DIY windshield replacement

[Jonathan Farrugia]

my brother has a friend that installed windshields for a while.  i talked
to him a couple of times this is some of the stuff that i think i learned.
there are three normal ways to hold a windshield in rubber gasket, butyl,
polyurethane.  if i remember correctly butyl is the messy gooey stuff and
the polyurethane should be the firmer rubbery kind of sealant.  on a
little bit of a tangent here, being from the oem automotive world capital
i can tell you that the factories us a special kind of polyurethane on the
line.  its uv cured so that it sets up properly and quickly on the line.
as soon as the glass goes in it goes into a uv curing booth and comes out
ready to go for the most part.

installation techs will have their own personal method but this is what i
saw.  use good sharp tools to cut the windshield out.  my brothers friend
cut a few windshields out of our econolines for us.  he had the normal
windshield cut out tools that you see on all the tool sites and a mishmash
of long bladed flexible kitchen type knifes for reaching down to the glass
in cars with big dashes.  cutting butyl windshield out is a pain because
the tend to reseal themselves right after you cut through the seal, so you
might have to go around a couple of times.

installers use rubber/plastic blocks or clips to get the windshield
centered in the opening properly. then when they are happy with the fit
they lay their bead and set the glass in.  i think most installers like
butyl or a combo of butyl and polyurethane.  they like butyl because it is
self healing and flexible.  being flexible is important on older unibody
cars because whether you realize it or not the chassis does a lot of
flexing.  i've seen lots of windows cracked in the rust belt from chassis
flex.  anyhow the butyl makes up irregularities well and lets the glass
move around to keep the seal, this keeps leaky comebacks to a minimum for
the installers.

jonathan