If you have a little standing water try to dam it up away from the corner using a sponge or an old rag.
Repair leaky gutter corner.
Remove the old silicone caulk from the joint connection.
Rain gutter spikes or screws should be at least seven inches long and eight is even better.
Find the crack and scrub the area around it to give way for a small plastic replacement sheet to fit into place.
If clips or brackets hold your gutters check for broken clips and loose or missing screws.
You cannot add more caulking to old.
Pull it off the gutter with your fingers or a pair of needle nose pliers.
Use a commercial grade gutter sealant and simply re apply where needed in a thorough manner.
This means the caulk will not shrink as it cures.
Often aluminum guttering will start to leak from.
Cut the caulk with a utility knife.
The bond will not be permanent and the leak will eventually return.
Allow 24 48 hours dry time yes avoid any rainy days in the forecast and you should be good to go.
If the holes are larger than nail holes use tin snips to cut a strip of flashing the same amterial as the gutter wide enough to fill the area.
Feather the roofing cement out on the surrounding area to flatten any steep edges.
Clear all debris out of the gutter miter.
You first need to clean your gutters thoroughly.
Scrubbing the crack reach your gutter by using an extension ladder.
Take an abrasive pad or wire brush and scrub the debris away from the leaky area.
Use steel wool and gently scrub the crack to make the surface clean and stamped.
Apply plastic roofing cement over small holes.
In the category of professional caulking compounds the polymer and tri polymer caulks are excellent choices for repairing leaky gutters and sealing new gutter installations.
You need to remove the old caulking.
This video takes a look at how to repair aluminium guttering to a good standard that should last many years.
Finally thoroughly clean the area of dirt debris shingle granules etc so that the new repair will hold properly.
If water is leaking where the gutter and downspout jointly connect repair the joint connection.
Repair leaking joints with silicone caulk.