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VStar650CL »
https://forums.nicoclub.com/vstar650cl-u299034.html
Mon Apr 26, 2021 5:01 am
For an engine to run at, say, 190F at the water outlet, the bottom tank on the radiator will be much cooler than that, generally 140F or lower. The engine is the heat source and the temp at the upper hose is the highest in the system, the coolant having just made a trip through the block and heads. The radiator is the sink, so after a trip through the rad tubes, the water at the lower tank and hose is the coolest point in the system, generally at least 50F cooler than the inlet. So the answer to your question is both. When the tranny has no load, it warms up much slower than the engine, so the "cooler loop" actually serves to help it warm up. Once it's warm, the loop serves to keep it stable at a safe temp.