⚠️ Help - Mechanical - Alternator/Coolant Temp Sensor/Thermostat/Water Pump

[Romana_Bede]

I need some mechanical advice with my 08 Yaris Sedan.

I’ve already called the dealership I bought it from and it’s going to them today.

In October the idle was low. I called the dealership and they told me that it was the change from summer petrol to winter petrol. It was the stupidest thing I’ve ever heard, and makes no logical sense.

In February the car started hard, then the following day the battery light came on. I took it to a parts shop and had them scan the battery and the alternator. The alternator was reading at 11.5 when it should have been at 12 or 13. There was no issue with the battery or starter.

I drove it from home to work, from work to the dealership shop. The engine overheated during that trip, and it fried the coolant temp sensor and dumped all the coolant. They replaced the serpentine belt and did a coolant bleed and refill. When I drove it back home I called them back and told them that the idle was still low. They never tested the alternator after doing the repairs like I had asked them too.

For the last week it’s been making a high pitched squeal when I start the car, and the yesterday the car made the same sound when I went to warm it up to drive it home from work.

I asked the assistant manager at work what he thought the issue was. He thinks the alternator was the original problem that caused the low idle. Next he thinks the thermostat and the water pump went when the coolant temp sensor fried when the car overheated last month.

My car’s extended warranty from the dealership will cover the alternator, water pump and thermostat but not the coolant temp sensor. The shop also warranted their work for the serpentine belt.

Is this a common issue with this make and model of car? Am I correct thinking it’s the thermostat and water pump following the coolant temp sensor? What caused the low idle - the alternator?

Thank you for your help trying to sort my car. I love my car and I’m going bonkers not being able to drive.