My dad has 2011-12 ford flex non ecoboost…he starts car and we here a knocking-rattling noises sounds like coming from the engine but it’s hard to tell…when putting engine into neutral the noise gets louder…can anyone help me with some advice…thank you
My advice his have it towed to either a good independent shop or your dealer on Monday morning. Too many possibilities, anywhere from a exhaust heat shield to a piston rod failing.
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My first bit of advice is to check the level of the motor oil.
Hopefully this is not the case with your Dad’s car, but a “knocking rattle” sound from the engine could be an indication of an engine that is about to die as a result of insufficient oil. Or, even if the oil is at the correct level, “extended” oil changes could have resulted in the build-up of enough oil sludge to deprive parts of the engine of sufficient lubrication.
How often does Dad check the oil?
How often does he change the oil, in terms of both odometer mileage and elapsed time?
(Hint: With reduced driving as a result of COVID, the elapsed time factor is extremely important)
In any event, Purebred’s suggestion–to have the car towed to a well-respected independent mechanic’s shop–is a good one. Do NOT take it to Midas, Meineke, Monro, Sears, Pep Boys, AAMCO, or a tire shop unless you want a less-skilled person working on the vehicle.
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Does the noise occur while driving? Related to bumpy roads? Should not be hard to open the hood and get a general location of the sound.
Based on this, I somehow doubt that bumpy roads are the source of the problem:
Just trying to rule out heat shield. All we have to go on is a knocking rattling sound.
I agree that we have almost nothing–via cyberspace–for an accurate diagnosis.
From your lips to God’s ears that her Dad’s car merely has a loose exhaust heat shield. 
But, I think you will agree that the very first thing to do is to check the engine’s dipstick.
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Agreed; checking the motor oil level is the first step. Normally and in a perfect world no one would run their engine low or out of motor oil but neglect has also become a pandemic.
If the oil level is full then one has to consider something a bit more serious. Rod bearing knock, valve lifter failure, or possibly a cracked flex plate. There’s also the slim possibility of a knock being caused by a failed belt tensioner.
Without hearing said knock it can be difficult to narrow it down.
Hmmmm… Two days later, no response to the questions that I posed.
Even if the OP doesn’t want to respond, I really hope that she has communicated all of our advice to her father.
Hi…I want to say thank you for the advice and replies from everyone. I apologise…this is my first time using this website and attempting to reply…I had to reset my password one million times…I will let my dad know about all the answers that were given to me
Hi…I wanted to say thank you again for replying to my message. This is the first time that I have used this website. I had to reset my password a few times to get the hang of using the site…I will definitely tell my dad about the information you gave me. I hope you and your family have a good holidays
To ok4550…I wanted to say thank You and that I appreciate the information you gave me…this is my first time using the website
Thank you so much…I hope it is the dipstick
“I hope it is the dipstick”
Very unlikely the problem is the dipstick itself. “Check the dipstick” means to measure the oil level in the engine (when not running) by using the dipstick.
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Dear ok4450
I wanted to say thank you for responding to my email. I hope my dad will do something.