2006 XLT 4.0 overheating

[Billy_fowler15]

My explorer overheats randomly, for instance tonight on my drive home my car overheated 3 times, the temperature slowly ticks up to hot as i accelerate, but when i let off the gas it cools back down to normal. Also when i accelerate it sounds like I'm riding in dump truck. It sounds like the fan is working overtime. This happens sporadically. one day it'll run just fine and then the next it will start this nonsense. any help would be much appreciated!
Thanks,
Bill

 

[Tech By Trade]

Low on coolant, bubble in the system, or the thermostat is stuck closed.

 

[derfderf]

Likely beginnings of clogged catalytic converter --- the noisy acceleration kinda gives it away, unless you have a hole in the downpipe or flex pipe.

The behavior may seem random, but it is actually pieces of the honeycomb structure coated with catalyst getting blown to the back of your catalytic converter (or further down the exhaust system), blocking the exhaust flow. Driving with a good load on the engine (uphill e.g.) usually yields poor acceleration and that funky sound..
Any vac pump that can also measure positive pressure can be hooked to the front o2 sensor bung(s) to check for excessive backpressure.
-----------------------
If the thermostat was stuck closed, I would think the the car would overheat no matter what.
While taking your foot off the gas will generate slightly less heat under the hood and the air rushing by will have less heat to draw away from the engine, as soon as you stop to let it idle for any significant amount of time, there is no way to cool the coolant as the system is not circulating. Therefore it would overheat every time at idle.