1996 740 GLE wagon windshield leaking at lower corners

[saq]

My 1986 Volvo 740 wagon has had the butyl seal come completely loose in both lower corners, so there is a pretty substantial leak. I tried packing it full of gutter sealant, which held for ~5 months, and now that has come loose (likely because of thermal expansion plus not enough contact area). Ideally from what I've read I'd pop off the windshield, put new sealing in (either butyl or the new polyurethane stuff), and re-set the windshield, however everything I have looked at seems to assume either I'm dealing with urethane sealant, I know what I'm doing already, or the windshield is cracked and I'm putting in a new one so who cares if I destroy the current glass. I'm trying to figure out how to get the windshield off without breaking it (it's a good windshield, and beyond not wasting money I've heard that most new windshields for old cars are junk now), or a better way to reseal in place that might actually work.

[volvolugnut]

Old school method for removing a windshield was a thin wire with a handle on each end. A person inside and outside the windshield would alternately draw the wire through the sealant and eventually remove the windshield. I do not remember how you got the wire started. The process sometimes breaks the windshield.
I am not sure if this works on modern windows.
volvolugnut

[saq]

Would heating it up with a heat gun help to remove it or just make it more likely to crack because you'd also soften the center plastic layer of the glass?