DIY Network

Replacing a Cracked Windshield A cracked windshield can present a safety hazard since the crack may obstruct the driver's view. From "Car Care & Repair" episode CCR-122

A cracked windshield, particularly on the driver's side, can present a hazard since the crack may obstruct the driver's vision. In fact, in most places driving with a cracked windshield is illegal and, technically, you can receive a traffic citation for it.

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	Figure A
	Figure B
	Figure C
	Figure D
	Figure E
	Figure F
	Figure G
	Figure H
	Figure I
	Figure J
	Figure K
	Figure L
	Figure M

Small chips or dings in a windshield (figure A) can be repaired by a glass specialist, and they should be fixed as soon as possible after they occur since they are inclined to spread and become larger. Moisture penetrates below the outer layer of glass via the crack, and then expansion and contraction of the trapped moisture (due to temperature changes) causes the crack to spread.

Larger cracks cannot be repaired. If a windshield has a large crack or is badly damaged, the entire windshield must be replaced. For cracks, a good rule of thumb is: if the crack is longer than the length of a dollar bill (figure B ) -- i.e., longer than 6 inches -- it cannot be repaired, and a windshield replacement is in order.

Replacing a windshield involvesy replacing the glass as well as the weather stripping and seal that surrounds the glass. Because of a number of safety considerations (including the fact that airbag operation is dependent on proper installation of the windshield), and because it requires specialized tools and materials, changing a windshield is best left to professionals. Glass specialist Terry Ranta demonstrates the steps in the process.

First, the windshield-wipers must be removed (figure C). The retaining nuts are removed and the wiper assembly is lifted off.

With the wipers removed, the decorative rubber strip is detached using a pry tool (figure D).

Once loosened with the pry tool, the stripping can be pulled away(figure E). This outer seal is primarily cosmetic. The actual waterproofing weather-seal is beneath it -- a urethane bead that runs beneath a black band around the perimeter of the glass.

The urethane bead must be cut all the way around in order to release the windshield so that it can be lifted out. The bead is cut using a specialized tool known as a cold knife (figure F).

The hooked blade of the cold knife is inserted beneath the glass. The knife is then drawn around the perimeter of the windshield using the cable and pull-handle (figure G).

As the knife is pulled along, it makes a carefully controlled cut through the urethane bead. Once a cut has been made all the way around the glass, the windshield is pressed and dislodged from inside the vehicle, then carefully lifted out of the opening (figure H) and placed aside. With the old glass removed, the next steps involve prepping the new glass to ready it for insertion. The reason that these steps must be done at this point is that, once the new urethane bead is applied to the opening, there is a limited amount of time for installing the glass before the bead begins to harden. With the new glass already prepped, it will be ready to be set in place.

After cleaning the inside surface of the new windshield with ordinary glass cleaner, an oil-and-grease remover is used to clean away any oily residue from the glass-frit (the black band around the outside of the windshield). A frit primer is then applied to the inner surface of the frit (figure I). Work can then begin on the vehicle to prepare it to accept the glass. By the time that the vehicle is fully prepared, the frit primer should be dry.

To prepare the windshield opening to accept the glass, the old urethane bead needs to be removed. A utility knife is used to trim away and remove at least 90 percent of the old urethane (figure J). A small amount of old urethane may remain without interfering with the new installation.

A fresh bead of urethane, also known as the windshield weather-strip adhesive, is then applied into the groove surrounding the windshield opening. The adhesive is applied using an injector, much as caulk is applied. To ensure even and generous application of the urethane, a v-shaped slot is cut in the tip of the applicator (figure K).

Once the adhesive has been applied all the way around the opening, the new glass is carefully set in place and aligned (figure L). Once aligned, the glass is pressed firmly to ensure that it's completely seated. The replacement windshield shown in our demonstration is a one-piece unit with a cosmetic strip already in place. There is no need for application of a separate cosmetic strip.

The edges replacement windshield are taped down to hold it firmly in place while the adhesive sets (figure M). After about eight hours, the tape can be removed, and the vehicle is safe to drive.

Most glass installations are completely guaranteed, so that if a leak occurs around the edge, the installer will repair the leak at no charge.

RESOURCES :

Auto Repair for Dummies
Author: Deanna Sclar
ISBN: 0764550896

Some vehicles provided by Ted Russell Ford

Ted Russell Ford
8551 Kingston Pike
Knoxville, TN 37919
Phone: 865-693-7611
Web site: www.tedrussell.com

Special thanks to Classic Auto Glass

Classic Auto Glass
La Follette, TN