Hello, I drive Thumper, a white 2015 Fiesta SE 1.6

[hamhawk]

Thumper can be seen all over the peninsula, east bay, and south bay area. However, currently she over heats at idle.

 

[scotman]

Welcome to the forum. There are many cooling system maintenance tips in the maintenance and troubleshooting section.
You might want to verify that your cooling fans are still functional by locating the relays and checking that they are not fried.

 

[Eddie2011STswap]

You have to get that fixed, I had a heating issue that I should have paid more attention to and had to get a new engine, I had a seized fan that then burst my coolant reservoir and eventually warped my rods. $3600 and 2 months down I finally got it back…. And make sure you have coolant. If it feels like a furnace with the A/C on full then it’s already getting to late

 

[Handy Andy]

 

[Handy Andy]

Then it's time to round up the usual suspects...

See anything that looks like it could be the culprit?​

 

[scotman]

Once a car has over five years or 50,000 miles of use, any one or more areas can become a problem.

 

[hamhawk]

I've changed the belt(had issues), thermostat(definitely stuck closed), fan (was frozen), engine coolant sensor(still not reading right), plus I've flushed the coolant (all of it) twice. I've also changed out the relays, and fuses applicable. I really don't want to swap the water pump because that means a LOT of work and I'm pretty certain its working from my temperature readings, the coolant is definitely moving... its just not cooling down unless the vehicle is moving at more than 20-25mph. Unless the heater is on full blast, then it cools down at about 2-3F per minute.
My scanning software keeps pointing to a error with the engine coolant sensor not reading the right temp, so I'm going to replace the replacement and cross my fingers.

She's only gone into limp mode twice, and each time I stopped and turned off the engine within a minute and let it cool down, then immediately flushed the coolant after returning home.

 

[scotman]

Do the cooling fans come on when you turn the A/C on high?

 

[Handy Andy]

There is also the issue of the radiator - is it plugged?

There are several "checks" you can do.

Per @scotman - turning on your AC should turn on the Radiator FAN and also the Blower motor.

Turn off AC - turn on HEAT - does it blow hot air thru the vents?

When you're at idle - do you get heat or AC - or is it weak?

Then when you drive does it get hotter or cooler depending on the setting?

IF it does vary, then that means the water pump is shot it is not able to move enough coolant to keep the engine cool, can't push out the hot fluid to get to the radiator.- needs RPM to push the fluid thru the motor to even get heat out of it, then to the outside - and if the pumps impeller is worn, only speed and RPM push the fluid and that's too much of the wrong thing to help with your situation.

You said the thermostat was stuck shut, so that creates a backpressure and the heater core can only do so much - that may mean the water pump has, or is, failing.

 

[scotman]

There are several identical relays that serve different functions. I usually pick a circuit to temporarily borrow a relay from to verify that the relay is the culprit for the failure. If the cooling fan becomes functional,you found the problem.