17. Operating without a thermostat

In short, without a thermostat to control the flow, all water from the water pump is free to pass through the block and head to cool (or overcool) the engine. However, it is also free to bypass the “T” fitting on the water jacket side plate, go directly through the thermostat housing, directly to the manifold and out through the exhaust system (without cooling the engine at all)!

In cases where engine temperature is quite normal without a thermostat, it simply means that (purely by coincidence) the head loss between going through the engine versus going through the bypass loop balances out so that the ideal amount of water is taking the path through the block and head rather than bypassing. It is just as common, however, for engines to run too cool, or, in other cases, to run too hot.

It really is better to use a thermostat in the Atomic 4, and to keep it clean by soaking it in vinegar every season. - Updated: November 4, 2003