Csnow, my experience with a/c UV dye leak testing tells me that the dye and coolant light up the same. I was in a situation where I couldn't tell if the UV light was showing an a/c compressor seal leak or green coolant leaking from a blind are near the water pump.

What I'm saying is that green coolant will show up bright with a UV light without dye. Maybe MB coolant behaves the same way.

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95 E320 Cabriolet, 159K