Carpokes Porsche Forum

Removing the retaining clip for the thermostat while the water pump is installed on the engine (still in the car) is a pain. Tool clearance is difficult at best. A handful of YouTube videos on the topic show using snap ring pliers to squeeze other snap ring pliers and other such contraptions. These videos suggest it takes hours to finally get lucky and get the snap ring removed.

I, too, tried the contraption approach, suffering from magical thinking that I'd somehow have more skill or better luck. Nope.

Instead, it took a trip to Harbor Freight. For less-than-$10, I bought a long-handle 90-degree needle nose pliers. Then I spent maybe 20 minutes sneaking up on the right modifications with the bench grinder, die grinder, and finally Dremel tool sanding drum for fine tuning the points. Finally, I had the thing out in less than five minutes.

Before Modification
Notice the wide "shoulders" and normal-size points... I got the long handle one for the leverage it would provide while squeezing. The snap ring is quite thick and stiff and has a very snug fit in its groove. It takes much more force than you probably expect to get it free.

After Modification
Notice the ground down shoulders (necessary for clearance inside the thermostat housing with the tool jaws spread open), and the skinnier, rounder points... Vehicle Clearance
Give yourself more tool clearance by unmounting the power steering pump. Remove the PS belt and unbolt the PS pump from its mounting flange. Let it hang by the supply hose for now. Then, loosen the large band clamp on the PS reservoir and allow the weight of the pump to pull the reservoir down as far as practical. As a final step, while under the car again, use zip ties to position the PS pump out of the way.
Notice in the top-side picture I also removed the distributor to provide more hand/arm/tool clearance from above. I did this while originally attempting to use normal snap ring pliers and whatever small needle nose pliers I had on hand. You may or may not need to do this. Seriously though, it takes like 20 seconds to remove it so if you need the clearance, just remove it.
The opening in my snap ring was positioned at about the 2-o'clock position, which means I used my long handle 90-degree snap-ring tool from the under-side of the car (mainly so I could see the holes in the snap ring for engaging the tool). If your snap ring is positioned closer to the 6-o'clock position, you might have more luck approaching it from above, instead.

You also may consider using a 45-degree long-handle needle nose pliers. Clearance inside the thermostat housing might be a little more forgiving, and you may be able to reach different positions a little easier.

Or get one of each and modify them both.

Have your catch bucket ready. Even then, expect some coolant down your arm and in your face. Wear safety glasses to keep it out of your eyes, and make sure your mouth is shut. They say it tastes "sweet", but I don't agree.

Also, do this with the engine cold. I imagine scalding hot coolant down your arm and in your eyes and mouth is even worse.

I faced the same dilemma and found these on Amazon - relatively easy!
GHLTOOLS Heavy Duty Cylinder Snap Ring Pliers, 90 Degrees Internal Long Nose Lock Ring Pliers for Trucks Motorcycles Cars https://a.co/d/5dkih1O

No longer available, but you get the idea.