We had a leaky rear window on our Ford E350 Cargo Van. The top of the butyl seal had hardened overtime and filled with dirt, causing a drip into the inside of the van. We used silicon to reseal, but you could use butyl tape as well. It's been a month now and holding up great. Will report later on how it is holding up.

Permatex 80855 Clear RTV Silicone Adhesive Sealant, 11 oz.
https://www.amazon.com/gp/product/B00...