My water pump replacement went OK, thought I had all bits ordered. This afternoon I did a Diesel Purge* and while the return fluid was clear, the idle sounds better to me.
When I shut the car off I heard a "ping" on the concrete garage floor and found the flat piece in the pic.
Is it vital to the fans operation? If I recall it was on the front of the fan clutch.
I would not like to pull the radiator to try and reinstall it unless it's really necessary.

(Other than REPLACING the Damn Viscous Fan Clutch setup with an Electric
"Puller" Fan setup is the Long Term solution.)

Anyway, read and View Jim's Tutorial
(Man, He sure knows his S**t)



Refill of viscous fan clutch pictures

BUT ! If y'all KEEP the Viscous Fan Clutch you'd BEST be replacing that Spring !

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'84 300SD sold
124.128

Be glad it didn't hit a fan blade and go through the radiator , sever coolant hoses , get caught in a belt or go through the hood.

Unless this spring is available as a service part ( I doubt it is ) replace the fan clutch.

Nope, I've done all of the fussing with this pain in the butt fan I care to do.

Decided to go with an electric fan instead. With the mild weather here in the Pacific Northwest I'm not terribly concerned about overheating, and a good electric should fit the bill nicely.

I understand not everyone agrees on junking the clutch setup, but I like the idea.

Since you are going to replace the original fan with an electric, this is a moot point, however, itīs not necessary to remove the radiator to remove the fan (maybe so to install an electric assembly).

The metal strip you found, which pops back and forth from temperature change - which looks severely bent and thus its falling out - is a thermostat. When the engine is cold the fan runs constantly. After the engine along with the metal strip gets warm, the metal strip bends slightly and pushes on the pin behind it, which allows the oil in the chamber to flow, allowing it to now control the function the fan by RPM.

Unfortunately, I donīt think you are going to find an electric fan with the longevity that a mechanical fan has. If this were the case, you could wire the aux fan to run at specific temperatures.

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Don't Chrome them; polish them