I have Andersen Storm Doors that have this door closer on them.
https://parts.andersenstormdoors.com...ers__53.0.html

The house is 11 years old, I bought it 5 years ago.
About 3 months ago the storm doors started to not close properly. They took forever, and wouldn't completely close unless you pulled hard on them.

I tried the top and bottom parts separately and found the problem was with the top part. It has brown crud at a seam, so I figured something was leaking out and it needed to be replaced; but first I played with the adjustment screw and found that when I set it to close slower it worked just fine.

So, I am good for the moment, but why did it work at one setting for 10.5 years and then need to be adjusted? Is something leaking? Will it need to be replaced.

The second issue is that the two doors (it is a french door unit) would often bump each other. I found that each door was attached to the frame with 8 screws. NOT ONE SINGLE SCREW WAS TIGHT. Some were just loose, while some were out an eight inch.
Do screws loosen over time? Was it on purpose for some reason? A crappy installation?
One door is used a few times a day, but the other is bolted closed and only opened about once a year to get something big in.

Any insight to these mysteries would be appreciated.

(and yeah, the title is a pun)

 

Time and weather can affect the working of the pistons, as you have evidenced. Hopefully you will get a little more action before you have to replace them. The MAIN screws that must be installed on a storm door are NOT on the face, but into the jamb with the door opened. If those screws are not secured, it will tend to pull the others out and the door will sag.

 

Issue one. Nothing lasts forever. Things change through wear and tear, or simply from age-even if rarely used- so it is no surprise if something that has an adjustment screw might need to be adjusted from time to time. 2 closer systems need to be adjusted so they work in tandem. If one closes faster than the other or more slowly than the other due to age or being out of adjustment, you might potentially have problems that develop fRom them figniting each other for dominance. The only way to know is to disconnect them from the door, pull them both out at the same time, and let them go... or time them with a stop watch.

Each door closer has a final "latching speed" which is the final jerk the door should make to pull the door shut. This is where a slight adjustment is made. The top closer is mounted slightly farther from the jamb than the bottom one so that the door actually gets two quick jerks a split second apart. This supposedly helps latch the door better than if they are exactly the same timing.

Yes, screws can loose over time. As the door operates it puts back and forth stress on the frame which can rub on the screw and there's probably a 50% chance it could turn it lose, depending on where the friction is. Or, if it is an aluminum door, with screws into aluminum, not wood, it could be that the holes or the screws are slightly stripped or elongated... no longer tight. Aluminum is soft, so a lot of back and forth movement could elongate the hole the screw is in.

Issue two. Your doors hitting in the middle- if not corrected by tightening the screws- could also indicate the hinge is slightly bent. Don't know, can't tell without being there. As mentioned, aluminum is soft so what I often find is that the hinge z-bar will distort at the top hinge, meaning the door is no longer perfectly plumb... allowing the door to sag which causes it to rub on the leading edge. This can sometimes be counteracted at least temporarily by straightening the hinge again with a block of wood and a few well directed blows from a hammer. Other times, the doors just need to be taken off and reinstalled because things can move over time and get out of adjustment.