I was checking my fluid levels today. My inverter coolant level is right on the "low" line (engine is cold).

I did a quick check of the pump, hoses, inverter and radiator and saw no apparent leaks, pink crystals or residue.

Or does a little bit of coolant simply "evaporate" over time? Mine is a 2007 with almost 100k miles.

I'm taking the car in this week for it's last service before my extended warranty expires. If they don't see any leaks should I simply flush the fluid and not worry?

 

When cold, it should be near the low line. Check it hot and see where it sits. As far as your other question, it is a closed system and the level shouldn't get lower over time.

 

Loss of coolant should be minimal. The reservoir tanks are open to the atmosphere so there will be some evaporation of the water content over a very extended time period. Some of the oil you lose between changes is not burned or leaked as often assumed, it simply evaporates. The lighter the oil the more is lost to evaporation.

The other sources of loss are past a defective head gasket. It can go either into the oil (should see oil level rise if significant), or it can go into the cylinder and burn. You can sometimes see the vapour in your exhaust if it is going into the cylinder. However, in the event of a failure of the head gasket the loss is likely to be significant.

Toyota says the level is fine as long as it is between low and high when cold. They recommend filling it to full (cold) when it reaches the low marker.

 

Ron,

He was wondering about the hybrid coolant. That is a closed system that doesn't get near the engine. The engine coolant however will gradually get lower over time (or quicker if they blow a head gasket).