md 2 b cooling question

[make]

I noticed that my raw water cooled temperature gauge was going up and down few days ago. I replaced the impeller and found no improvement. As i took the thermostat cover off I noticed the little by pass hole on the bottom was plugged. I pushed a an awl thru it and got it open partially, Today I drilled the hole. I am waiting for a new thermostat to arrive in a day or two. As I am checking into the cooling system further I found two opposing stories about the by pass hole. Some say it should not be open on a raw water cooled engine others have done the same as I did today with a drill? Does anyone know who is right. The awl did penetrate with a hammer tap so I assumed that it was carbon. If it suppose to be plugged how does the water get around until the thermostat opens?

[Acushla]

You should have a flow round the thermostat otherwise it is a dead end and takes longer to see the engine temp, therefore yes the hole should be open. The thermostat housings are often fitted with a bypass connections so that there is a cooling water flow through the housing (bypassing the thermostat proper)to the exhaust bend so the exhaust is still cooled while the engine is still warming up but with the thermostat still closed.

Cheers Jim

[make]

Thank you, I will reconnect everything and see how it goes.