Do you burp your pony? D311, D315, D318

How to burp the pony motor, gas starting engine, on Caterpillar D311, D315, D318. After draining the antifreeze/coolant or refilling the antifreeze the pony engine may over heat if the air in pony motor has not been bled out.
Selected Articles from Service Magazines 1932-1950,  pg. 147

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Always

Yes

Interesting on my 112, the owners manual goes into great detail on how to drain and refill the cooling system but my D4 manual says hardly anything about it. Both are D315 engines just a year apart. My rule of thumb is that if you cannot get as much back in as you drained out, there is an airlock somewhere.