I have a 2002 Accord V6 Coupe

Last week I replaced the timing belt, water pump, tensioner, and idle pulleys. When I refilled the coolant I thought I had done everything correctly, opening up the breather bolt in the back of the engine and waiting for the coolant to flow out before closing it. After getting it started back up and driving it a few times, everything seemed ok. That was 5- days ago..a couple of days after that I started to hear water (coolant) running through the block when I start for the first time of the day...at one point the other night I was hearing water sloshing sounds behind the passenger airbag area and what sounded like a straw sucking a milkshake from the bottom of a cup after it's gone...just more muffled sounding.

I use my car for uber eats. I work 12-hour nights and drive her as easy as I can..but I tend to work 5-6 days a week. I worked from midnight last night and finished today around noon.
When I got home, I noticed coolant on the ground running from under my front bumper. I popped the hood and my coolant reservoir was full and overflowing.
It looked like it was forcing itself out through the reservoir cap threads.
I have continued adding coolant to my car the last few nights before work because when I take the radiator cap off I can tell the radiator is not full. Maybe I added too much? Maybe the bubbling sounds after the water pump change means there is still air in the system?

Here is what I am really worried about though- A month or so ago I was replacing some lights in my gauge cluster (out of the car) and removed the orange/red indicator needle of the temp gauge. Well, I didn't look at the orientation of the temp gauge needle before I removed it, and when I reinstalled the cluster in my dash and got the car running and warm, the needle stayed resting against the peg in its home position (cold).

I realized I probably didn't have the needle rotated enough on its post so I carefully popped it off again, adjusted it and reinstalled it in the dash. When the car warmed up, the gauge rotated and stopped at the same place it always had, which is just a hair under the halfway point or right in the middle. So it looks like it is working normally again.... but ever since then, it has not risen above that same point after the car warms up. It seems odd that the needle is ALWAYS in that same spot after the reinstall(s).
I am hoping that I didn't reinstall wrong again and the gauge is giving an artificially low reading.

Does anyone know if the computer/OBD system reads the gauge or does it get "raw" info from the ECT sensor? Would there be other indications of an overheating condition in the form of check engine lights, etc if the engine was overheating and the temp gauge is giving a false reading? The car has never overflowed coolant from the reservoir or anywhere else for that matter.

Based on this post does anyone want to take a stab at what the issue is likely to be??? I am so stressed I can't sleep.

I am brand new to this forum and this is my first post....thank you so much for any help it is GREATLY appreciated!!!!