I have been a glazier for 35 years. A tip when you rebed the plastic. Caulk should only be adhered on two sides, not three. Caulk sticks to itself better than to anything else. If adhered on three sides, when under stress, the caulk will fail at the upper edge where it meets the plastic or the aluminum
, allowing water
to infiltrate. Once the old caulk is removed, you may end up with a "U" shaped trough around the plastic. For best results, you do not want the caulk to stick to the bottom of the trough, only to the two sides. This allows the caulk to expand and contract
yet maintain maximum adhesion to the aluminum
frame and the plastic. A bond breaking tape should be used at the base of the trough. I would use a silicon product such as Dow Corning 795 or Tremco Spectrum I. Check the manufacturer specifications and see if they require a primer on the aluminum or the plastic. Critical to get the two pieces to be caulked very clean and feree of oil
& grease. Also, no matter how neat you think you are, all caulk needs to be tooled, plastic spoons work well with silicone. The tooling is not just for looks, it forces the caulk into all voids and ensures good adhesion wioth the subtrate. You also do not want the caulk bead to be thicker than it is wide. This weakens the bond, does not strengthen it. Sometimes with caulk "less is more". If the void has to be partially filled, use a backer rod like ethafoam.