A wife posting for husband, What's up with the brakes...

After changing brake pads today, brakes won't work properly. Before stumbling upon the newer generation threads, I was reading about the first and second generation Toyota s and seems they were or are having the same problem that my husband is having with his third generation 2018 Tacoma.
Like in previous threads I read, he simply changed the brake pads today. After changing them, the brakes barely worked, like in previous threads with same EXACT problem, brake was spongy, you press the brake and the pedal goes all the way to the floor. He Has to use e brake to stop, going forward(unless just rolling in driveway), however brakes work fine going backwards.** Note: When he removed the brake pad on passenger side, the piston fell out of the caliper. He bled brake line, we bought new brake fluid to replace and he fixed piston. Same situation seems to have happened to others in many previous threads I read, but like I stated the threads were dealing with 1 and 2nd generation Tacoma's. I haven't seen any here,yet, but am not too sure how to navigate this site, just joined to try and help him find some answers that would work.
We troubleshooted with some of the other recommendations from those threads with the same issue but brakes didn't get any better, same as others.
He served in Marines and has always done ALL of our vehicle's maintenance, I have Honda vehicles. Him, Ford and Toyota, he has NEVER encountered anything like this before and we both are completely like " what the heck, what or where do we go from here"! What if he goes to press the brake to crank truck with his push start, no key ignition to start or key with this Tacoma, and it won't start...or forgets to use the e-brake, don't think that would happen, but you never know...
Has anyone else had this problem and figured out the problem to be able to come up with a solution?
Any help would be greatly appreciated, thank you in advance.
The V's

 

Since your braking system is almost identical on a later model gen 2 with the front calipers being the same item. The calipers have four pistons two on each side of the caliper. You need to compress the pistons on each side, I use a large screwdriver wedged between the rotor and brake pad to push each side in then take out the old pads. By your post it looks like your husband only pushed in one side took out that pad then possibly pushed in the other side, due to no resistance from the other pad the opposite piston popped out. This caused the fluid to leak out resulting in an air pocket possibly in the main ABS system. It’s a bit hard to bleed this system without the use of a scanner that will activate it and allow you to bleed out the system. I suggest you take it to a garage that has this in order to get the complete system done.

 

If you do just a pad slap, you need to really do a mile or so of riding the brakes hard to get them to fit the shape of the worn rotors.


Edit: if the pedal is going to the floor, flush the fluid and bleed the brakes thoroughly. If it's still going to the floor, troubleshoot it. Something is leaky.

 

Get a vacuum bleeder. They are cheap if you buy the pump by hand ones.

 

There was a piston that fell out and was returned to assembly. I would think a good bleed out in in order.

 

Or caliper replacement and then a complete bleed of the system. I have done hundreds of brake jobs and can't say I ever had a piston fall out of a caliper.