Trying to understand the coolant flow on the IS250. From the water inlet there are two big hoses that connect to the radiator. The top radiator hose connects directly to water inlet, but bottom radiator hose connects to inlet via thermostat. Until the coolant reaches a certain temperature, the thermostat remains closed, which I assume means it stops coolant flowing through the radiator. When coolant reaches set temperature, the thermostat opens up allowing hot coolant through and cooled coolant back through the inlet. Is this correct?
1. Is the bottom radiator hose taking hot coolant out and top hose returning cool coolant? or is it the other way around?
2. I am assuming by thermostat staying closed until coolant reaches certain temperature is it promote quick warming up?
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Bottom radiator hose takes hot coolant from the motor and cools it, and then the cooled coolant re-enters the motor via the top hose.
The vehicle's "quick warm-up" procedure is separate of that of the thermostat. The t-stat doesn't care if the car is hot, warm, cold; it operate in the same fashion as it was designed to do. It'll open at the pre-designed temp.