to loose your power supply warranty.
Reorienting CPU cooler in vertical position will extract hot air from graphics card back and direct it to power supply exhaust.


Disconecting power supply fan from its temperature controlled power socket and soldering it directly to +12V rail will bring fan to permanently working at 100%.
This chassis is designed to power supply mounting at top. The most hot (ascending) air extraction improve, the most temperature reduction will be achieved.




Theese measures reduced temperature by 5 ºC more, but I still thought I should be able to reduce GPU temperature below 74 ºC...

-3rd step: Add an extra 120mm fan at the chassis bottom, directly pointing to graphics card.
I had to drill with circular saw at chassis bottom an aperture to mount this extra fan.






This measure reduced temperature by 5 ºC more.

And when I was happy for this total 14 ºC reduction, from 83 ºC to 69 ºC running Einstein@Home... GPUGrid ACEMD3 test WUs arrived, bringing GPU temperature to 79 ºC at full load.
I don't want to think what temperatures would be reached in the original chassis configuration!
It was worth the job, and I got a lot of fun in between.

Working with recycled equipment is always challenging. The amount of work and detail put into the cooling must be satisfying when you see an improvement as you have.
I am particularly impressed by the extra steps you have taken to hard wire the fan power cabling in the Power Supply.

The GPU appears to be an ASUS TUF or DUAL series, is that right?
The heat sink appears to be a simple round heat sink (not full length heat sink). This may be contributing to the problem with your GPU cooling.

The GPU appears to be an ASUS TUF or DUAL series, is that right?
The heat sink appears to be a simple round heat sink (not full length heat sink). This may be contributing to the problem with your GPU cooling.

Extracting much heat from the chassis is a challenging task.
Your solution reduced the temperature of your GPU by 14°C, while I guess it has increased the temperature inside your PSU (by about 5°C at least regardless of the max fan speed).
Running fans at max speed will reduce their lifetime by 2-3 times. (Not to mention the noise they make.)
Increased airflow equals increased dust aggregation, so you have to clean the inside more frequently.
It's very dangerous and difficult to clean the inside of a PSU.
I use GPUs with the largest heatsink (with "vertical" fins) available, and place one or two fans on "top" of them (cutting holes on the side panel, if I use the side panel at all) to blow out the hot air through the shortest way possible.
It's not a very good idea to cool the top parts of your PC with the hot air from the lower parts. The catch in cooling of cruncher PCs is that usually the GPU has the highest power dissipation, so it's practical to have a separate heat path for this component (i.e. water cooling, or the "standard" air cooling which blows out all the hot air trough the rear grille); also it's practical to have only a single High-end air cooled GPU in a chassis.

Thank you for your expert advice. I appreciate it very much.
From my own experience working as Service Engineer, I agree with every point.

Running fans at max speed will reduce their lifetime by 2-3 times.

Increased airflow equals increased dust aggregation

usually the GPU has the highest power dissipation, so it's practical to have a separate heat path for this component (i.e. water cooling

I find easier exchanging an usually standard PSU fan than a special GPU one.

near Sahara, dust is a particular problem

I have replaced GPU fans with Case fans, cable tied to the GPU card!

Dust and pet fur is always a problem (3 cats that like sitting on warm computers)