Convertibles Always Leak
by Don Caithness
Convertibles are one of the most enjoyable classics until the weather turns wet. The potential for water leaks is almost unlimited. Perhaps this is why most convertibles suffer from floor pan rust out more than their hardtop counterparts. I’m going to cover the steps necessary to correct this problem and put the wet carpet phenomenon to rest forever.
The first step is to determine the source of the leak. The GTO was first found to have a windshield leak. Whenever the car was washed water would drip down on the steering wheel. Removing the windshield moldings revealed three areas across the top where the seal to the glass was broken. The original sealing method was to set the glass on a bead of butyl rubber that was applied to the metal windshield frame. The current method requires removing all the old butyl tape, clean the channel area and apply a 5/16” bead of urethane sealer onto the perimeter of the windshield setting it carefully in place. Next you apply a moderate amount of pressure to the glass to set the sealer, reinstall the moldings and let it cure for 24 hrs. Leak number one resolved.
Still when driven in the rain, water would leak in across the convertible header, vent windows and the top of the door glass! We contacted SoffSeal from Harrison Ohio for help. SoffSeal produce some of the finest quality reproduction rubber weather-stripping for 1950’s and up vehicles. The rubber weather-stripping on the GTO was factory original so it was the perfect theater to compare the fit and quality of the SoffSeal product. The SoffSeal product has a metal core with a molded rubber extrusion just like the original. The shape of the rubber, clips and fit is better than the GM original and will probably last longer than the car. The solution was to replace the convertible top frame weather-stripping, vent window rubbers and then adjust the door glass following the factory method as outlined in the shop manual.
The pictures will outline the complete process from start to finish.
 The upper part is the SoffSeal rear side glass weather-strip. The bottom is the original GM item. The SoffSeal part is identical in every way. |
 Start by installing the first section of side glass weather-stripping. Next install the corner screw. After this the front header section is retained by plastic “push-pins”. Apply a quality weather-strip adhesive to the header bow before inserting the pins. After you complete the installation close the top until and allow glue to set. |
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