Hi! My 2016 Explorer has the check engine light on, and when I got it checked, they said I need to replace the catalytic converter. I haven’t been able to do that yet because the shop quoted me $1300. Recently, I also found out my brakes need to be replaced, and now my car overheats when it’s idling. My husband replaced the coolant last week, but it’s already empty again. What could be causing this? Could it be related to the catalytic converter issue? 
It sounds like your water pump has failed. Unfortunately, that’s another expensive repair, around $2500. You should stop driving the car immediately because the coolant is probably leaking into the engine. If you’re not seeing any fluid under the car, that’s likely what’s happening. You’ll need to have it towed to a mechanic to confirm, but it’s looking like the water pump.
Oh no 
I had the water pump replaced about 3-4 years ago when I first got the car. Can I just add coolant and drive it to the mechanic? It only overheats when it’s idling.
Overheating is just part of the problem. If coolant is leaking into the engine, it can cause the cylinders to crack, and that would turn a $3000 repair into a $12,000 engine replacement. You really need to have it towed.
Thank you! I called AAA, waiting on the tow now.
Good move. At least the catalytic converter can wait a little while. The car will run poorly, but it’ll run. The water pump is the bigger issue right now.
Yeah, it’s just frustrating because I already replaced the water pump shortly after I bought the car 
Maybe you’ll get lucky and it’ll just be a gasket issue or even something like a worn radiator cap. I’ve had similar symptoms in an older Explorer and it turned out to be a simple fix.
Definitely sounds like the water pump has failed, and the coolant may be leaking into the engine (crankcase). You might also want to check if your active grille shutters are working. If they’re not opening when you’re idling, that could be why your car overheats at idle.
Yikes, that all sounds terrifying. Waiting on the tow truck now 
How many miles are on your Explorer? When did you last replace the water pump?
It has 150k miles. The water pump was replaced shortly after I bought it, around 90k miles, about 3-4 years ago.
Good to know. The part itself isn’t too expensive, but the labor is where it gets pricey. Hopefully, you’ll get it sorted soon!
The dealer did the replacement and said it was an original Ford part. The mechanic shop will call me tomorrow with the diagnosis, though 
Sorry to hear that! I’ve got a 2016 Explorer too (with the EcoBoost 3.5) and I’m at 134k miles. Fingers crossed mine lets me know before it blows up!
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Stop driving it right away. You’re going to destroy the engine, and replacing it costs close to $10k.
I already had it towed to the mechanic. Still waiting for the official diagnosis tomorrow.