Hi all, I have honda accord 95 4 cylinder.

Today, I drove my car for 20 mins on a hot day at low speed. I stopped my car in the garage allow to idle. Then I checked under the hood, I saw no radiator fan on or coolant boiling sound. But moment I stopped the engine, my radiator fan kicked on and off randomly for 5 mins. During fan was on I unplugged the ECT switch A by the thermostat to measure resistance continuity. The resistance was still high max 1 K ohms (no change from cold engine). But my fan keep running on and off. It did same thing for ECT switch B, too. I heard coolant boiling sound and raised its level in reservoir almost to the top of mouth. Is this normal? Is my ECT switch A still working? I guess when engine was running, coolant was circulating. But moment the engine was off, hot coolant sat at one place and boiling sound could be heard. This might have triggered radiator fan on?

The coolant at lower hose and upper hose was hot. So, I can determined that my thermostat is working, right?

Thanks and appreciated your help on this.

 

You never mentioned if you checked to see if the gauge was showing that you were overheating when it was idling. My guess is that it was. Sounds like you need to replace the fan switch(switch A). The other one is doing it's job. You should have a compression test done to see if there was any head gasket damage.