I replaced my coolant drain plug today cause it broke in half a week ago, after that I started the engine, and I thought everything was fine, until I notice the coolant temp was almost to the top. There were no buzz sound, and the engine seems to be fine. I am thinking it might be either the thermostat or the sensor, I dont think its the water pump. Need help to identify the cause.

thanx

 

You might have somehow damaged the sender when doing the drain plug. How long did it take to go up to the top? It takes at least 5 minutes for the car to even warm up at idle, so if it jumped up there right away you have a problem with the sender.

 

Thanx for the information, I think it took around 5-10 minutes. Another question, do you know where is the sensor, and is there more than one?

 

Did you replace all of the coolant ? I've got exactly the same problem when replacing my radiator. Luckily I caught it quickly and the car is idling.

 

no, I didn't replace all the coolant, I just filled up. Does that matter?