This article is one in a series that have been released in conjunction with Wayne's book, 101 Projects for Your Porsche 911. The book contains 240 pages of full color projects detailing everything from performance mods to changing your brake pads. With more than 650+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any Porsche 911 owner's collection. See The Official Book Website for more details.
Make no mistake about it, reinstalling glass into your car is not an easy task. There probably isn't a Porsche shop out there that won't admit to breaking at least one windshield trying to install it. The trick is to have plenty of patience, and to make sure that you don't put any excess pressure or loads on the glass. However, the process of installation requires that you push slightly on at least part of the glass. As the glass ages, it can become very brittle, and may crack a lot easier than a new windshield. Unfortunately, you may end up doing everything right and still break your windshield.
The procedure for the installation of the front windshield is similar for the other panes of glass in the car. The main difference is that the front windshield is very large, and has an increased tendency to crack because it's much longer. The length of the glass may actually magnify stresses and forces placed on the windshield. The side windows and rear glass are less susceptible to cracking. However, the rear window needs special consideration because of the defroster wire that is running through the seal. For the remainder of this project, we'll concentrate mostly on the front windshield, and then give hints and tips on how the other panes are different.
The first step in installation is to attach your rubber seal to the edges of the glass. It's really not a wise idea to recycle an old seal, as these were probably damaged in the glass removal process, and will not seat properly. Always use a new seal. I also recommend that you only use OEM German rubber when replacing your seals. I've found that most of the cheaper, reproduction seals are of an inferior quality. It's not worth it to save a couple of bucks, only to have the seal leak on you at a later date.
Before you install the seal on the glass, make sure that you place the windshield on a scratch free surface. An old rubber tire with a blanket tossed over it makes an ideal candidate. When you fit the seal to the glass, make sure that the orientation of the seal is correct. The groove for the aluminum bezel always faces towards the outside of the windshield. Using a bit of soapy water on the edges of the windshield may help with the installation of the seal.
When the windshield is to be installed into the car, a strong cord is used to properly pull the edges of the seal inwards. The cord must be inserted into the inner ridge of the seal prior to placing the window on the car. After the seal is properly mounted on the windshield, thread the cord into the channel groove of the seal. Refer to the diagram that accompanies this project for a better indication of where it's supposed to go. When the cord is completely wrapped around the outside perimeter, make sure that it overlaps itself by about 8 inches.
Now, attach the aluminum trim bezel to the seal. The trim actually helps hold the seal to the glass. If the aluminum trim became bent or dented, straighten it out as you install it. It will be much easier to fix any dents or waves in the aluminum trim now than when it is installed on the car. Install the upper and lower clips that cover the gap between the two trim pieces.
Once you have the trim and the two clips installed, it's time to place the windshield onto the car. Before placing the glass in the car, make sure that all remains of the previous rubber seal have been removed from the lip of the mounting surface. Sand and paint any rusted areas that you find. Water has a tendency to seep into the windshield area, and once in there the water may become trapped and corrode the metal.
Before you place the windshield, coat the seam/recess where the seal is about to mount with some dishwashing soap to ease the installation of the seal. The soap will be able to be washed off later with some water. Now, place the glass into the car, with the lower edge going in first. Position it back and forth until the glass is centered in its recess. Then push the top of the windshield into place. Remember not to use so much force that you crack and break the glass. Patience is a required virtue here.
Move the glass around and check the gaps on all sides to make sure that it is properly positioned. Now, from inside the car, start to pull the cord out, while an assistant applies pressure on the outside of the glass. The trick is to make sure that the seal is pulled over the lip by the cord that you are pulling from the inside. If the cord doesn't pull the seal over the lip, then the windshield will not seat, and you will have to start over and rethread the cord. Make sure that you don't damage the headliner when you pull the cord out (it's very easy to do this).
The pressure applied on the windshield from your assistant is most necessary for the bottom edge of the glass, as the weight of the glass makes pulling the cord out just a little bit more difficult. It should be apparent that a weak cord for pulling would not suffice in this situation. Nylon cords like the ones used for starting lawnmowers are excellent for this task. Once the cord is completely pulled out, the windshield should be completely seated.
Once you have the glass in place, make sure that the aluminum trim is properly seated. Press it in or tap it lightly with a plastic hammer if it is not. Double-check to make sure that the seal is properly seated all the way around the windshield. If it is not, then you might be able to use a small screwdriver to pry the seal into its correct orientation. This potentially may damage the seal and the glass, so exercise extreme caution. Check the headliner inside the car, and tuck any loose folds or excesses back in under the seal.
The installation of the rear window is a little different than the front. The rear defogger wires should be threaded into the seal prior to attaching it to the car. Be careful not to damage the fragile contacts on the rear defogger window. Make sure that you place the glass into the car with the top lip first, and then the bottom lip. With the installation of the rear window, there are more sections of headliner to potentially damage. The side windows are installed in a similar manner to the front and rear glass.
Proceed with caution at every step, and make sure that you have a patient assistant. If you do break any glass, vacuum it out of your vents before you turn them on. Use appropriate gloves when handling the glass. Even thick-edged glass like the windshield can cut you if there is a small chip on them.
Prepare the window glass by placing it on a tire or soft, flat surface. Attach the seal all the way around the outside of glass. You may have to stretch and pull the seal to get it to fit. Once the seal is in place and the bezel installed, insert the cord into the groove that mates with the edge on the body. Make sure that you have about six to eight inches of overlap when the cord is inserted completely around the entire window.
This diagram shows how the seal holds the glass to the edge of the window frame. The installation cord is inserted into the seal where the lip of the chassis is located, as indicated by circle number four on the diagram. As the seal and glass are pushed against the lip on the body and the cord is pulled out, the edge of the seal (indicated by the dotted lines) is pulled over the lip into its final position. Make sure that the seal is firmly in place all the way around the edge of the window after the cord has been completely pulled out.
Installation of the glass can be a tricky process, especially with older glass. While an assistant applies pressure from the outside, pull the cord out on the inside, forcing the seal to the inside of the pinch weld lip on the body. If the seal doesn't properly seat against the body, carefully try to refit the seal using a small screwdriver or appropriate plastic tool. If you can't pull the seal over the lip, then remove the window and try again.