Q: Car overheating, rough idle, hard to start, coolant does not circulate.

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I tried to burp cooling system after supercharger install but car started to overheat. Lower radiator hose does not get hot and heater does not work. I tried raising the car up and setting heat to max but still over heats and stalls on idle. I took it to the dealership and they told me that my ECU was bad because it was giving false readings and the radiator fans would not cut on. My car has a tune for the supercharger. The hard to start and rough idling worries me that it may be more than air in the coolant at this point. Help please!

My car has 2500 miles.
My car has a manual transmission.

Hi There, It sounds like you may have two separate issues going on here that may possibly be related via the coolant temperature sensor, which is what relays the temperature of the coolant back to the ECU which then controls the amount of fuel to provide the motor upon start up. As you know, superchargers require much more fuel and timing advance than an otherwise naturally aspirated motor. If your ECU has been mapped for this, there should be no issue there, however as mentioned above if the coolant temperature sensor is not working properly, this can cause the fuel provided at start up to be less or more than needed which may cause the rough idle you describe. This may also explain the overheating issue as well. If the incorrect readings are being provided, this may also not cause the coolant fans to come on at the correct intervals.

The coolant not circulating may be caused by a clogged radiator or a faulty thermostat. As you know, the thermostat regulates the flow of the coolant in your car’s engine and controls when the coolant flows in and out of the motor from the radiator by opening and closing at specific temperatures. When your thermostat is not working properly or is stuck closed, this will not allow the coolant to properly circulate through the engine, which may cause the engine temperature to fluctuate erratically or in some cases just remain hot. When the thermostat is stuck open it can cause the coolant to circulate constantly resulting in the motor never reaching the correct operating temperature. I would suggest having an expert from YourMechanic come to your location to take a look at your car to determine what may be causing this.

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