Probably should have used the syringe first. You want to get the air out of the lines first, so that it doesn't make its way to the heads. But you're probably fine. It's just that if there's air still in the lines, and you replace the head, and then the air gets to the head, you have to replace the head again.
I dismantled the machine we have here in the shop to the level of removing the ink tubing, the pipe or whatever it is called. Just want to visually check for any leaks, any air packet or anything unusual where air might come in. I was able to remove the pipe on the side of the ink tank and check visually. On the side of the carriage/printhead, i did not bother continuing as the tubes are covered from the center going to that side, i removed the printhead though. I just assemble everything back and planned to use the syringe to suck in ink along with any air on the tubes if there is. The good news, i made a test first after i assembled everything and the problem of banding was gone. I made several pages including the very same file i printed before, no more banding. The bad news is there is one more machine that's having the same problem and i don't know what fixed it or if it is really fixed in the first place.
Using the syringe is even easier than taking it apart. Just pull the heads off and do it. It literally take less than a minute.
You wouldn't be able to find a leak. The only way you would know there was a leak is if ink leaked out (this happens occasionally) or if air leaked in (this happens often). And many times, the only way to tell if air is in the line is to suck up about half of that syringe full of ink. If, while you're sucking, you get air bubbles, then you know your problem.
I dismantled the machine we have here in the shop to the level of removing the ink tubing, the pipe or whatever it is called. Just want to visually check for any leaks, any air packet or anything unusual where air might come in. I was able to remove the pipe on the side of the ink tank and check visually.
I'm back on this, and so is the problem. Again there is banding on the print, exact same scenario as my initial post. Banding starts somewhere in the center of the prints. And this time, still the gray.
The thing i did above didn't worked though, but as suggested, just manually primed the gray tube, sucked out almost 5ml and immediately replaced the printhead G-PK.
Thank you by the way to all who have shared their ideas on this especially (Kiran,engel). Good thing i have this thread before. Helped me the 2nd time around
I can't recall what kinds of diagnostics images are on this printer, but I think they'd be more help than just regular print outs. What you really need is a large block of each specific color, so you can tell exactly which ones are banding.