I usually drill a tiny 1/16" or 3/32" hole in a thermostat if it doesn't have one already, many do.
Don't expect it to do anything but help burp the air out, and even if turns out it's not necessary I'm sure it can't hurt.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-