Window And Windshield Leak Repair

[ Recaulk The Window | Repair A Rusting Channel | Fix A Cracked Window ]

Symptoms

A noticeable musty odor or wetness on the floor, seat, dashboard, or you during or after rain or a car wash or in the morning (from morning dew).

Causes

The caulk used to seal the window/windshield to the vehicle has dried up, fallen out, or was not installed properly.
The mounting surface on the vehicle for the window/windshield is rusting or has rotted out.
The window/windshield has cracked.

Diagnosis

To find the source of the leak, pull up all carpeting and insulation and try to trace the water to its source. Have someone spray the car with a garden hose to help you track it down. Once you know which window is leaking, remove the rubber and/or metal trim that runs around the edge of the window. Start from the seam (typically at the bottom-center for windows, or at the top corners for the windshield) and pry it up, slowly and carefully, from the channel. Be careful not to nick or scratch the paint. Use a small piece of wood or a rag to pry against if necessary. Now, slowly and carefully pull the trim out of the channel all the way around being careful not to bend or kink it. Inspect the channel thoroughly all the way around. Look for any missing or thin caulk; wet, dirty, or slimy spots; or rusting of the channel. Inspect the edge of the window or windshield looking for any cracks or severe chips. Now go to the solution steps below, based on what you found. Please read each step carefully because even though some steps are similar to others in different solutions, they have slight but important changes. If you didn't find any rust or cracks, then you probably just need to recaulk the area of the leak. If you found any rust in the channel, then you need to repair it. If you found any cracks or chips in the glass, then you need to repair or replace it. If you found cracks and rust in the same area, then usually the cracks are a result of the rusting because rusting metal expands which puts stress on the glass.

Recaulk The Window Or Windshield

If you have determined that the channel and glass are in good shape, then use this procedure to recaulk the window.

If you found any areas in the channel that were wet, dirty, or slimy or any spots where the caulk was thin, cracked or missing, then these areas need to be cleaned out. The typical caulk used here can be very difficult to deal with as it is rather gooey. Try to get as much of it out as you can and clean the area so that no dirt or debris remain in the channel. Use alcohol, naphtha ("lighter fluid"), or mineral spirits ("paint thinner") to help clean out the channel. Choosing one that will dissolve the caulk inside will make it easier clean the area up, but be careful not to let it run down the channel and dissolve the good caulk. I would recommend using naphtha. Avoid lacquer thinner, xylene ("xylol"), and acetone because it can remove the paint from the body panels (and the channel).
Now you need to replace the caulk. If you have a caulking gun, I would recommend a tube polyurethane sealant. It is the same stuff that the window was installed with and it does a good job. You can find it in most home improvement centers. If you can't find polyurethane, then use a tube of 100% clear silicone or paintable, acrylic-latex caulk with silicone. Otherwise, regular 100% silicone or RTV in a small, hand tube will work fine, but there isn't enough in a single tube, so you may need two or three (depending how big your window is). Avoid "Silicone II", bathroom, or tub and tile caulks because they do not seem to adhere well to metal or paint and pure latex caulk because it is usually too thin.
Open the tube of caulk with a small hole so that the tip of the applicator can get into the channel. Apply the caulk into the channel so that there is still a 1/8" to 1/4" gap between the top of the caulk bead and the outer surface of the glass to provide room for the trim. Force as much of the caulk into the bottom of the channel as possible to provide a good seal. Add a small amount of caulk all the way around the window assist the old caulk in holding the trim strip in.
Now, reinstall the outside trim strip before the caulk cures. Make sure that the pieces didn't get bent when you put them in, or they will spring back out. It can sometimes be very difficult to get the top strip back in for the windshield. Use a long 2-by-4 piece of wood with a person at each end to press it in.
Use duct tape to hold the strips down while the caulk cures (read the directions on the tube). Polyurethane takes a day or two before it holds well, but you should not get the car wet for a few days.

Repair A Rusting Channel

This solution is quite involved if it is to be done correctly. There is some hefty body work involved so if you have not had experience in removing rust and re-painting automotive paint, I would recommend reading up on the subject before continuing. Repairing the rusted areas will also disable the car for a while. You can drive it around, but since the window seal is usually what holds the window in, it can be risky and often you will have to remove the window anyway to get at all the rust. If you can afford it, I would recommend having a body shop do this for you, especially if the channel has rotted out severely. The windshield seems to be far more prone to rust than the other windows.

Sort-Of Quick Patch

If you don't feel like spending the time or money to do the job right (i.e. your not going to have the car much longer or don't really care if the body is rotting out), there is a way to stop the leaks for a while. They will come back in time, though. This fix will be specific to a windshield, but can be modified to apply to any window.

Repeat step 1 in the above solution to clean out the channel in the rusted area. Also clean the rusted or dirty areas inside the car around the window seam.
If the rust has rotted through the body (there is a hole or the rusty area is spongy), then you'll have to remove what ever trim inside the car is in the area of the rust. The majority of rust on the windshield tends to show up along the top channel, so you may have to remove the headliner (ceiling) in the car at least part way.
Take a putty knife or flat-head screw driver and scrap off the rust chips and paint flakes that are in the rusted channel area. If you end up poking holes in the metal, don't worry--this is probably where the water is getting through anyway. Just try and get all the loose debris out of the way until you reach some solid metal. If the rotted area goes beyond just the channel (out into the body), be careful not to poke holes in those areas. Also be careful not the scratch up or nick the areas that still have good paint on them.
Now take a piece of 60 or 80 grit sandpaper or a very small wire brush (sandpaper works the best) and clean up the metal areas that were exposed in step 3. If there is rust inside the car, clean those areas too. When most of the rust has been removed, clean the area with soap and water and dry thoroughly.
Now you need to replace the caulk. If you have a caulking gun, I would recommend a tube polyurethane sealant. It is the same stuff that the window was installed with and it does a good job. You can find it in most home improvement centers. If you can't find polyurethane, then use a tube of 100% clear silicone or paintable, acrylic-latex caulk with silicone. Otherwise, regular 100% silicone or RTV in a small, hand tube will work fine, but there isn't enough in a single tube, so you may need two or three (depending how big your window is). Avoid "Silicone II", bathroom, or tub and tile caulks because they do not seem to adhere well to metal or paint and pure latex caulk because it is usually too thin.
Open the tube of caulk with a small hole so that the tip of the applicator can get into the channel. Apply the caulk into the channel so that there is still a 1/8" to 1/4" gap between the top of the caulk bead and the outer surface of the glass to provide room for the trim. Force as much of the caulk into the bottom of the channel as possible to provide a good seal. Apply it liberally to the rusted area and smear it around all exposed metal leaving a fairly thick layer of it on the metal. If you had a hole leading into the car, be sure you don't get caulk dripping all over your interior. Lay down some news paper, if necessary. Add a small amount of caulk all the way around the window assist the old caulk in holding the trim strip in.
Now re-install the outside trim strip. Again, if you had a hole leading into the car, be sure you don't get caulk dripping all over you interior as you press the strip in. With the strip installed, wipe any access caulk from the surface.
Now, go add some caulk on the inside of the window seam (inside the car) and be sure to cover any exposed metal. Feel free to add caulk wherever it looked like it may have been leaking, however be sure the caulk won't interfere with the reinstallation of the interior pieces you removed in step 2.
Use duct tape to hold the strips down while the caulk cures (read the directions on the tube). Polyurethane takes a day or two before it holds well, but you should not get the car wet for a few days.

Complete Fix

The complete fix for this problem requires a lot of body work which can be very time consuming. If you need it fixed quick (in about a day), try the Quick Patch above. If you just don't have the time, I would recommend having a body shop repair it for you.

If this fix is to be applied to your windshield or rear window, have it removed by a professional unless you have the tools to do it yourself. I cannot go into this because I have not done it, but I know there are special chemicals used by window installers that quickly dissolve the adhesive that holds the window in. If the rust does not seem to go underneath the glass, then you may be able to skip this step (but it usually does). If you can leave the glass in, then you'll need to completely clear out the channel around the rusted area. The typical caulk used here can be very difficult to deal with as it is rather gooey. Try to get as much of it out as you can and clean the area so that no dirt or debris remain in the channel. Use alcohol, naphtha ("lighter fluid"), or mineral spirits ("paint thinner") to help clean out the channel. Choosing one that will dissolve the caulk inside will make it easier clean the area up, but be careful not to let it run down the channel and dissolve the good caulk. I would recommend using naphtha. Avoid lacquer thinner, xylene ("xylol"), and acetone because it will remove the paint from the body panels (and the channel).
With the rusted area now accessible, you will need to repair and repaint the the rusted areas in the channel. Follow the procedures on my Auto Body Repair and Repainting page, but skip the Finishing and Polishing sections. Go to that page now.
Allow the final paint to cure for at least 48 hours. If you had the glass removed, have it reinstalled now. If you removed it yourself, you have to reinstall it using the proper methods which I cannot go into. If you left the glass in, you'll need to reseal the areas that you worked on. If you have a caulking gun, I would recommend a tube polyurethane sealant. It is the same stuff that the window was installed with and it does a good job. You can find it in most home improvement centers. If you can't find polyurethane, then use a tube of 100% clear silicone or paintable, acrylic-latex caulk with silicone. Otherwise, regular 100% silicone or RTV in a small, hand tube will work fine, but there isn't enough in a single tube, so you may need two or three (depending how big your window is). Avoid "Silicone II", bathroom, or tub and tile caulks because they do not seem to adhere well to metal or paint and pure latex caulk because it is usually too thin.
Open the tube of caulk with a small hole so that the tip of the applicator can get into the channel. Apply the caulk into the channel so that there is still a 1/8" to 1/4" gap between the top of the caulk bead and the outer surface of the glass to provide room for the trim. Force as much of the caulk into the bottom of the channel as possible to provide a good seal. Add a small amount of caulk all the way around the window assist the old caulk in holding the trim strip in.
Now re-install the outside trim strip. With the strip installed, wipe any access caulk from the surface.
Use duct tape to hold the strips down while the caulk cures (read the directions on the tube). Polyurethane takes a day or two before it holds well, but you should get the car wet for a few days.

Fix A Cracked Or Chipped Window/Windshield

There isn't much that can be done with a cracked window or windshield besides replacing it. If it's your windshield or rear window that has cracked, I would highly recommend that you have it replaced by a professional. They will usually come out to your house to do it. If you have the proper materials and skills to do it yourself, then by all means do it. If it is a side window, then you can usually remove them yourself without too much difficulty. Door windows require disassembly of the door while fixed windows usually have some trick to them. Consult your service manual on this one. Cracks along the edges of the window, especially the windshield, are often a result of body rust under the edge of the glass. As the metal rusts, it expands putting stress on the glass until it cracks. If you remove the glass or have the glass replaced, be sure to inspect those areas and repair them if necessary.

Small chips can be repaired with a window or windshield repair kit, though cracks can rarely be fixed this way since they tend to "run". Once a small crack starts, it usually gets larger due to whatever stress started the crack in the first place. The crack will always eventually start and end at the edge of the glass. If the crack has already reached the edges and is small (on a corner, for instance), then you can probably just leave the glass alone and reseal around the crack.

If the crack is small enough and any rust under the glass has been repaired, a small dab of clear silicone rubber on the back of the glass will usually stop any leaks through the crack.

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Updated 11/12/2003.