I'm a real dummy when it comes to testing windshield leaks. A/C leaks, heater leaks, oil leaks, no problem because I just use UV dye. But the prospect of dilution due to the large amount of water likely needed to trace down a windshield leak leaves me baffled. Not to mention if it did make it into the cabin, it might stain the carpet or fabric. I would just suggest doing a search here or maybe one of the experts can chime in.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280