So bought a Pacifica in April noticed then it needed rotors on the back as they were worn and grooved. Had them replaced Saturday and the brakes STILL squeal when braking. Not all the time but its after they seem to warm up, both me and the guy that replaced them looked at brakes and they are plenty thick still only issue I saw was on the upper part of the pads on both sides the pads are worn more at the very top than the rest of the pad is. I assume this is because of the previous owner not replacing rotors when they replaced the pads. What else can I check to fix the sound, and should I just let brakes become accustomed to the new rotors and it will wear the brakes back in the right way or do I need to replace the brakes on the back?
Based on what you said, I assume you replaced just the rotor, and not the pads.
Short answer is, you need to replace the pads, and you need to do this immediately.
If the rotor had grooves, then the pads likely have grooves. So now the old pads are going to dig grooves the new rotors you put on there.
If either of them has clear grooves in them, you need to replace pads and rotors together.
I would replace your old pads as quickly as possible, before they start digging groves into the new rotors.
As far as squeaking, couple of things.
First, if you can, find someone who works on these cars specifically to verify there is no model specific problem. Just every once in a while, you run across a model that has a problem specific to that car, that needs a specific fix. I had a Chevy Lumina years ago, and the back rear wheel brakes were terrible, and I was told... get used to it. Don't waste money trying to make it perfect. Likely saved me tons of money.
Second, the number one error people make when replacing brakes, is saving money on the brake pads. Do not buy cheap brake pads. Buy the expensive ones, or get used to the noise.
My personal recommendation, is Raybestos or ACDelco. You want the
Ceramic pads, or
better.
View attachment 368460
Good pads will have tapers at the edge (red oval). Not a pad that is flat to the rotor. You also want the noise shims (at the bottom the metal shims).
Stay away from cheap semi-metalic pads. They are much cheaper, and routinely loud and noisy.
If you don't get the shims, then you had better get Disc Brake Quiet, which is typically a squeeze bottle, or spray on glue that you put on the back of the pads, to put against the brake calipers. Of course do not get any of that on the pad itself, or the rotors.
If you do, you need to extremely carefully clean it off, and clean the pad and rotor, until you are absolutely sure it is gone. But generally... don't get it on the rotor or pads to begin with. Back of the pad only.
I've even seen people who used both the shim, and the brake quiet glue.
The reason you need to do this, is because sometimes (read many times. So many they sell shims and spray glue) the pad will vibrate, causing a squeal.
The shim and brake quiet glue, prevents the pads from shaking, which prevents squealing.
Lastly, and I mention this because you said it was a 2007 car: Check your brake calipers very carefully. Specifically the boot around the piston. If you see any significant leakage, or holes in the boot, have it replaced.
The smallest amount of brake fluid from a leaking caliper, will drive you insane, trying to stop if from squeaking.
Here's why I say this. You specifically said that it started squeaking more, when the brakes were warmed up.
That's important. If some brake fluid leaked onto the pads (you replaced the rotor), that brake fluid seeps into the pads.
When it's cold, everything is fine. But when it warms up... that brake fluid in the pads gets warmed up too, and starts seeping through the pad.... resulting in squeaking.
Replacing the pads may fix that in the short term, unless brake fluid is leaking, and then eventually it will get in the pads, and you'll have this problem again.
Now just to recap... it could still be that the old pads, are garbage semi-metalic pads that warm up and make tons of noise. But you don't want to put on nice new expensive pads, and have it be a leaking caliper dripping on it. So make sure. Sure that you are sure, that the caliper boot has no holes, and no significant leaks.
Hopefully that helps.