I bought a Wahler 4088.87 thermostat few years ago.It has no escape valve for air.
Now on the Fastlane site,the pictured Wahler has a air valve on the inner rim.while Behr t'stat does not.

On a 300E with a vertically placed thermostat,is a air escape valve necessary??
Should i drill a hole there ?

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Tom 2010 C250 4-matic Sport (Canada)

I have changed antifreeze several times on my 88 300E without the use of the bleed screw and had no trouble.

Good luck,

Some engines ( not necessarily M-B's ) are VERY hard to purge air out of.
Lots of GM V-6's come to mind.
My V-8 Mustang used to have a purge hole in the thermostat, as shown in your picture.
Drilling a small ( 0.100 " ) opening in the thermostat probably would be okay.
It's a trick I learned from a local radiator rebuilder.
After I bulged the left endtank ( plastic ) on my Chevy truck.

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2007 C 230 Sport.