Remove the window. Place it in an oven at 50°C (122°F) for 4 hours to boil off moisture, then inject new sealant into the edge. Risk: High risk of melting or warping.
The crack will now be sealed, but a visible line remains. Follow the "Polishing Method" above to blend the line into the surrounding area. caravan window repair
At the very end of the crack (the pointy tip), drill a 2mm hole. This circular hole distributes stress and prevents the crack from traveling further. Remove the window