100 = 1 bar = 14.7 psi
120 = 1.20 bar
140 = 1.4 bar

Your 100 cap is fine, it simply means that you can't overheat the engine as much as you could with a higher pressure cap. If you have a leak in your system (cracked tank top or whatever), the lower pressure cap is better. Mercedes tended to increase cap pressure in later models: my 123 has a 120 cap while my 124 and 210 both have 140 caps.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970